From d6299d9941644e1bb36d274597e53a4c9e12f3bf Mon Sep 17 00:00:00 2001
From: Alex Turbov <i.zaufi@gmail.com>
Date: Wed, 28 Jul 2021 01:53:22 +0300
Subject: Refactor: Run CPU/OS/Memory tests once on first run

---
 Source/cmCMakeHostSystemInformationCommand.cxx | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/Source/cmCMakeHostSystemInformationCommand.cxx b/Source/cmCMakeHostSystemInformationCommand.cxx
index 0550568..10c0714 100644
--- a/Source/cmCMakeHostSystemInformationCommand.cxx
+++ b/Source/cmCMakeHostSystemInformationCommand.cxx
@@ -45,10 +45,14 @@ bool cmCMakeHostSystemInformationCommand(std::vector<std::string> const& args,
     return false;
   }
 
-  cmsys::SystemInformation info;
-  info.RunCPUCheck();
-  info.RunOSCheck();
-  info.RunMemoryCheck();
+  static cmsys::SystemInformation info;
+  static auto initialized = false;
+  if (!initialized) {
+    info.RunCPUCheck();
+    info.RunOSCheck();
+    info.RunMemoryCheck();
+    initialized = true;
+  }
 
   std::string result_list;
   for (size_t i = current_index + 1; i < args.size(); ++i) {
-- 
cgit v0.12


From d6b4982697d74a0077f7f3c57f5078449b41e8ef Mon Sep 17 00:00:00 2001
From: Alex Turbov <i.zaufi@gmail.com>
Date: Wed, 28 Jul 2021 04:38:26 +0300
Subject: Refactor: Move module private functions on top

---
 Source/cmCMakeHostSystemInformationCommand.cxx | 116 ++++++++++++-------------
 1 file changed, 54 insertions(+), 62 deletions(-)

diff --git a/Source/cmCMakeHostSystemInformationCommand.cxx b/Source/cmCMakeHostSystemInformationCommand.cxx
index 10c0714..2a0b0b8 100644
--- a/Source/cmCMakeHostSystemInformationCommand.cxx
+++ b/Source/cmCMakeHostSystemInformationCommand.cxx
@@ -9,7 +9,7 @@
 #include "cmExecutionStatus.h"
 #include "cmMakefile.h"
 
-#if defined(_WIN32)
+#ifdef _WIN32
 #  include "cmAlgorithms.h"
 #  include "cmGlobalGenerator.h"
 #  include "cmGlobalVisualStudioVersionedGenerator.h"
@@ -19,60 +19,21 @@
 #endif
 
 namespace {
-bool GetValue(cmExecutionStatus& status, cmsys::SystemInformation& info,
-              std::string const& key, std::string& value);
-std::string ValueToString(size_t value);
-std::string ValueToString(const char* value);
-std::string ValueToString(std::string const& value);
+// BEGIN Private functions
+std::string ValueToString(std::size_t const value)
+{
+  return std::to_string(value);
 }
 
-// cmCMakeHostSystemInformation
-bool cmCMakeHostSystemInformationCommand(std::vector<std::string> const& args,
-                                         cmExecutionStatus& status)
+std::string ValueToString(const char* const value)
 {
-  size_t current_index = 0;
-
-  if (args.size() < (current_index + 2) || args[current_index] != "RESULT") {
-    status.SetError("missing RESULT specification.");
-    return false;
-  }
-
-  std::string const& variable = args[current_index + 1];
-  current_index += 2;
-
-  if (args.size() < (current_index + 2) || args[current_index] != "QUERY") {
-    status.SetError("missing QUERY specification");
-    return false;
-  }
-
-  static cmsys::SystemInformation info;
-  static auto initialized = false;
-  if (!initialized) {
-    info.RunCPUCheck();
-    info.RunOSCheck();
-    info.RunMemoryCheck();
-    initialized = true;
-  }
-
-  std::string result_list;
-  for (size_t i = current_index + 1; i < args.size(); ++i) {
-    std::string const& key = args[i];
-    if (i != current_index + 1) {
-      result_list += ";";
-    }
-    std::string value;
-    if (!GetValue(status, info, key, value)) {
-      return false;
-    }
-    result_list += value;
-  }
-
-  status.GetMakefile().AddDefinition(variable, result_list);
-
-  return true;
+  return value ? value : std::string{};
 }
 
-namespace {
+std::string ValueToString(std::string const& value)
+{
+  return value;
+}
 
 bool GetValue(cmExecutionStatus& status, cmsys::SystemInformation& info,
               std::string const& key, std::string& value)
@@ -200,20 +161,51 @@ bool GetValue(cmExecutionStatus& status, cmsys::SystemInformation& info,
 
   return true;
 }
+// END Private functions
+} // anonymous namespace
 
-std::string ValueToString(size_t value)
+// cmCMakeHostSystemInformation
+bool cmCMakeHostSystemInformationCommand(std::vector<std::string> const& args,
+                                         cmExecutionStatus& status)
 {
-  return std::to_string(value);
-}
+  std::size_t current_index = 0;
 
-std::string ValueToString(const char* value)
-{
-  std::string safe_string = value ? value : "";
-  return safe_string;
-}
+  if (args.size() < (current_index + 2) || args[current_index] != "RESULT") {
+    status.SetError("missing RESULT specification.");
+    return false;
+  }
 
-std::string ValueToString(std::string const& value)
-{
-  return value;
-}
+  std::string const& variable = args[current_index + 1];
+  current_index += 2;
+
+  if (args.size() < (current_index + 2) || args[current_index] != "QUERY") {
+    status.SetError("missing QUERY specification");
+    return false;
+  }
+
+  static cmsys::SystemInformation info;
+  static auto initialized = false;
+  if (!initialized) {
+    info.RunCPUCheck();
+    info.RunOSCheck();
+    info.RunMemoryCheck();
+    initialized = true;
+  }
+
+  std::string result_list;
+  for (auto i = current_index + 1; i < args.size(); ++i) {
+    std::string const& key = args[i];
+    if (i != current_index + 1) {
+      result_list += ";";
+    }
+    std::string value;
+    if (!GetValue(status, info, key, value)) {
+      return false;
+    }
+    result_list += value;
+  }
+
+  status.GetMakefile().AddDefinition(variable, result_list);
+
+  return true;
 }
-- 
cgit v0.12


From 69d3fcf2c866e83480730b6a3b3589edc5ba96ae Mon Sep 17 00:00:00 2001
From: Alex Turbov <i.zaufi@gmail.com>
Date: Wed, 28 Jul 2021 16:22:54 +0300
Subject: =?UTF-8?q?Refactor:=20`bool=20GetValue(...,=20string&)`=20?=
 =?UTF-8?q?=E2=86=92=20`optional<string>=20GetValue(...)`?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Also, split `GetValue()` into 2 overloads:

- one used to get documented keys
- the other (different signature) to get `VS_nn_DIR` keys
---
 Source/cmCMakeHostSystemInformationCommand.cxx | 184 +++++++++++++++----------
 1 file changed, 114 insertions(+), 70 deletions(-)

diff --git a/Source/cmCMakeHostSystemInformationCommand.cxx b/Source/cmCMakeHostSystemInformationCommand.cxx
index 2a0b0b8..4465a6d 100644
--- a/Source/cmCMakeHostSystemInformationCommand.cxx
+++ b/Source/cmCMakeHostSystemInformationCommand.cxx
@@ -4,6 +4,8 @@
 
 #include <cstddef>
 
+#include <cm/optional>
+
 #include "cmsys/SystemInformation.hxx"
 
 #include "cmExecutionStatus.h"
@@ -35,83 +37,117 @@ std::string ValueToString(std::string const& value)
   return value;
 }
 
-bool GetValue(cmExecutionStatus& status, cmsys::SystemInformation& info,
-              std::string const& key, std::string& value)
+cm::optional<std::string> GetValue(cmsys::SystemInformation& info,
+                                   std::string const& key)
 {
   if (key == "NUMBER_OF_LOGICAL_CORES") {
-    value = ValueToString(info.GetNumberOfLogicalCPU());
-  } else if (key == "NUMBER_OF_PHYSICAL_CORES") {
-    value = ValueToString(info.GetNumberOfPhysicalCPU());
-  } else if (key == "HOSTNAME") {
-    value = ValueToString(info.GetHostname());
-  } else if (key == "FQDN") {
-    value = ValueToString(info.GetFullyQualifiedDomainName());
-  } else if (key == "TOTAL_VIRTUAL_MEMORY") {
-    value = ValueToString(info.GetTotalVirtualMemory());
-  } else if (key == "AVAILABLE_VIRTUAL_MEMORY") {
-    value = ValueToString(info.GetAvailableVirtualMemory());
-  } else if (key == "TOTAL_PHYSICAL_MEMORY") {
-    value = ValueToString(info.GetTotalPhysicalMemory());
-  } else if (key == "AVAILABLE_PHYSICAL_MEMORY") {
-    value = ValueToString(info.GetAvailablePhysicalMemory());
-  } else if (key == "IS_64BIT") {
-    value = ValueToString(info.Is64Bits());
-  } else if (key == "HAS_FPU") {
-    value = ValueToString(
+    return ValueToString(info.GetNumberOfLogicalCPU());
+  }
+  if (key == "NUMBER_OF_PHYSICAL_CORES") {
+    return ValueToString(info.GetNumberOfPhysicalCPU());
+  }
+  if (key == "HOSTNAME") {
+    return ValueToString(info.GetHostname());
+  }
+  if (key == "FQDN") {
+    return ValueToString(info.GetFullyQualifiedDomainName());
+  }
+  if (key == "TOTAL_VIRTUAL_MEMORY") {
+    return ValueToString(info.GetTotalVirtualMemory());
+  }
+  if (key == "AVAILABLE_VIRTUAL_MEMORY") {
+    return ValueToString(info.GetAvailableVirtualMemory());
+  }
+  if (key == "TOTAL_PHYSICAL_MEMORY") {
+    return ValueToString(info.GetTotalPhysicalMemory());
+  }
+  if (key == "AVAILABLE_PHYSICAL_MEMORY") {
+    return ValueToString(info.GetAvailablePhysicalMemory());
+  }
+  if (key == "IS_64BIT") {
+    return ValueToString(info.Is64Bits());
+  }
+  if (key == "HAS_FPU") {
+    return ValueToString(
       info.DoesCPUSupportFeature(cmsys::SystemInformation::CPU_FEATURE_FPU));
-  } else if (key == "HAS_MMX") {
-    value = ValueToString(
+  }
+  if (key == "HAS_MMX") {
+    return ValueToString(
       info.DoesCPUSupportFeature(cmsys::SystemInformation::CPU_FEATURE_MMX));
-  } else if (key == "HAS_MMX_PLUS") {
-    value = ValueToString(info.DoesCPUSupportFeature(
+  }
+  if (key == "HAS_MMX_PLUS") {
+    return ValueToString(info.DoesCPUSupportFeature(
       cmsys::SystemInformation::CPU_FEATURE_MMX_PLUS));
-  } else if (key == "HAS_SSE") {
-    value = ValueToString(
+  }
+  if (key == "HAS_SSE") {
+    return ValueToString(
       info.DoesCPUSupportFeature(cmsys::SystemInformation::CPU_FEATURE_SSE));
-  } else if (key == "HAS_SSE2") {
-    value = ValueToString(
+  }
+  if (key == "HAS_SSE2") {
+    return ValueToString(
       info.DoesCPUSupportFeature(cmsys::SystemInformation::CPU_FEATURE_SSE2));
-  } else if (key == "HAS_SSE_FP") {
-    value = ValueToString(info.DoesCPUSupportFeature(
+  }
+  if (key == "HAS_SSE_FP") {
+    return ValueToString(info.DoesCPUSupportFeature(
       cmsys::SystemInformation::CPU_FEATURE_SSE_FP));
-  } else if (key == "HAS_SSE_MMX") {
-    value = ValueToString(info.DoesCPUSupportFeature(
+  }
+  if (key == "HAS_SSE_MMX") {
+    return ValueToString(info.DoesCPUSupportFeature(
       cmsys::SystemInformation::CPU_FEATURE_SSE_MMX));
-  } else if (key == "HAS_AMD_3DNOW") {
-    value = ValueToString(info.DoesCPUSupportFeature(
+  }
+  if (key == "HAS_AMD_3DNOW") {
+    return ValueToString(info.DoesCPUSupportFeature(
       cmsys::SystemInformation::CPU_FEATURE_AMD_3DNOW));
-  } else if (key == "HAS_AMD_3DNOW_PLUS") {
-    value = ValueToString(info.DoesCPUSupportFeature(
+  }
+  if (key == "HAS_AMD_3DNOW_PLUS") {
+    return ValueToString(info.DoesCPUSupportFeature(
       cmsys::SystemInformation::CPU_FEATURE_AMD_3DNOW_PLUS));
-  } else if (key == "HAS_IA64") {
-    value = ValueToString(
+  }
+  if (key == "HAS_IA64") {
+    return ValueToString(
       info.DoesCPUSupportFeature(cmsys::SystemInformation::CPU_FEATURE_IA64));
-  } else if (key == "HAS_SERIAL_NUMBER") {
-    value = ValueToString(info.DoesCPUSupportFeature(
+  }
+  if (key == "HAS_SERIAL_NUMBER") {
+    return ValueToString(info.DoesCPUSupportFeature(
       cmsys::SystemInformation::CPU_FEATURE_SERIALNUMBER));
-  } else if (key == "PROCESSOR_NAME") {
-    value = ValueToString(info.GetExtendedProcessorName());
-  } else if (key == "PROCESSOR_DESCRIPTION") {
-    value = info.GetCPUDescription();
-  } else if (key == "PROCESSOR_SERIAL_NUMBER") {
-    value = ValueToString(info.GetProcessorSerialNumber());
-  } else if (key == "OS_NAME") {
-    value = ValueToString(info.GetOSName());
-  } else if (key == "OS_RELEASE") {
-    value = ValueToString(info.GetOSRelease());
-  } else if (key == "OS_VERSION") {
-    value = ValueToString(info.GetOSVersion());
-  } else if (key == "OS_PLATFORM") {
-    value = ValueToString(info.GetOSPlatform());
+  }
+  if (key == "PROCESSOR_NAME") {
+    return ValueToString(info.GetExtendedProcessorName());
+  }
+  if (key == "PROCESSOR_DESCRIPTION") {
+    return info.GetCPUDescription();
+  }
+  if (key == "PROCESSOR_SERIAL_NUMBER") {
+    return ValueToString(info.GetProcessorSerialNumber());
+  }
+  if (key == "OS_NAME") {
+    return ValueToString(info.GetOSName());
+  }
+  if (key == "OS_RELEASE") {
+    return ValueToString(info.GetOSRelease());
+  }
+  if (key == "OS_VERSION") {
+    return ValueToString(info.GetOSVersion());
+  }
+  if (key == "OS_PLATFORM") {
+    return ValueToString(info.GetOSPlatform());
+  }
+  return {};
+}
+
 #ifdef HAVE_VS_SETUP_HELPER
-  } else if (key == "VS_15_DIR") {
+cm::optional<std::string> GetValue(cmExecutionStatus& status,
+                                   std::string const& key)
+{
+  std::string value;
+  if (key == "VS_15_DIR") {
     // If generating for the VS 15 IDE, use the same instance.
     cmGlobalGenerator* gg = status.GetMakefile().GetGlobalGenerator();
     if (cmHasLiteralPrefix(gg->GetName(), "Visual Studio 15 ")) {
       cmGlobalVisualStudioVersionedGenerator* vs15gen =
         static_cast<cmGlobalVisualStudioVersionedGenerator*>(gg);
       if (vs15gen->GetVSInstance(value)) {
-        return true;
+        return value;
       }
     }
 
@@ -120,6 +156,7 @@ bool GetValue(cmExecutionStatus& status, cmsys::SystemInformation& info,
     if (vsSetupAPIHelper.GetVSInstanceInfo(value)) {
       cmSystemTools::ConvertToUnixSlashes(value);
     }
+    return value;
   } else if (key == "VS_16_DIR") {
     // If generating for the VS 16 IDE, use the same instance.
     cmGlobalGenerator* gg = status.GetMakefile().GetGlobalGenerator();
@@ -127,7 +164,7 @@ bool GetValue(cmExecutionStatus& status, cmsys::SystemInformation& info,
       cmGlobalVisualStudioVersionedGenerator* vs16gen =
         static_cast<cmGlobalVisualStudioVersionedGenerator*>(gg);
       if (vs16gen->GetVSInstance(value)) {
-        return true;
+        return value;
       }
     }
 
@@ -136,6 +173,7 @@ bool GetValue(cmExecutionStatus& status, cmsys::SystemInformation& info,
     if (vsSetupAPIHelper.GetVSInstanceInfo(value)) {
       cmSystemTools::ConvertToUnixSlashes(value);
     }
+    return value;
   } else if (key == "VS_17_DIR") {
     // If generating for the VS 17 IDE, use the same instance.
     cmGlobalGenerator* gg = status.GetMakefile().GetGlobalGenerator();
@@ -143,7 +181,7 @@ bool GetValue(cmExecutionStatus& status, cmsys::SystemInformation& info,
       cmGlobalVisualStudioVersionedGenerator* vs17gen =
         static_cast<cmGlobalVisualStudioVersionedGenerator*>(gg);
       if (vs17gen->GetVSInstance(value)) {
-        return true;
+        return value;
       }
     }
 
@@ -152,15 +190,12 @@ bool GetValue(cmExecutionStatus& status, cmsys::SystemInformation& info,
     if (vsSetupAPIHelper.GetVSInstanceInfo(value)) {
       cmSystemTools::ConvertToUnixSlashes(value);
     }
-#endif
-  } else {
-    std::string e = "does not recognize <key> " + key;
-    status.SetError(e);
-    return false;
+    return value;
   }
 
-  return true;
+  return {};
 }
+#endif
 // END Private functions
 } // anonymous namespace
 
@@ -175,7 +210,7 @@ bool cmCMakeHostSystemInformationCommand(std::vector<std::string> const& args,
     return false;
   }
 
-  std::string const& variable = args[current_index + 1];
+  auto const& variable = args[current_index + 1];
   current_index += 2;
 
   if (args.size() < (current_index + 2) || args[current_index] != "QUERY") {
@@ -194,15 +229,24 @@ bool cmCMakeHostSystemInformationCommand(std::vector<std::string> const& args,
 
   std::string result_list;
   for (auto i = current_index + 1; i < args.size(); ++i) {
-    std::string const& key = args[i];
+    auto const& key = args[i];
     if (i != current_index + 1) {
       result_list += ";";
     }
-    std::string value;
-    if (!GetValue(status, info, key, value)) {
+    auto value = GetValue(info, key);
+    if (!value) {
+#ifdef HAVE_VS_SETUP_HELPER
+      value = GetValue(status, key);
+      if (!value) {
+        status.SetError("does not recognize <key> " + key);
+        return false;
+      }
+#else
+      status.SetError("does not recognize <key> " + key);
       return false;
+#endif
     }
-    result_list += value;
+    result_list += value.value();
   }
 
   status.GetMakefile().AddDefinition(variable, result_list);
-- 
cgit v0.12


From f9947ec9e384d12d1abc74aa5ccc8e81327580c5 Mon Sep 17 00:00:00 2001
From: Alex Turbov <i.zaufi@gmail.com>
Date: Thu, 29 Jul 2021 17:22:39 +0300
Subject: Refactor: Use string view

---
 Source/cmCMakeHostSystemInformationCommand.cxx | 60 +++++++++++++-------------
 1 file changed, 31 insertions(+), 29 deletions(-)

diff --git a/Source/cmCMakeHostSystemInformationCommand.cxx b/Source/cmCMakeHostSystemInformationCommand.cxx
index 4465a6d..2bc9816 100644
--- a/Source/cmCMakeHostSystemInformationCommand.cxx
+++ b/Source/cmCMakeHostSystemInformationCommand.cxx
@@ -5,6 +5,8 @@
 #include <cstddef>
 
 #include <cm/optional>
+#include <cm/string_view>
+#include <cmext/string_view>
 
 #include "cmsys/SystemInformation.hxx"
 
@@ -40,96 +42,96 @@ std::string ValueToString(std::string const& value)
 cm::optional<std::string> GetValue(cmsys::SystemInformation& info,
                                    std::string const& key)
 {
-  if (key == "NUMBER_OF_LOGICAL_CORES") {
+  if (key == "NUMBER_OF_LOGICAL_CORES"_s) {
     return ValueToString(info.GetNumberOfLogicalCPU());
   }
-  if (key == "NUMBER_OF_PHYSICAL_CORES") {
+  if (key == "NUMBER_OF_PHYSICAL_CORES"_s) {
     return ValueToString(info.GetNumberOfPhysicalCPU());
   }
-  if (key == "HOSTNAME") {
+  if (key == "HOSTNAME"_s) {
     return ValueToString(info.GetHostname());
   }
-  if (key == "FQDN") {
+  if (key == "FQDN"_s) {
     return ValueToString(info.GetFullyQualifiedDomainName());
   }
-  if (key == "TOTAL_VIRTUAL_MEMORY") {
+  if (key == "TOTAL_VIRTUAL_MEMORY"_s) {
     return ValueToString(info.GetTotalVirtualMemory());
   }
-  if (key == "AVAILABLE_VIRTUAL_MEMORY") {
+  if (key == "AVAILABLE_VIRTUAL_MEMORY"_s) {
     return ValueToString(info.GetAvailableVirtualMemory());
   }
-  if (key == "TOTAL_PHYSICAL_MEMORY") {
+  if (key == "TOTAL_PHYSICAL_MEMORY"_s) {
     return ValueToString(info.GetTotalPhysicalMemory());
   }
-  if (key == "AVAILABLE_PHYSICAL_MEMORY") {
+  if (key == "AVAILABLE_PHYSICAL_MEMORY"_s) {
     return ValueToString(info.GetAvailablePhysicalMemory());
   }
-  if (key == "IS_64BIT") {
+  if (key == "IS_64BIT"_s) {
     return ValueToString(info.Is64Bits());
   }
-  if (key == "HAS_FPU") {
+  if (key == "HAS_FPU"_s) {
     return ValueToString(
       info.DoesCPUSupportFeature(cmsys::SystemInformation::CPU_FEATURE_FPU));
   }
-  if (key == "HAS_MMX") {
+  if (key == "HAS_MMX"_s) {
     return ValueToString(
       info.DoesCPUSupportFeature(cmsys::SystemInformation::CPU_FEATURE_MMX));
   }
-  if (key == "HAS_MMX_PLUS") {
+  if (key == "HAS_MMX_PLUS"_s) {
     return ValueToString(info.DoesCPUSupportFeature(
       cmsys::SystemInformation::CPU_FEATURE_MMX_PLUS));
   }
-  if (key == "HAS_SSE") {
+  if (key == "HAS_SSE"_s) {
     return ValueToString(
       info.DoesCPUSupportFeature(cmsys::SystemInformation::CPU_FEATURE_SSE));
   }
-  if (key == "HAS_SSE2") {
+  if (key == "HAS_SSE2"_s) {
     return ValueToString(
       info.DoesCPUSupportFeature(cmsys::SystemInformation::CPU_FEATURE_SSE2));
   }
-  if (key == "HAS_SSE_FP") {
+  if (key == "HAS_SSE_FP"_s) {
     return ValueToString(info.DoesCPUSupportFeature(
       cmsys::SystemInformation::CPU_FEATURE_SSE_FP));
   }
-  if (key == "HAS_SSE_MMX") {
+  if (key == "HAS_SSE_MMX"_s) {
     return ValueToString(info.DoesCPUSupportFeature(
       cmsys::SystemInformation::CPU_FEATURE_SSE_MMX));
   }
-  if (key == "HAS_AMD_3DNOW") {
+  if (key == "HAS_AMD_3DNOW"_s) {
     return ValueToString(info.DoesCPUSupportFeature(
       cmsys::SystemInformation::CPU_FEATURE_AMD_3DNOW));
   }
-  if (key == "HAS_AMD_3DNOW_PLUS") {
+  if (key == "HAS_AMD_3DNOW_PLUS"_s) {
     return ValueToString(info.DoesCPUSupportFeature(
       cmsys::SystemInformation::CPU_FEATURE_AMD_3DNOW_PLUS));
   }
-  if (key == "HAS_IA64") {
+  if (key == "HAS_IA64"_s) {
     return ValueToString(
       info.DoesCPUSupportFeature(cmsys::SystemInformation::CPU_FEATURE_IA64));
   }
-  if (key == "HAS_SERIAL_NUMBER") {
+  if (key == "HAS_SERIAL_NUMBER"_s) {
     return ValueToString(info.DoesCPUSupportFeature(
       cmsys::SystemInformation::CPU_FEATURE_SERIALNUMBER));
   }
-  if (key == "PROCESSOR_NAME") {
+  if (key == "PROCESSOR_NAME"_s) {
     return ValueToString(info.GetExtendedProcessorName());
   }
-  if (key == "PROCESSOR_DESCRIPTION") {
+  if (key == "PROCESSOR_DESCRIPTION"_s) {
     return info.GetCPUDescription();
   }
-  if (key == "PROCESSOR_SERIAL_NUMBER") {
+  if (key == "PROCESSOR_SERIAL_NUMBER"_s) {
     return ValueToString(info.GetProcessorSerialNumber());
   }
-  if (key == "OS_NAME") {
+  if (key == "OS_NAME"_s) {
     return ValueToString(info.GetOSName());
   }
-  if (key == "OS_RELEASE") {
+  if (key == "OS_RELEASE"_s) {
     return ValueToString(info.GetOSRelease());
   }
-  if (key == "OS_VERSION") {
+  if (key == "OS_VERSION"_s) {
     return ValueToString(info.GetOSVersion());
   }
-  if (key == "OS_PLATFORM") {
+  if (key == "OS_PLATFORM"_s) {
     return ValueToString(info.GetOSPlatform());
   }
   return {};
@@ -205,7 +207,7 @@ bool cmCMakeHostSystemInformationCommand(std::vector<std::string> const& args,
 {
   std::size_t current_index = 0;
 
-  if (args.size() < (current_index + 2) || args[current_index] != "RESULT") {
+  if (args.size() < (current_index + 2) || args[current_index] != "RESULT"_s) {
     status.SetError("missing RESULT specification.");
     return false;
   }
@@ -213,7 +215,7 @@ bool cmCMakeHostSystemInformationCommand(std::vector<std::string> const& args,
   auto const& variable = args[current_index + 1];
   current_index += 2;
 
-  if (args.size() < (current_index + 2) || args[current_index] != "QUERY") {
+  if (args.size() < (current_index + 2) || args[current_index] != "QUERY"_s) {
     status.SetError("missing QUERY specification");
     return false;
   }
-- 
cgit v0.12


From 346f3de005722070986861450014796f84990043 Mon Sep 17 00:00:00 2001
From: Alex Turbov <i.zaufi@gmail.com>
Date: Thu, 29 Jul 2021 17:23:51 +0300
Subject: Refactor: Deduplicate code for `VS_nn_DIR` keys processing

---
 Source/cmCMakeHostSystemInformationCommand.cxx | 66 +++++++-------------------
 1 file changed, 18 insertions(+), 48 deletions(-)

diff --git a/Source/cmCMakeHostSystemInformationCommand.cxx b/Source/cmCMakeHostSystemInformationCommand.cxx
index 2bc9816..9e21208 100644
--- a/Source/cmCMakeHostSystemInformationCommand.cxx
+++ b/Source/cmCMakeHostSystemInformationCommand.cxx
@@ -17,6 +17,7 @@
 #  include "cmAlgorithms.h"
 #  include "cmGlobalGenerator.h"
 #  include "cmGlobalVisualStudioVersionedGenerator.h"
+#  include "cmStringAlgorithms.h"
 #  include "cmSystemTools.h"
 #  include "cmVSSetupHelper.h"
 #  define HAVE_VS_SETUP_HELPER
@@ -141,58 +142,27 @@ cm::optional<std::string> GetValue(cmsys::SystemInformation& info,
 cm::optional<std::string> GetValue(cmExecutionStatus& status,
                                    std::string const& key)
 {
-  std::string value;
-  if (key == "VS_15_DIR") {
-    // If generating for the VS 15 IDE, use the same instance.
-    cmGlobalGenerator* gg = status.GetMakefile().GetGlobalGenerator();
-    if (cmHasLiteralPrefix(gg->GetName(), "Visual Studio 15 ")) {
-      cmGlobalVisualStudioVersionedGenerator* vs15gen =
-        static_cast<cmGlobalVisualStudioVersionedGenerator*>(gg);
-      if (vs15gen->GetVSInstance(value)) {
-        return value;
+  auto* const gg = status.GetMakefile().GetGlobalGenerator();
+  for (auto vs : { 15, 16, 17 }) {
+    if (key == cmStrCat("VS_"_s, vs, "_DIR"_s)) {
+      std::string value;
+      // If generating for the VS nn IDE, use the same instance.
+
+      if (cmHasPrefix(gg->GetName(), cmStrCat("Visual Studio "_s, vs, ' '))) {
+        cmGlobalVisualStudioVersionedGenerator* vsNNgen =
+          static_cast<cmGlobalVisualStudioVersionedGenerator*>(gg);
+        if (vsNNgen->GetVSInstance(value)) {
+          return value;
+        }
       }
-    }
-
-    // Otherwise, find a VS 15 instance ourselves.
-    cmVSSetupAPIHelper vsSetupAPIHelper(15);
-    if (vsSetupAPIHelper.GetVSInstanceInfo(value)) {
-      cmSystemTools::ConvertToUnixSlashes(value);
-    }
-    return value;
-  } else if (key == "VS_16_DIR") {
-    // If generating for the VS 16 IDE, use the same instance.
-    cmGlobalGenerator* gg = status.GetMakefile().GetGlobalGenerator();
-    if (cmHasLiteralPrefix(gg->GetName(), "Visual Studio 16 ")) {
-      cmGlobalVisualStudioVersionedGenerator* vs16gen =
-        static_cast<cmGlobalVisualStudioVersionedGenerator*>(gg);
-      if (vs16gen->GetVSInstance(value)) {
-        return value;
-      }
-    }
 
-    // Otherwise, find a VS 16 instance ourselves.
-    cmVSSetupAPIHelper vsSetupAPIHelper(16);
-    if (vsSetupAPIHelper.GetVSInstanceInfo(value)) {
-      cmSystemTools::ConvertToUnixSlashes(value);
-    }
-    return value;
-  } else if (key == "VS_17_DIR") {
-    // If generating for the VS 17 IDE, use the same instance.
-    cmGlobalGenerator* gg = status.GetMakefile().GetGlobalGenerator();
-    if (cmHasLiteralPrefix(gg->GetName(), "Visual Studio 17 ")) {
-      cmGlobalVisualStudioVersionedGenerator* vs17gen =
-        static_cast<cmGlobalVisualStudioVersionedGenerator*>(gg);
-      if (vs17gen->GetVSInstance(value)) {
-        return value;
+      // Otherwise, find a VS nn instance ourselves.
+      cmVSSetupAPIHelper vsSetupAPIHelper(vs);
+      if (vsSetupAPIHelper.GetVSInstanceInfo(value)) {
+        cmSystemTools::ConvertToUnixSlashes(value);
       }
+      return value;
     }
-
-    // Otherwise, find a VS 17 instance ourselves.
-    cmVSSetupAPIHelper vsSetupAPIHelper(17);
-    if (vsSetupAPIHelper.GetVSInstanceInfo(value)) {
-      cmSystemTools::ConvertToUnixSlashes(value);
-    }
-    return value;
   }
 
   return {};
-- 
cgit v0.12


From 9e831284e5373002067754dfe7206e91075fa635 Mon Sep 17 00:00:00 2001
From: Alex Turbov <i.zaufi@gmail.com>
Date: Thu, 29 Jul 2021 17:40:01 +0300
Subject: Documentation: Use definition list instead of tables

Transform tables into definition list for `cmake_host_system_information`
command manual.
---
 Help/command/cmake_host_system_information.rst | 158 +++++++++++++++++++------
 1 file changed, 119 insertions(+), 39 deletions(-)

diff --git a/Help/command/cmake_host_system_information.rst b/Help/command/cmake_host_system_information.rst
index 2b902a9..ac6a008 100644
--- a/Help/command/cmake_host_system_information.rst
+++ b/Help/command/cmake_host_system_information.rst
@@ -13,45 +13,125 @@ queried.  The list of queried values is stored in ``<variable>``.
 
 ``<key>`` can be one of the following values:
 
-============================= ================================================
-Key                           Description
-============================= ================================================
-``NUMBER_OF_LOGICAL_CORES``   Number of logical cores
-``NUMBER_OF_PHYSICAL_CORES``  Number of physical cores
-``HOSTNAME``                  Hostname
-``FQDN``                      Fully qualified domain name
-``TOTAL_VIRTUAL_MEMORY``      Total virtual memory in MiB [#mebibytes]_
-``AVAILABLE_VIRTUAL_MEMORY``  Available virtual memory in MiB [#mebibytes]_
-``TOTAL_PHYSICAL_MEMORY``     Total physical memory in MiB [#mebibytes]_
-``AVAILABLE_PHYSICAL_MEMORY`` Available physical memory in MiB [#mebibytes]_
-============================= ================================================
-
-.. versionadded:: 3.10
-  Additional ``<key>`` values are available:
-
-============================= ================================================
-Key                           Description
-============================= ================================================
-``IS_64BIT``                  One if processor is 64Bit
-``HAS_FPU``                   One if processor has floating point unit
-``HAS_MMX``                   One if processor supports MMX instructions
-``HAS_MMX_PLUS``              One if processor supports Ext. MMX instructions
-``HAS_SSE``                   One if processor supports SSE instructions
-``HAS_SSE2``                  One if processor supports SSE2 instructions
-``HAS_SSE_FP``                One if processor supports SSE FP instructions
-``HAS_SSE_MMX``               One if processor supports SSE MMX instructions
-``HAS_AMD_3DNOW``             One if processor supports 3DNow instructions
-``HAS_AMD_3DNOW_PLUS``        One if processor supports 3DNow+ instructions
-``HAS_IA64``                  One if IA64 processor emulating x86
-``HAS_SERIAL_NUMBER``         One if processor has serial number
-``PROCESSOR_SERIAL_NUMBER``   Processor serial number
-``PROCESSOR_NAME``            Human readable processor name
-``PROCESSOR_DESCRIPTION``     Human readable full processor description
-``OS_NAME``                   See :variable:`CMAKE_HOST_SYSTEM_NAME`
-``OS_RELEASE``                The OS sub-type e.g. on Windows ``Professional``
-``OS_VERSION``                The OS build ID
-``OS_PLATFORM``               See :variable:`CMAKE_HOST_SYSTEM_PROCESSOR`
-============================= ================================================
+``NUMBER_OF_LOGICAL_CORES``
+  Number of logical cores
+
+``NUMBER_OF_PHYSICAL_CORES``
+  Number of physical cores
+
+``HOSTNAME``
+  Hostname
+
+``FQDN``
+  Fully qualified domain name
+
+``TOTAL_VIRTUAL_MEMORY``
+  Total virtual memory in MiB [#mebibytes]_
+
+``AVAILABLE_VIRTUAL_MEMORY``
+  Available virtual memory in MiB [#mebibytes]_
+
+``TOTAL_PHYSICAL_MEMORY``
+  Total physical memory in MiB [#mebibytes]_
+
+``AVAILABLE_PHYSICAL_MEMORY``
+  Available physical memory in MiB [#mebibytes]_
+
+``IS_64BIT``
+  .. versionadded:: 3.10
+
+  One if processor is 64Bit
+
+``HAS_FPU``
+  .. versionadded:: 3.10
+
+  One if processor has floating point unit
+
+``HAS_MMX``
+  .. versionadded:: 3.10
+
+  One if processor supports MMX instructions
+
+``HAS_MMX_PLUS``
+  .. versionadded:: 3.10
+
+  One if processor supports Ext. MMX instructions
+
+``HAS_SSE``
+  .. versionadded:: 3.10
+
+  One if processor supports SSE instructions
+
+``HAS_SSE2``
+  .. versionadded:: 3.10
+
+  One if processor supports SSE2 instructions
+
+``HAS_SSE_FP``
+  .. versionadded:: 3.10
+
+  One if processor supports SSE FP instructions
+
+``HAS_SSE_MMX``
+  .. versionadded:: 3.10
+
+  One if processor supports SSE MMX instructions
+
+``HAS_AMD_3DNOW``
+  .. versionadded:: 3.10
+
+  One if processor supports 3DNow instructions
+
+``HAS_AMD_3DNOW_PLUS``
+  .. versionadded:: 3.10
+
+  One if processor supports 3DNow+ instructions
+
+``HAS_IA64``
+  .. versionadded:: 3.10
+
+  One if IA64 processor emulating x86
+
+``HAS_SERIAL_NUMBER``
+  .. versionadded:: 3.10
+
+  One if processor has serial number
+
+``PROCESSOR_SERIAL_NUMBER``
+  .. versionadded:: 3.10
+
+  Processor serial number
+
+``PROCESSOR_NAME``
+  .. versionadded:: 3.10
+
+  Human readable processor name
+
+``PROCESSOR_DESCRIPTION``
+  .. versionadded:: 3.10
+
+  Human readable full processor description
+
+``OS_NAME``
+  .. versionadded:: 3.10
+
+  See :variable:`CMAKE_HOST_SYSTEM_NAME`
+
+``OS_RELEASE``
+  .. versionadded:: 3.10
+
+  The OS sub-type e.g. on Windows ``Professional``
+
+``OS_VERSION``
+  .. versionadded:: 3.10
+
+  The OS build ID
+
+``OS_PLATFORM``
+  .. versionadded:: 3.10
+
+  See :variable:`CMAKE_HOST_SYSTEM_PROCESSOR`
+
 
 .. rubric:: Footnotes
 
-- 
cgit v0.12


From e808cbb1dd9bf594e2f2c8ea2c0b82b9a6590d29 Mon Sep 17 00:00:00 2001
From: Alex Turbov <i.zaufi@gmail.com>
Date: Thu, 29 Jul 2021 18:12:03 +0300
Subject: Testing: Convert `cmake_host_system_information` tests into
 `RunCMake`

---
 .../CMakeHostSystemInformation-BadArg1.cmake       |  1 -
 .../CMakeHostSystemInformation-BadArg2.cmake       |  1 -
 .../CMakeHostSystemInformation-BadArg3.cmake       |  1 -
 .../CMakeHostSystemInformation-QueryList.cmake     |  5 ---
 .../CMakeHostSystemInformationTest.cmake.in        | 52 ----------------------
 Tests/CMakeTests/CMakeLists.txt                    |  1 -
 Tests/RunCMake/CMakeLists.txt                      |  1 +
 .../BadArg1-result.txt                             |  1 +
 .../BadArg1-stderr.txt                             |  4 ++
 .../cmake_host_system_information/BadArg1.cmake    |  1 +
 .../BadArg2-result.txt                             |  1 +
 .../BadArg2-stderr.txt                             |  4 ++
 .../cmake_host_system_information/BadArg2.cmake    |  1 +
 .../BadArg3-result.txt                             |  1 +
 .../BadArg3-stderr.txt                             |  4 ++
 .../cmake_host_system_information/BadArg3.cmake    |  1 +
 .../cmake_host_system_information/CMakeLists.txt   |  7 +++
 .../QueryKeys-stdout.txt                           | 27 +++++++++++
 .../cmake_host_system_information/QueryKeys.cmake  | 32 +++++++++++++
 .../QueryList-stdout.txt                           |  1 +
 .../cmake_host_system_information/QueryList.cmake  |  5 +++
 .../RunCMakeTest.cmake                             |  8 ++++
 22 files changed, 99 insertions(+), 61 deletions(-)
 delete mode 100644 Tests/CMakeTests/CMakeHostSystemInformation-BadArg1.cmake
 delete mode 100644 Tests/CMakeTests/CMakeHostSystemInformation-BadArg2.cmake
 delete mode 100644 Tests/CMakeTests/CMakeHostSystemInformation-BadArg3.cmake
 delete mode 100644 Tests/CMakeTests/CMakeHostSystemInformation-QueryList.cmake
 delete mode 100644 Tests/CMakeTests/CMakeHostSystemInformationTest.cmake.in
 create mode 100644 Tests/RunCMake/cmake_host_system_information/BadArg1-result.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/BadArg1-stderr.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/BadArg1.cmake
 create mode 100644 Tests/RunCMake/cmake_host_system_information/BadArg2-result.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/BadArg2-stderr.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/BadArg2.cmake
 create mode 100644 Tests/RunCMake/cmake_host_system_information/BadArg3-result.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/BadArg3-stderr.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/BadArg3.cmake
 create mode 100644 Tests/RunCMake/cmake_host_system_information/CMakeLists.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/QueryKeys-stdout.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/QueryKeys.cmake
 create mode 100644 Tests/RunCMake/cmake_host_system_information/QueryList-stdout.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/QueryList.cmake
 create mode 100644 Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake

diff --git a/Tests/CMakeTests/CMakeHostSystemInformation-BadArg1.cmake b/Tests/CMakeTests/CMakeHostSystemInformation-BadArg1.cmake
deleted file mode 100644
index 1655eb4..0000000
--- a/Tests/CMakeTests/CMakeHostSystemInformation-BadArg1.cmake
+++ /dev/null
@@ -1 +0,0 @@
-cmake_host_system_information(HOSTNAME)
diff --git a/Tests/CMakeTests/CMakeHostSystemInformation-BadArg2.cmake b/Tests/CMakeTests/CMakeHostSystemInformation-BadArg2.cmake
deleted file mode 100644
index 1f056d5..0000000
--- a/Tests/CMakeTests/CMakeHostSystemInformation-BadArg2.cmake
+++ /dev/null
@@ -1 +0,0 @@
-cmake_host_system_information(RESULT FQDN HOSTNAME)
diff --git a/Tests/CMakeTests/CMakeHostSystemInformation-BadArg3.cmake b/Tests/CMakeTests/CMakeHostSystemInformation-BadArg3.cmake
deleted file mode 100644
index 9c5a558..0000000
--- a/Tests/CMakeTests/CMakeHostSystemInformation-BadArg3.cmake
+++ /dev/null
@@ -1 +0,0 @@
-cmake_host_system_information(RESULT RESULT QUERY FOOBAR)
diff --git a/Tests/CMakeTests/CMakeHostSystemInformation-QueryList.cmake b/Tests/CMakeTests/CMakeHostSystemInformation-QueryList.cmake
deleted file mode 100644
index 1c3156d..0000000
--- a/Tests/CMakeTests/CMakeHostSystemInformation-QueryList.cmake
+++ /dev/null
@@ -1,5 +0,0 @@
-cmake_host_system_information(RESULT RESULT
-  QUERY NUMBER_OF_LOGICAL_CORES NUMBER_OF_PHYSICAL_CORES
-)
-
-message("[${RESULT}]")
diff --git a/Tests/CMakeTests/CMakeHostSystemInformationTest.cmake.in b/Tests/CMakeTests/CMakeHostSystemInformationTest.cmake.in
deleted file mode 100644
index a3c2b05..0000000
--- a/Tests/CMakeTests/CMakeHostSystemInformationTest.cmake.in
+++ /dev/null
@@ -1,52 +0,0 @@
-set(BadArg1-RESULT 1)
-set(BadArg1-STDERR "missing RESULT specification")
-set(BadArg2-RESULT 1)
-set(BadArg2-STDERR "missing QUERY specification")
-set(BadArg3-RESULT 1)
-set(BadArg3-STDERR "does not recognize <key> FOOBAR")
-set(QueryList-RESULT 0)
-set(QueryList-STDERR "\\[[0-9]+;[0-9]+\\]")
-
-function(try_and_print key)
-	cmake_host_system_information(RESULT RESULT QUERY ${key})
-	message(STATUS "[${key}] [${RESULT}]")
-endfunction()
-
-message("CTEST_FULL_OUTPUT (Avoid ctest truncation of output)")
-
-try_and_print(NUMBER_OF_LOGICAL_CORES)
-try_and_print(NUMBER_OF_PHYSICAL_CORES)
-try_and_print(HOSTNAME)
-try_and_print(FQDN)
-try_and_print(TOTAL_VIRTUAL_MEMORY)
-try_and_print(AVAILABLE_VIRTUAL_MEMORY)
-try_and_print(TOTAL_PHYSICAL_MEMORY)
-try_and_print(AVAILABLE_PHYSICAL_MEMORY)
-try_and_print(IS_64BIT)
-try_and_print(HAS_FPU)
-try_and_print(HAS_MMX)
-try_and_print(HAS_MMX_PLUS)
-try_and_print(HAS_SSE)
-try_and_print(HAS_SSE2)
-try_and_print(HAS_SSE_FP)
-try_and_print(HAS_SSE_MMX)
-try_and_print(HAS_AMD_3DNOW)
-try_and_print(HAS_AMD_3DNOW_PLUS)
-try_and_print(HAS_IA64)
-try_and_print(HAS_SERIAL_NUMBER)
-try_and_print(PROCESSOR_SERIAL_NUMBER)
-try_and_print(PROCESSOR_NAME)
-try_and_print(PROCESSOR_DESCRIPTION)
-try_and_print(OS_NAME)
-try_and_print(OS_RELEASE)
-try_and_print(OS_VERSION)
-try_and_print(OS_PLATFORM)
-
-include("@CMAKE_CURRENT_SOURCE_DIR@/CheckCMakeTest.cmake")
-
-check_cmake_test(CMakeHostSystemInformation
-	BadArg1
-	BadArg2
-	BadArg3
-	QueryList
-)
diff --git a/Tests/CMakeTests/CMakeLists.txt b/Tests/CMakeTests/CMakeLists.txt
index 52959e6..9e0b891 100644
--- a/Tests/CMakeTests/CMakeLists.txt
+++ b/Tests/CMakeTests/CMakeLists.txt
@@ -31,7 +31,6 @@ AddCMakeTest(CompilerIdVendor "")
 AddCMakeTest(ProcessorCount "-DKWSYS_TEST_EXE=$<TARGET_FILE:cmsysTestsCxx>")
 AddCMakeTest(PushCheckState "")
 AddCMakeTest(While "")
-AddCMakeTest(CMakeHostSystemInformation "")
 
 AddCMakeTest(FileDownload "")
 set_tests_properties(CMake.FileDownload PROPERTIES
diff --git a/Tests/RunCMake/CMakeLists.txt b/Tests/RunCMake/CMakeLists.txt
index ef797f7..eb2c2d9 100644
--- a/Tests/RunCMake/CMakeLists.txt
+++ b/Tests/RunCMake/CMakeLists.txt
@@ -349,6 +349,7 @@ if(NOT CMake_TEST_EXTERNAL_CMAKE)
 endif()
 add_RunCMake_test(execute_process)
 add_RunCMake_test(export)
+add_RunCMake_test(cmake_host_system_information)
 add_RunCMake_test(cmake_language)
 add_RunCMake_test(cmake_minimum_required)
 add_RunCMake_test(cmake_parse_arguments)
diff --git a/Tests/RunCMake/cmake_host_system_information/BadArg1-result.txt b/Tests/RunCMake/cmake_host_system_information/BadArg1-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/BadArg1-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/cmake_host_system_information/BadArg1-stderr.txt b/Tests/RunCMake/cmake_host_system_information/BadArg1-stderr.txt
new file mode 100644
index 0000000..ed995e6
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/BadArg1-stderr.txt
@@ -0,0 +1,4 @@
+CMake Error at BadArg1\.cmake:1 \(cmake_host_system_information\):
+  cmake_host_system_information missing RESULT specification.
+Call Stack \(most recent call first\):
+  CMakeLists\.txt:7 \(include\)
diff --git a/Tests/RunCMake/cmake_host_system_information/BadArg1.cmake b/Tests/RunCMake/cmake_host_system_information/BadArg1.cmake
new file mode 100644
index 0000000..1655eb4
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/BadArg1.cmake
@@ -0,0 +1 @@
+cmake_host_system_information(HOSTNAME)
diff --git a/Tests/RunCMake/cmake_host_system_information/BadArg2-result.txt b/Tests/RunCMake/cmake_host_system_information/BadArg2-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/BadArg2-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/cmake_host_system_information/BadArg2-stderr.txt b/Tests/RunCMake/cmake_host_system_information/BadArg2-stderr.txt
new file mode 100644
index 0000000..b78c927
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/BadArg2-stderr.txt
@@ -0,0 +1,4 @@
+CMake Error at BadArg2\.cmake:1 \(cmake_host_system_information\):
+  cmake_host_system_information missing QUERY specification
+Call Stack \(most recent call first\):
+  CMakeLists\.txt:7 \(include\)
diff --git a/Tests/RunCMake/cmake_host_system_information/BadArg2.cmake b/Tests/RunCMake/cmake_host_system_information/BadArg2.cmake
new file mode 100644
index 0000000..1f056d5
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/BadArg2.cmake
@@ -0,0 +1 @@
+cmake_host_system_information(RESULT FQDN HOSTNAME)
diff --git a/Tests/RunCMake/cmake_host_system_information/BadArg3-result.txt b/Tests/RunCMake/cmake_host_system_information/BadArg3-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/BadArg3-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/cmake_host_system_information/BadArg3-stderr.txt b/Tests/RunCMake/cmake_host_system_information/BadArg3-stderr.txt
new file mode 100644
index 0000000..c3f1314
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/BadArg3-stderr.txt
@@ -0,0 +1,4 @@
+CMake Error at BadArg3\.cmake:1 \(cmake_host_system_information\):
+  cmake_host_system_information does not recognize <key> FOOBAR
+Call Stack \(most recent call first\):
+  CMakeLists\.txt:7 \(include\)
diff --git a/Tests/RunCMake/cmake_host_system_information/BadArg3.cmake b/Tests/RunCMake/cmake_host_system_information/BadArg3.cmake
new file mode 100644
index 0000000..9c5a558
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/BadArg3.cmake
@@ -0,0 +1 @@
+cmake_host_system_information(RESULT RESULT QUERY FOOBAR)
diff --git a/Tests/RunCMake/cmake_host_system_information/CMakeLists.txt b/Tests/RunCMake/cmake_host_system_information/CMakeLists.txt
new file mode 100644
index 0000000..0198f9b
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/CMakeLists.txt
@@ -0,0 +1,7 @@
+cmake_minimum_required(VERSION 3.21)
+
+project(${RunCMake_TEST} NONE)
+
+set(CMAKE_SYSROOT ${PROJECT_SOURCE_DIR}/${RunCMake_TEST})
+
+include(${RunCMake_TEST}.cmake)
diff --git a/Tests/RunCMake/cmake_host_system_information/QueryKeys-stdout.txt b/Tests/RunCMake/cmake_host_system_information/QueryKeys-stdout.txt
new file mode 100644
index 0000000..f583deb
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/QueryKeys-stdout.txt
@@ -0,0 +1,27 @@
+-- NUMBER_OF_LOGICAL_CORES=`[0-9]+`
+-- NUMBER_OF_PHYSICAL_CORES=`[0-9]+`
+-- HOSTNAME=`.*`
+-- FQDN=`.*`
+-- TOTAL_VIRTUAL_MEMORY=`[0-9]+`
+-- AVAILABLE_VIRTUAL_MEMORY=`[0-9]+`
+-- TOTAL_PHYSICAL_MEMORY=`[0-9]+`
+-- AVAILABLE_PHYSICAL_MEMORY=`[0-9]+`
+-- IS_64BIT=`[01]`
+-- HAS_FPU=`[01]`
+-- HAS_MMX=`[01]`
+-- HAS_MMX_PLUS=`[01]`
+-- HAS_SSE=`[01]`
+-- HAS_SSE2=`[01]`
+-- HAS_SSE_FP=`[01]`
+-- HAS_SSE_MMX=`[01]`
+-- HAS_AMD_3DNOW=`[01]`
+-- HAS_AMD_3DNOW_PLUS=`[01]`
+-- HAS_IA64=`[01]`
+-- HAS_SERIAL_NUMBER=`[01]`
+-- PROCESSOR_SERIAL_NUMBER=`.*`
+-- PROCESSOR_NAME=`.*`
+-- PROCESSOR_DESCRIPTION=`.*`
+-- OS_NAME=`.*`
+-- OS_RELEASE=`.*`
+-- OS_VERSION=`.*`
+-- OS_PLATFORM=`.*`
diff --git a/Tests/RunCMake/cmake_host_system_information/QueryKeys.cmake b/Tests/RunCMake/cmake_host_system_information/QueryKeys.cmake
new file mode 100644
index 0000000..f22a0ae
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/QueryKeys.cmake
@@ -0,0 +1,32 @@
+function(try_and_print key)
+  cmake_host_system_information(RESULT RESULT QUERY ${key})
+  message(STATUS "${key}=`${RESULT}`")
+endfunction()
+
+try_and_print(NUMBER_OF_LOGICAL_CORES)
+try_and_print(NUMBER_OF_PHYSICAL_CORES)
+try_and_print(HOSTNAME)
+try_and_print(FQDN)
+try_and_print(TOTAL_VIRTUAL_MEMORY)
+try_and_print(AVAILABLE_VIRTUAL_MEMORY)
+try_and_print(TOTAL_PHYSICAL_MEMORY)
+try_and_print(AVAILABLE_PHYSICAL_MEMORY)
+try_and_print(IS_64BIT)
+try_and_print(HAS_FPU)
+try_and_print(HAS_MMX)
+try_and_print(HAS_MMX_PLUS)
+try_and_print(HAS_SSE)
+try_and_print(HAS_SSE2)
+try_and_print(HAS_SSE_FP)
+try_and_print(HAS_SSE_MMX)
+try_and_print(HAS_AMD_3DNOW)
+try_and_print(HAS_AMD_3DNOW_PLUS)
+try_and_print(HAS_IA64)
+try_and_print(HAS_SERIAL_NUMBER)
+try_and_print(PROCESSOR_SERIAL_NUMBER)
+try_and_print(PROCESSOR_NAME)
+try_and_print(PROCESSOR_DESCRIPTION)
+try_and_print(OS_NAME)
+try_and_print(OS_RELEASE)
+try_and_print(OS_VERSION)
+try_and_print(OS_PLATFORM)
diff --git a/Tests/RunCMake/cmake_host_system_information/QueryList-stdout.txt b/Tests/RunCMake/cmake_host_system_information/QueryList-stdout.txt
new file mode 100644
index 0000000..eebe0d4
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/QueryList-stdout.txt
@@ -0,0 +1 @@
+-- \[[0-9]+;[0-9]+\]
diff --git a/Tests/RunCMake/cmake_host_system_information/QueryList.cmake b/Tests/RunCMake/cmake_host_system_information/QueryList.cmake
new file mode 100644
index 0000000..f24aa2b
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/QueryList.cmake
@@ -0,0 +1,5 @@
+cmake_host_system_information(RESULT RESULT
+  QUERY NUMBER_OF_LOGICAL_CORES NUMBER_OF_PHYSICAL_CORES
+)
+
+message(STATUS "[${RESULT}]")
diff --git a/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake b/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake
new file mode 100644
index 0000000..be74ade
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake
@@ -0,0 +1,8 @@
+include(RunCMake)
+
+run_cmake(BadArg1)
+run_cmake(BadArg2)
+run_cmake(BadArg3)
+
+run_cmake(QueryList)
+run_cmake(QueryKeys)
-- 
cgit v0.12


From 1e65e4a6e5c4870960b998b6f5d6f70965cc9344 Mon Sep 17 00:00:00 2001
From: Alex Turbov <i.zaufi@gmail.com>
Date: Fri, 30 Jul 2021 03:49:04 +0300
Subject: cmake_host_system_information: Can read `/etc/os-release` file

---
 Help/command/cmake_host_system_information.rst     |  45 +++++
 Help/release/dev/os-release.rst                    |   6 +
 Source/cmCMakeHostSystemInformationCommand.cxx     | 197 ++++++++++++++++++++-
 Tests/RunCMake/CMakeLists.txt                      |   2 +-
 .../Exherbo-stdout.txt                             |   9 +
 .../cmake_host_system_information/Exherbo.cmake    |  11 ++
 .../Exherbo/etc/os-release                         |   7 +
 .../RunCMakeTest.cmake                             |   8 +
 .../Ubuntu-stdout.txt                              |  14 ++
 .../cmake_host_system_information/Ubuntu.cmake     |  11 ++
 .../Ubuntu/etc/os-release                          |  12 ++
 .../UnitTest-stdout.txt                            |   7 +
 .../cmake_host_system_information/UnitTest.cmake   |   5 +
 .../UnitTest/etc/os-release                        |   9 +
 14 files changed, 336 insertions(+), 7 deletions(-)
 create mode 100644 Help/release/dev/os-release.rst
 create mode 100644 Tests/RunCMake/cmake_host_system_information/Exherbo-stdout.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/Exherbo.cmake
 create mode 100644 Tests/RunCMake/cmake_host_system_information/Exherbo/etc/os-release
 create mode 100644 Tests/RunCMake/cmake_host_system_information/Ubuntu-stdout.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/Ubuntu.cmake
 create mode 100644 Tests/RunCMake/cmake_host_system_information/Ubuntu/etc/os-release
 create mode 100644 Tests/RunCMake/cmake_host_system_information/UnitTest-stdout.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/UnitTest.cmake
 create mode 100644 Tests/RunCMake/cmake_host_system_information/UnitTest/etc/os-release

diff --git a/Help/command/cmake_host_system_information.rst b/Help/command/cmake_host_system_information.rst
index ac6a008..ae24b03 100644
--- a/Help/command/cmake_host_system_information.rst
+++ b/Help/command/cmake_host_system_information.rst
@@ -132,7 +132,52 @@ queried.  The list of queried values is stored in ``<variable>``.
 
   See :variable:`CMAKE_HOST_SYSTEM_PROCESSOR`
 
+For Linux distributions additional ``<key>`` values are available to get operating
+system identification as described in the `man 5 os-release`_.
+
+``DISTRIB_INFO``
+  .. versionadded:: 3.22
+
+  Read :file:`/etc/os-release` file and define the given ``<variable>``
+  into a list of read variables
+
+``DISTRIB_<name>``
+  .. versionadded:: 3.22
+
+  Get the ``<name>`` variable if it exists in the :file:`/etc/os-release` file
+
+  Example:
+
+  .. code-block:: cmake
+
+      cmake_host_system_information(RESULT PRETTY_NAME QUERY DISTRIB_PRETTY_NAME)
+      message(STATUS "${PRETTY_NAME}")
+
+      cmake_host_system_information(RESULT DISTRO QUERY DISTRIB_INFO)
+
+      foreach(VAR IN LISTS DISTRO)
+        message(STATUS "${VAR}=`${${VAR}}`")
+      endforeach()
+
+
+  Output::
+
+    -- Ubuntu 20.04.2 LTS
+    -- DISTRO_BUG_REPORT_URL=`https://bugs.launchpad.net/ubuntu/`
+    -- DISTRO_HOME_URL=`https://www.ubuntu.com/`
+    -- DISTRO_ID=`ubuntu`
+    -- DISTRO_ID_LIKE=`debian`
+    -- DISTRO_NAME=`Ubuntu`
+    -- DISTRO_PRETTY_NAME=`Ubuntu 20.04.2 LTS`
+    -- DISTRO_PRIVACY_POLICY_URL=`https://www.ubuntu.com/legal/terms-and-policies/privacy-policy`
+    -- DISTRO_SUPPORT_URL=`https://help.ubuntu.com/`
+    -- DISTRO_UBUNTU_CODENAME=`focal`
+    -- DISTRO_VERSION=`20.04.2 LTS (Focal Fossa)`
+    -- DISTRO_VERSION_CODENAME=`focal`
+    -- DISTRO_VERSION_ID=`20.04`
 
 .. rubric:: Footnotes
 
 .. [#mebibytes] One MiB (mebibyte) is equal to 1024x1024 bytes.
+
+.. _man 5 os-release: https://www.freedesktop.org/software/systemd/man/os-release.html
diff --git a/Help/release/dev/os-release.rst b/Help/release/dev/os-release.rst
new file mode 100644
index 0000000..cce6aee
--- /dev/null
+++ b/Help/release/dev/os-release.rst
@@ -0,0 +1,6 @@
+os-release
+----------
+
+* The :command:`cmake_host_system_information` command query operating system
+  identification `variables <https://www.freedesktop.org/software/systemd/man/os-release.html>`_
+  from the :file:`/etc/os-release` file.
diff --git a/Source/cmCMakeHostSystemInformationCommand.cxx b/Source/cmCMakeHostSystemInformationCommand.cxx
index 9e21208..cdd6b4c 100644
--- a/Source/cmCMakeHostSystemInformationCommand.cxx
+++ b/Source/cmCMakeHostSystemInformationCommand.cxx
@@ -2,28 +2,37 @@
    file Copyright.txt or https://cmake.org/licensing for details.  */
 #include "cmCMakeHostSystemInformationCommand.h"
 
-#include <cstddef>
+#include <cassert>
+#include <cctype>
+#include <initializer_list>
+#include <map>
+#include <string>
+#include <type_traits>
+#include <utility>
 
 #include <cm/optional>
 #include <cm/string_view>
 #include <cmext/string_view>
 
+#include "cmsys/FStream.hxx"
 #include "cmsys/SystemInformation.hxx"
 
 #include "cmExecutionStatus.h"
 #include "cmMakefile.h"
+#include "cmStringAlgorithms.h"
+#include "cmSystemTools.h"
 
 #ifdef _WIN32
 #  include "cmAlgorithms.h"
 #  include "cmGlobalGenerator.h"
 #  include "cmGlobalVisualStudioVersionedGenerator.h"
-#  include "cmStringAlgorithms.h"
-#  include "cmSystemTools.h"
 #  include "cmVSSetupHelper.h"
 #  define HAVE_VS_SETUP_HELPER
 #endif
 
 namespace {
+std::string const DELIM[2] = { {}, ";" };
+
 // BEGIN Private functions
 std::string ValueToString(std::size_t const value)
 {
@@ -138,6 +147,177 @@ cm::optional<std::string> GetValue(cmsys::SystemInformation& info,
   return {};
 }
 
+#ifdef __linux__
+cm::optional<std::pair<std::string, std::string>> ParseOSReleaseLine(
+  std::string const& line)
+{
+  std::string key;
+  std::string value;
+
+  char prev = 0;
+  enum ParserState
+  {
+    PARSE_KEY_1ST,
+    PARSE_KEY,
+    FOUND_EQ,
+    PARSE_SINGLE_QUOTE_VALUE,
+    PARSE_DBL_QUOTE_VALUE,
+    PARSE_VALUE,
+    IGNORE_REST
+  } state = PARSE_KEY_1ST;
+
+  for (auto ch : line) {
+    switch (state) {
+      case PARSE_KEY_1ST:
+        if (std::isalpha(ch) || ch == '_') {
+          key += ch;
+          state = PARSE_KEY;
+        } else if (!std::isspace(ch)) {
+          state = IGNORE_REST;
+        }
+        break;
+
+      case PARSE_KEY:
+        if (ch == '=') {
+          state = FOUND_EQ;
+        } else if (std::isalnum(ch) || ch == '_') {
+          key += ch;
+        } else {
+          state = IGNORE_REST;
+        }
+        break;
+
+      case FOUND_EQ:
+        switch (ch) {
+          case '\'':
+            state = PARSE_SINGLE_QUOTE_VALUE;
+            break;
+          case '"':
+            state = PARSE_DBL_QUOTE_VALUE;
+            break;
+          case '#':
+          case '\\':
+            state = IGNORE_REST;
+            break;
+          default:
+            value += ch;
+            state = PARSE_VALUE;
+        }
+        break;
+
+      case PARSE_SINGLE_QUOTE_VALUE:
+        if (ch == '\'') {
+          if (prev != '\\') {
+            state = IGNORE_REST;
+          } else {
+            assert(!value.empty());
+            value[value.size() - 1] = ch;
+          }
+        } else {
+          value += ch;
+        }
+        break;
+
+      case PARSE_DBL_QUOTE_VALUE:
+        if (ch == '"') {
+          if (prev != '\\') {
+            state = IGNORE_REST;
+          } else {
+            assert(!value.empty());
+            value[value.size() - 1] = ch;
+          }
+        } else {
+          value += ch;
+        }
+        break;
+
+      case PARSE_VALUE:
+        if (ch == '#' || std::isspace(ch)) {
+          state = IGNORE_REST;
+        } else {
+          value += ch;
+        }
+        break;
+
+      default:
+        // Unexpected os-release parser state!
+        state = IGNORE_REST;
+        break;
+    }
+
+    if (state == IGNORE_REST) {
+      break;
+    }
+    prev = ch;
+  }
+  if (!(key.empty() || value.empty())) {
+    return std::make_pair(key, value);
+  }
+  return {};
+}
+
+std::map<std::string, std::string> GetOSReleaseVariables(
+  cmExecutionStatus& status)
+{
+  const auto& sysroot =
+    status.GetMakefile().GetSafeDefinition("CMAKE_SYSROOT");
+
+  std::map<std::string, std::string> data;
+  // Based on
+  // https://www.freedesktop.org/software/systemd/man/os-release.html
+  for (auto name : { "/etc/os-release"_s, "/usr/lib/os-release"_s }) {
+    const auto& filename = cmStrCat(sysroot, name);
+    if (cmSystemTools::FileExists(filename)) {
+      cmsys::ifstream fin(filename.c_str());
+      for (std::string line; !std::getline(fin, line).fail();) {
+        auto kv = ParseOSReleaseLine(line);
+        if (kv.has_value()) {
+          data.emplace(kv.value());
+        }
+      }
+      break;
+    }
+  }
+  return data;
+}
+
+cm::optional<std::string> GetValue(cmExecutionStatus& status,
+                                   std::string const& key,
+                                   std::string const& variable)
+{
+  const auto prefix = "DISTRIB_"_s;
+  if (!cmHasPrefix(key, prefix)) {
+    return {};
+  }
+
+  static const std::map<std::string, std::string> s_os_release =
+    GetOSReleaseVariables(status);
+
+  auto& makefile = status.GetMakefile();
+
+  const std::string subkey =
+    key.substr(prefix.size(), key.size() - prefix.size());
+  if (subkey == "INFO"_s) {
+    std::string vars;
+    for (const auto& kv : s_os_release) {
+      auto cmake_var_name = cmStrCat(variable, '_', kv.first);
+      vars += DELIM[!vars.empty()] + cmake_var_name;
+      makefile.AddDefinition(cmake_var_name, kv.second);
+    }
+    return cm::optional<std::string>(std::move(vars));
+  }
+
+  // Query individual variable
+  const auto it = s_os_release.find(subkey);
+  if (it != s_os_release.cend()) {
+    return it->second;
+  }
+
+  // NOTE Empty string means requested variable not set
+  return std::string{};
+}
+#endif
+
 #ifdef HAVE_VS_SETUP_HELPER
 cm::optional<std::string> GetValue(cmExecutionStatus& status,
                                    std::string const& key)
@@ -201,10 +381,9 @@ bool cmCMakeHostSystemInformationCommand(std::vector<std::string> const& args,
 
   std::string result_list;
   for (auto i = current_index + 1; i < args.size(); ++i) {
+    result_list += DELIM[!result_list.empty()];
+
     auto const& key = args[i];
-    if (i != current_index + 1) {
-      result_list += ";";
-    }
     auto value = GetValue(info, key);
     if (!value) {
 #ifdef HAVE_VS_SETUP_HELPER
@@ -213,6 +392,12 @@ bool cmCMakeHostSystemInformationCommand(std::vector<std::string> const& args,
         status.SetError("does not recognize <key> " + key);
         return false;
       }
+#elif defined(__linux__)
+      value = GetValue(status, key, variable);
+      if (!value) {
+        status.SetError("does not recognize <key> " + key);
+        return false;
+      }
 #else
       status.SetError("does not recognize <key> " + key);
       return false;
diff --git a/Tests/RunCMake/CMakeLists.txt b/Tests/RunCMake/CMakeLists.txt
index eb2c2d9..543ad1d 100644
--- a/Tests/RunCMake/CMakeLists.txt
+++ b/Tests/RunCMake/CMakeLists.txt
@@ -349,7 +349,7 @@ if(NOT CMake_TEST_EXTERNAL_CMAKE)
 endif()
 add_RunCMake_test(execute_process)
 add_RunCMake_test(export)
-add_RunCMake_test(cmake_host_system_information)
+add_RunCMake_test(cmake_host_system_information -DCMAKE_SYSTEM_NAME=${CMAKE_SYSTEM_NAME})
 add_RunCMake_test(cmake_language)
 add_RunCMake_test(cmake_minimum_required)
 add_RunCMake_test(cmake_parse_arguments)
diff --git a/Tests/RunCMake/cmake_host_system_information/Exherbo-stdout.txt b/Tests/RunCMake/cmake_host_system_information/Exherbo-stdout.txt
new file mode 100644
index 0000000..11ae71f
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/Exherbo-stdout.txt
@@ -0,0 +1,9 @@
+-- TEST1_ANSI_COLOR=`0;32`
+-- TEST1_BUG_REPORT_URL=`https://bugs.exherbo.org/`
+-- TEST1_HOME_URL=`https://www.exherbo.org/`
+-- TEST1_ID=`exherbo`
+-- TEST1_NAME=`Exherbo`
+-- TEST1_PRETTY_NAME=`Exherbo Linux`
+-- TEST1_SUPPORT_URL=`irc://irc.freenode.net/#exherbo`
+-- TEST2_ID=`exherbo`
+-- TEST2_VERSION=``
diff --git a/Tests/RunCMake/cmake_host_system_information/Exherbo.cmake b/Tests/RunCMake/cmake_host_system_information/Exherbo.cmake
new file mode 100644
index 0000000..7fc26d8
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/Exherbo.cmake
@@ -0,0 +1,11 @@
+cmake_host_system_information(RESULT TEST1 QUERY DISTRIB_INFO)
+
+foreach(VAR IN LISTS TEST1)
+  message(STATUS "${VAR}=`${${VAR}}`")
+endforeach()
+
+# Query individual variables
+cmake_host_system_information(RESULT TEST2 QUERY DISTRIB_ID DISTRIB_VERSION)
+list(POP_FRONT TEST2 TEST2_ID TEST2_VERSION)
+message(STATUS "TEST2_ID=`${TEST2_ID}`")
+message(STATUS "TEST2_VERSION=`${TEST2_VERSION}`")
diff --git a/Tests/RunCMake/cmake_host_system_information/Exherbo/etc/os-release b/Tests/RunCMake/cmake_host_system_information/Exherbo/etc/os-release
new file mode 100644
index 0000000..944c9b4
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/Exherbo/etc/os-release
@@ -0,0 +1,7 @@
+NAME="Exherbo"
+PRETTY_NAME="Exherbo Linux"
+ID="exherbo"
+ANSI_COLOR="0;32"
+HOME_URL="https://www.exherbo.org/"
+SUPPORT_URL="irc://irc.freenode.net/#exherbo"
+BUG_REPORT_URL="https://bugs.exherbo.org/"
diff --git a/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake b/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake
index be74ade..6cbb7fd 100644
--- a/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake
+++ b/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake
@@ -6,3 +6,11 @@ run_cmake(BadArg3)
 
 run_cmake(QueryList)
 run_cmake(QueryKeys)
+
+if (CMAKE_SYSTEM_NAME MATCHES "Linux")
+
+  run_cmake_with_options(UnitTest)
+  run_cmake_with_options(Exherbo)
+  run_cmake_with_options(Ubuntu)
+
+endif()
diff --git a/Tests/RunCMake/cmake_host_system_information/Ubuntu-stdout.txt b/Tests/RunCMake/cmake_host_system_information/Ubuntu-stdout.txt
new file mode 100644
index 0000000..d1a18da
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/Ubuntu-stdout.txt
@@ -0,0 +1,14 @@
+-- TEST1_BUG_REPORT_URL=`https://bugs\.launchpad\.net/ubuntu/`
+-- TEST1_HOME_URL=`https://www\.ubuntu\.com/`
+-- TEST1_ID=`ubuntu`
+-- TEST1_ID_LIKE=`debian`
+-- TEST1_NAME=`Ubuntu`
+-- TEST1_PRETTY_NAME=`Ubuntu 20\.04\.2 LTS`
+-- TEST1_PRIVACY_POLICY_URL=`https://www\.ubuntu\.com/legal/terms-and-policies/privacy-policy`
+-- TEST1_SUPPORT_URL=`https://help\.ubuntu\.com/`
+-- TEST1_UBUNTU_CODENAME=`focal`
+-- TEST1_VERSION=`20\.04\.2 LTS \(Focal Fossa\)`
+-- TEST1_VERSION_CODENAME=`focal`
+-- TEST1_VERSION_ID=`20\.04`
+-- TEST2_ID=`ubuntu`
+-- TEST2_VERSION=`20\.04\.2 LTS \(Focal Fossa\)`
diff --git a/Tests/RunCMake/cmake_host_system_information/Ubuntu.cmake b/Tests/RunCMake/cmake_host_system_information/Ubuntu.cmake
new file mode 100644
index 0000000..7fc26d8
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/Ubuntu.cmake
@@ -0,0 +1,11 @@
+cmake_host_system_information(RESULT TEST1 QUERY DISTRIB_INFO)
+
+foreach(VAR IN LISTS TEST1)
+  message(STATUS "${VAR}=`${${VAR}}`")
+endforeach()
+
+# Query individual variables
+cmake_host_system_information(RESULT TEST2 QUERY DISTRIB_ID DISTRIB_VERSION)
+list(POP_FRONT TEST2 TEST2_ID TEST2_VERSION)
+message(STATUS "TEST2_ID=`${TEST2_ID}`")
+message(STATUS "TEST2_VERSION=`${TEST2_VERSION}`")
diff --git a/Tests/RunCMake/cmake_host_system_information/Ubuntu/etc/os-release b/Tests/RunCMake/cmake_host_system_information/Ubuntu/etc/os-release
new file mode 100644
index 0000000..f228f22
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/Ubuntu/etc/os-release
@@ -0,0 +1,12 @@
+NAME="Ubuntu"
+VERSION="20.04.2 LTS (Focal Fossa)"
+ID=ubuntu
+ID_LIKE=debian
+PRETTY_NAME="Ubuntu 20.04.2 LTS"
+VERSION_ID="20.04"
+HOME_URL="https://www.ubuntu.com/"
+SUPPORT_URL="https://help.ubuntu.com/"
+BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
+PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
+VERSION_CODENAME=focal
+UBUNTU_CODENAME=focal
diff --git a/Tests/RunCMake/cmake_host_system_information/UnitTest-stdout.txt b/Tests/RunCMake/cmake_host_system_information/UnitTest-stdout.txt
new file mode 100644
index 0000000..db6f487
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/UnitTest-stdout.txt
@@ -0,0 +1,7 @@
+-- UNIT_TEST_A_LIST_LIKE_VARIABLE=`satu;dua;tiga`
+-- UNIT_TEST_DBL_QUOTED_VALUE=`"The" value in double "quotes"`
+-- UNIT_TEST_DBL_QUOTED_VALUE_STIPPED_COMMENT=`Blah blah blah`
+-- UNIT_TEST_NON_SPACE_VALUE=`Blah-blah-blah`
+-- UNIT_TEST_QUOTED_VALUE=`'The' value in single 'quotes'`
+-- UNIT_TEST_QUOTED_VALUE_STIPPED_COMMENT=`The value in single quotes`
+-- UNIT_TEST_THE_URL_WITH_ANCHOR_TEST=`https://blah.blah/resource#anchor`
diff --git a/Tests/RunCMake/cmake_host_system_information/UnitTest.cmake b/Tests/RunCMake/cmake_host_system_information/UnitTest.cmake
new file mode 100644
index 0000000..d9a0aca
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/UnitTest.cmake
@@ -0,0 +1,5 @@
+cmake_host_system_information(RESULT UNIT_TEST QUERY DISTRIB_INFO)
+
+foreach(VAR IN LISTS UNIT_TEST)
+  message(STATUS "${VAR}=`${${VAR}}`")
+endforeach()
diff --git a/Tests/RunCMake/cmake_host_system_information/UnitTest/etc/os-release b/Tests/RunCMake/cmake_host_system_information/UnitTest/etc/os-release
new file mode 100644
index 0000000..66c33b5
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/UnitTest/etc/os-release
@@ -0,0 +1,9 @@
+# Comment string gonna be ignored
+NON_SPACE_VALUE=Blah-blah-blah
+QUOTED_VALUE='\'The\' value in single \'quotes\''
+QUOTED_VALUE_STIPPED_COMMENT='The value in single quotes'# The comment right after `'`
+DBL_QUOTED_VALUE="\"The\" value in double \"quotes\""
+DBL_QUOTED_VALUE_STIPPED_COMMENT="Blah blah blah"# The comment right after `'`
+THE_URL_WITH_ANCHOR_TEST="https://blah.blah/resource#anchor" # And a comment after
+A_LIST_LIKE_VARIABLE='satu;dua;tiga'
+INCORRECT_ESCAPE_IGNORED=\'This line gonna be ignored'
-- 
cgit v0.12


From efe139d1b835d126d7280d5bf615fe8149f923e5 Mon Sep 17 00:00:00 2001
From: Alex Turbov <i.zaufi@gmail.com>
Date: Tue, 3 Aug 2021 16:49:02 +0300
Subject: cmake_host_system_information: Can run fallback scripts

---
 Help/command/cmake_host_system_information.rst     | 67 ++++++++++++++++
 Modules/Internal/OSRelease/010-TryOldCentOS.cmake  | 41 ++++++++++
 .../Internal/OSRelease/020-TryDebianVersion.cmake  | 38 +++++++++
 Source/cmCMakeHostSystemInformationCommand.cxx     | 92 +++++++++++++++++++++-
 .../000-FirstFallbackScript.cmake                  |  1 +
 .../999-LastFallbackScript.cmake                   | 21 +++++
 .../CentOS6-stdout.txt                             |  6 ++
 .../cmake_host_system_information/CentOS6.cmake    |  5 ++
 .../CentOS6/etc/centos-release                     |  1 +
 .../Debian6-stdout.txt                             |  4 +
 .../cmake_host_system_information/Debian6.cmake    |  5 ++
 .../Debian6/etc/debian_version                     |  1 +
 .../RunCMakeTest.cmake                             |  5 ++
 .../UserFallbackScript-stderr.txt                  |  5 ++
 .../UserFallbackScript-stdout.txt                  |  6 ++
 .../UserFallbackScript.cmake                       | 12 +++
 16 files changed, 308 insertions(+), 2 deletions(-)
 create mode 100644 Modules/Internal/OSRelease/010-TryOldCentOS.cmake
 create mode 100644 Modules/Internal/OSRelease/020-TryDebianVersion.cmake
 create mode 100644 Tests/RunCMake/cmake_host_system_information/000-FirstFallbackScript.cmake
 create mode 100644 Tests/RunCMake/cmake_host_system_information/999-LastFallbackScript.cmake
 create mode 100644 Tests/RunCMake/cmake_host_system_information/CentOS6-stdout.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/CentOS6.cmake
 create mode 100644 Tests/RunCMake/cmake_host_system_information/CentOS6/etc/centos-release
 create mode 100644 Tests/RunCMake/cmake_host_system_information/Debian6-stdout.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/Debian6.cmake
 create mode 100644 Tests/RunCMake/cmake_host_system_information/Debian6/etc/debian_version
 create mode 100644 Tests/RunCMake/cmake_host_system_information/UserFallbackScript-stderr.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/UserFallbackScript-stdout.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/UserFallbackScript.cmake

diff --git a/Help/command/cmake_host_system_information.rst b/Help/command/cmake_host_system_information.rst
index ae24b03..66249ad 100644
--- a/Help/command/cmake_host_system_information.rst
+++ b/Help/command/cmake_host_system_information.rst
@@ -176,8 +176,75 @@ system identification as described in the `man 5 os-release`_.
     -- DISTRO_VERSION_CODENAME=`focal`
     -- DISTRO_VERSION_ID=`20.04`
 
+If :file:`/etc/os-release` file is not found, the command tries to gather OS
+identification via fallback scripts.  The fallback script can use `various
+distribution-specific files`_ to collect OS identification data and map it
+into `man 5 os-release`_ variables.
+
+Fallback Interface Variables
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. variable:: CMAKE_GET_OS_RELEASE_FALLBACK_SCRIPTS
+
+  In addition to the scripts shipped with CMake, a user may append full
+  paths to his script(s) to the this list.  The script filename has the
+  following format: ``NNN-<name>.cmake``, where ``NNN`` is three digits
+  used to apply collected scripts in a specific order.
+
+.. variable:: CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_<varname>
+
+  Variables collected by the user provided fallback script
+  ought to be assigned to CMake variables using this naming
+  convention.  Example, the ``ID`` variable from the manual becomes
+  ``CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_ID``.
+
+.. variable:: CMAKE_GET_OS_RELEASE_FALLBACK_RESULT
+
+  The fallback script ought to store names of all assigned
+  ``CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_<varname>`` variables in this list.
+
+Example:
+
+.. code-block:: cmake
+
+  # Try to detect some old distribution
+  # See also
+  # - http://linuxmafia.com/faq/Admin/release-files.html
+  #
+  if(NOT EXISTS "${CMAKE_SYSROOT}/etc/foobar-release")
+    return()
+  endif()
+  # Get the first string only
+  file(
+      STRINGS "${CMAKE_SYSROOT}/etc/foobar-release" CMAKE_GET_OS_RELEASE_FALLBACK_CONTENT
+      LIMIT_COUNT 1
+    )
+  #
+  # Example:
+  #
+  #   Foobar distribution release 1.2.3 (server)
+  #
+  if(CMAKE_GET_OS_RELEASE_FALLBACK_CONTENT MATCHES "Foobar distribution release ([0-9\.]+) .*")
+    set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_NAME Foobar)
+    set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_PRETTY_NAME "${CMAKE_GET_OS_RELEASE_FALLBACK_CONTENT}")
+    set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_ID foobar)
+    set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION ${CMAKE_MATCH_1})
+    set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION_ID ${CMAKE_MATCH_1})
+    list(
+        APPEND CMAKE_GET_OS_RELEASE_FALLBACK_RESULT
+        CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_NAME
+        CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_PRETTY_NAME
+        CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_ID
+        CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION
+        CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION_ID
+      )
+  endif()
+  unset(CMAKE_GET_OS_RELEASE_FALLBACK_CONTENT)
+
+
 .. rubric:: Footnotes
 
 .. [#mebibytes] One MiB (mebibyte) is equal to 1024x1024 bytes.
 
 .. _man 5 os-release: https://www.freedesktop.org/software/systemd/man/os-release.html
+.. _various distribution-specific files: http://linuxmafia.com/faq/Admin/release-files.html
diff --git a/Modules/Internal/OSRelease/010-TryOldCentOS.cmake b/Modules/Internal/OSRelease/010-TryOldCentOS.cmake
new file mode 100644
index 0000000..ff35897
--- /dev/null
+++ b/Modules/Internal/OSRelease/010-TryOldCentOS.cmake
@@ -0,0 +1,41 @@
+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+# Author: Alex Turbov
+
+if(NOT EXISTS "${CMAKE_SYSROOT}/etc/centos-release")
+  return()
+endif()
+
+# Get the first string only
+file(
+    STRINGS "${CMAKE_SYSROOT}/etc/centos-release" CMAKE_GET_OS_RELEASE_FALLBACK_CONTENT
+    LIMIT_COUNT 1
+  )
+
+#
+# Example:
+#   CentOS release 6.10 (Final)
+#
+if(CMAKE_GET_OS_RELEASE_FALLBACK_CONTENT MATCHES "CentOS release ([0-9\.]+) .*")
+
+  set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_NAME CentOS)
+  set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_PRETTY_NAME "${CMAKE_GET_OS_RELEASE_FALLBACK_CONTENT}")
+  set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_ID centos)
+  set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_ID_LIKE rhel)
+  set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION ${CMAKE_MATCH_1})
+  set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION_ID ${CMAKE_MATCH_1})
+
+  list(
+      APPEND CMAKE_GET_OS_RELEASE_FALLBACK_RESULT
+      CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_NAME
+      CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_PRETTY_NAME
+      CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_ID
+      CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_ID_LIKE
+      CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION
+      CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION_ID
+    )
+
+endif()
+
+unset(CMAKE_GET_OS_RELEASE_FALLBACK_CONTENT)
diff --git a/Modules/Internal/OSRelease/020-TryDebianVersion.cmake b/Modules/Internal/OSRelease/020-TryDebianVersion.cmake
new file mode 100644
index 0000000..8ebe19a
--- /dev/null
+++ b/Modules/Internal/OSRelease/020-TryDebianVersion.cmake
@@ -0,0 +1,38 @@
+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+# Author: Alex Turbov
+
+if(NOT EXISTS "${CMAKE_SYSROOT}/etc/debian_version")
+  return()
+endif()
+
+# Get the first string only
+file(
+    STRINGS "${CMAKE_SYSROOT}/etc/debian_version" CMAKE_GET_OS_RELEASE_FALLBACK_CONTENT
+    LIMIT_COUNT 1
+  )
+
+#
+# Example:
+#   6.0.10          # Old debian
+#   wheezy/sid      # Ubuntu
+#
+if(CMAKE_GET_OS_RELEASE_FALLBACK_CONTENT MATCHES "[0-9]+(\.[0-9]+)*")
+
+  set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_NAME Debian)
+  set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_ID debian)
+  set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION ${CMAKE_GET_OS_RELEASE_FALLBACK_CONTENT})
+  set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION_ID ${CMAKE_GET_OS_RELEASE_FALLBACK_CONTENT})
+
+  list(
+      APPEND CMAKE_GET_OS_RELEASE_FALLBACK_RESULT
+      CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_NAME
+      CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_ID
+      CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION
+      CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION_ID
+    )
+
+endif()
+
+unset(CMAKE_GET_OS_RELEASE_FALLBACK_CONTENT)
diff --git a/Source/cmCMakeHostSystemInformationCommand.cxx b/Source/cmCMakeHostSystemInformationCommand.cxx
index cdd6b4c..90240a1 100644
--- a/Source/cmCMakeHostSystemInformationCommand.cxx
+++ b/Source/cmCMakeHostSystemInformationCommand.cxx
@@ -2,6 +2,7 @@
    file Copyright.txt or https://cmake.org/licensing for details.  */
 #include "cmCMakeHostSystemInformationCommand.h"
 
+#include <algorithm>
 #include <cassert>
 #include <cctype>
 #include <initializer_list>
@@ -15,6 +16,7 @@
 #include <cmext/string_view>
 
 #include "cmsys/FStream.hxx"
+#include "cmsys/Glob.hxx"
 #include "cmsys/SystemInformation.hxx"
 
 #include "cmExecutionStatus.h"
@@ -259,8 +261,8 @@ cm::optional<std::pair<std::string, std::string>> ParseOSReleaseLine(
 std::map<std::string, std::string> GetOSReleaseVariables(
   cmExecutionStatus& status)
 {
-  const auto& sysroot =
-    status.GetMakefile().GetSafeDefinition("CMAKE_SYSROOT");
+  auto& makefile = status.GetMakefile();
+  const auto& sysroot = makefile.GetSafeDefinition("CMAKE_SYSROOT");
 
   std::map<std::string, std::string> data;
   // Based on
@@ -278,6 +280,92 @@ std::map<std::string, std::string> GetOSReleaseVariables(
       break;
     }
   }
+  // Got smth?
+  if (!data.empty()) {
+    return data;
+  }
+
+  // Ugh, it could be some pre-os-release distro.
+  // Lets try some fallback getters.
+
+  // 1. CMake provided
+  cmsys::Glob gl;
+  std::vector<std::string> scripts;
+  auto const findExpr = cmStrCat(cmSystemTools::GetCMakeRoot(),
+                                 "/Modules/Internal/OSRelease/*.cmake");
+  if (gl.FindFiles(findExpr)) {
+    scripts = gl.GetFiles();
+  }
+
+  // 2. User provided (append to the CMake prvided)
+  makefile.GetDefExpandList("CMAKE_GET_OS_RELEASE_FALLBACK_SCRIPTS", scripts);
+
+  // Filter out files that are not in format `NNN-name.cmake`
+  auto checkName = [](std::string const& filepath) -> bool {
+    auto const& filename = cmSystemTools::GetFilenameName(filepath);
+    // NOTE Minimum filename length expected:
+    //   NNN-<at-least-one-char-name>.cmake  --> 11
+    return (filename.size() < 11) || !std::isdigit(filename[0]) ||
+      !std::isdigit(filename[1]) || !std::isdigit(filename[2]) ||
+      filename[3] != '-';
+  };
+  scripts.erase(std::remove_if(scripts.begin(), scripts.end(), checkName),
+                scripts.end());
+
+  // Make sure scripts are running in desired order
+  std::sort(scripts.begin(), scripts.end(),
+            [](std::string const& lhs, std::string const& rhs) -> bool {
+              long lhs_order;
+              cmStrToLong(cmSystemTools::GetFilenameName(lhs).substr(0u, 3u),
+                          &lhs_order);
+              long rhs_order;
+              cmStrToLong(cmSystemTools::GetFilenameName(rhs).substr(0u, 3u),
+                          &rhs_order);
+              return lhs_order < rhs_order;
+            });
+
+  // Name of the variable to put the results
+  auto const result_variable = "CMAKE_GET_OS_RELEASE_FALLBACK_RESULT"_s;
+
+  for (auto const& script : scripts) {
+    // Unset the result variable
+    makefile.RemoveDefinition(result_variable.data());
+
+    // include FATAL_ERROR and ERROR in the return status
+    if (!makefile.ReadListFile(script) ||
+        cmSystemTools::GetErrorOccuredFlag()) {
+      // Ok, no worries... go try the next script.
+      continue;
+    }
+
+    std::vector<std::string> variables;
+    if (!makefile.GetDefExpandList(result_variable.data(), variables)) {
+      // Heh, this script didn't found anything... go try the next one.
+      continue;
+    }
+
+    for (auto const& variable : variables) {
+      auto value = makefile.GetSafeDefinition(variable);
+      makefile.RemoveDefinition(variable);
+
+      if (!cmHasPrefix(variable, cmStrCat(result_variable, '_'))) {
+        // Ignore unknown variable set by the script
+        continue;
+      }
+
+      auto key = variable.substr(result_variable.size() + 1,
+                                 variable.size() - result_variable.size() - 1);
+      data.emplace(std::move(key), std::move(value));
+    }
+
+    if (!data.empty()) {
+      // Try 'till some script can get anything
+      break;
+    }
+  }
+
+  makefile.RemoveDefinition(result_variable.data());
+
   return data;
 }
 
diff --git a/Tests/RunCMake/cmake_host_system_information/000-FirstFallbackScript.cmake b/Tests/RunCMake/cmake_host_system_information/000-FirstFallbackScript.cmake
new file mode 100644
index 0000000..ad873eb
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/000-FirstFallbackScript.cmake
@@ -0,0 +1 @@
+message(WARNING "The warning text to match just to make sure the script get executed")
diff --git a/Tests/RunCMake/cmake_host_system_information/999-LastFallbackScript.cmake b/Tests/RunCMake/cmake_host_system_information/999-LastFallbackScript.cmake
new file mode 100644
index 0000000..08d8da8
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/999-LastFallbackScript.cmake
@@ -0,0 +1,21 @@
+if(DEFINED CMAKE_GET_OS_RELEASE_FALLBACK_RESULT)
+  message(FATAL_ERROR "The `CMAKE_GET_OS_RELEASE_FALLBACK_RESULT` expected to be unset at this moment")
+endif()
+
+set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_NAME UnitTest)
+set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_PRETTY_NAME "Just a Unit Test")
+set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_ID unittest)
+set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_ID_LIKE nothing)
+set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION 0.0.1)
+set(CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION_ID 0.0.1)
+
+list(
+    APPEND CMAKE_GET_OS_RELEASE_FALLBACK_RESULT
+    CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_NAME
+    CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_PRETTY_NAME
+    IGNORED_VARIABLE_NAME_WHICH_IS_NOT_STARTED_WITH_EXPECTED_PREFIX
+    CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_ID
+    CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_ID_LIKE
+    CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION
+    CMAKE_GET_OS_RELEASE_FALLBACK_RESULT_VERSION_ID
+  )
diff --git a/Tests/RunCMake/cmake_host_system_information/CentOS6-stdout.txt b/Tests/RunCMake/cmake_host_system_information/CentOS6-stdout.txt
new file mode 100644
index 0000000..803ee08
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/CentOS6-stdout.txt
@@ -0,0 +1,6 @@
+-- CENTOS6_ID=`centos`
+-- CENTOS6_ID_LIKE=`rhel`
+-- CENTOS6_NAME=`CentOS`
+-- CENTOS6_PRETTY_NAME=`CentOS release 6\.10 \(Final\)`
+-- CENTOS6_VERSION=`6\.10`
+-- CENTOS6_VERSION_ID=`6\.10`
diff --git a/Tests/RunCMake/cmake_host_system_information/CentOS6.cmake b/Tests/RunCMake/cmake_host_system_information/CentOS6.cmake
new file mode 100644
index 0000000..3bc632b
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/CentOS6.cmake
@@ -0,0 +1,5 @@
+cmake_host_system_information(RESULT CENTOS6 QUERY DISTRIB_INFO)
+
+foreach(VAR IN LISTS CENTOS6)
+  message(STATUS "${VAR}=`${${VAR}}`")
+endforeach()
diff --git a/Tests/RunCMake/cmake_host_system_information/CentOS6/etc/centos-release b/Tests/RunCMake/cmake_host_system_information/CentOS6/etc/centos-release
new file mode 100644
index 0000000..294ccc9
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/CentOS6/etc/centos-release
@@ -0,0 +1 @@
+CentOS release 6.10 (Final)
diff --git a/Tests/RunCMake/cmake_host_system_information/Debian6-stdout.txt b/Tests/RunCMake/cmake_host_system_information/Debian6-stdout.txt
new file mode 100644
index 0000000..60d6425
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/Debian6-stdout.txt
@@ -0,0 +1,4 @@
+-- DEBIAN6_ID=`debian`
+-- DEBIAN6_NAME=`Debian`
+-- DEBIAN6_VERSION=`6\.0\.10`
+-- DEBIAN6_VERSION_ID=`6\.0\.10`
diff --git a/Tests/RunCMake/cmake_host_system_information/Debian6.cmake b/Tests/RunCMake/cmake_host_system_information/Debian6.cmake
new file mode 100644
index 0000000..cbf83a9
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/Debian6.cmake
@@ -0,0 +1,5 @@
+cmake_host_system_information(RESULT DEBIAN6 QUERY DISTRIB_INFO)
+
+foreach(VAR IN LISTS DEBIAN6)
+  message(STATUS "${VAR}=`${${VAR}}`")
+endforeach()
diff --git a/Tests/RunCMake/cmake_host_system_information/Debian6/etc/debian_version b/Tests/RunCMake/cmake_host_system_information/Debian6/etc/debian_version
new file mode 100644
index 0000000..c7d48f0
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/Debian6/etc/debian_version
@@ -0,0 +1 @@
+6.0.10
diff --git a/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake b/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake
index 6cbb7fd..7462f7a 100644
--- a/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake
+++ b/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake
@@ -13,4 +13,9 @@ if (CMAKE_SYSTEM_NAME MATCHES "Linux")
   run_cmake_with_options(Exherbo)
   run_cmake_with_options(Ubuntu)
 
+  run_cmake_with_options(CentOS6)
+  run_cmake_with_options(Debian6)
+
+  run_cmake_with_options(UserFallbackScript)
+
 endif()
diff --git a/Tests/RunCMake/cmake_host_system_information/UserFallbackScript-stderr.txt b/Tests/RunCMake/cmake_host_system_information/UserFallbackScript-stderr.txt
new file mode 100644
index 0000000..78acea2
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/UserFallbackScript-stderr.txt
@@ -0,0 +1,5 @@
+CMake Warning at 000-FirstFallbackScript\.cmake:[0-9]+ \(message\):
+  The warning text to match just to make sure the script get executed
+Call Stack \(most recent call first\):
+  UserFallbackScript\.cmake:[0-9]+ \(cmake_host_system_information\)
+  CMakeLists\.txt:[0-9]+ \(include\)
diff --git a/Tests/RunCMake/cmake_host_system_information/UserFallbackScript-stdout.txt b/Tests/RunCMake/cmake_host_system_information/UserFallbackScript-stdout.txt
new file mode 100644
index 0000000..afcc000
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/UserFallbackScript-stdout.txt
@@ -0,0 +1,6 @@
+-- UFS_ID=`unittest`
+-- UFS_ID_LIKE=`nothing`
+-- UFS_NAME=`UnitTest`
+-- UFS_PRETTY_NAME=`Just a Unit Test`
+-- UFS_VERSION=`0\.0\.1`
+-- UFS_VERSION_ID=`0\.0\.1`
diff --git a/Tests/RunCMake/cmake_host_system_information/UserFallbackScript.cmake b/Tests/RunCMake/cmake_host_system_information/UserFallbackScript.cmake
new file mode 100644
index 0000000..660aa1c
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/UserFallbackScript.cmake
@@ -0,0 +1,12 @@
+list(
+    APPEND CMAKE_GET_OS_RELEASE_FALLBACK_SCRIPTS
+    ${CMAKE_CURRENT_SOURCE_DIR}/000-FirstFallbackScript.cmake
+    ${CMAKE_CURRENT_SOURCE_DIR}/Ignored-Script.cmake
+    ${CMAKE_CURRENT_SOURCE_DIR}/999-LastFallbackScript.cmake
+  )
+
+cmake_host_system_information(RESULT UFS QUERY DISTRIB_INFO)
+
+foreach(VAR IN LISTS UFS)
+  message(STATUS "${VAR}=`${${VAR}}`")
+endforeach()
-- 
cgit v0.12


From 6c92f80f2ecb106916534d4b88704432476b9006 Mon Sep 17 00:00:00 2001
From: Alex Turbov <i.zaufi@gmail.com>
Date: Thu, 29 Jul 2021 21:32:26 +0300
Subject: cmake_host_system_information: Also set `USED_FALLBACK_SCRIPT`

If the OS identification was obtained via fallback script.
---
 Source/cmCMakeHostSystemInformationCommand.cxx                       | 5 ++++-
 Tests/RunCMake/cmake_host_system_information/CentOS6-stdout.txt      | 1 +
 Tests/RunCMake/cmake_host_system_information/Debian6-stdout.txt      | 1 +
 .../cmake_host_system_information/UserFallbackScript-stdout.txt      | 1 +
 4 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/Source/cmCMakeHostSystemInformationCommand.cxx b/Source/cmCMakeHostSystemInformationCommand.cxx
index 90240a1..1464220 100644
--- a/Source/cmCMakeHostSystemInformationCommand.cxx
+++ b/Source/cmCMakeHostSystemInformationCommand.cxx
@@ -287,6 +287,8 @@ std::map<std::string, std::string> GetOSReleaseVariables(
 
   // Ugh, it could be some pre-os-release distro.
   // Lets try some fallback getters.
+  // See also:
+  //  - http://linuxmafia.com/faq/Admin/release-files.html
 
   // 1. CMake provided
   cmsys::Glob gl;
@@ -358,8 +360,9 @@ std::map<std::string, std::string> GetOSReleaseVariables(
       data.emplace(std::move(key), std::move(value));
     }
 
+    // Try 'till some script can get anything
     if (!data.empty()) {
-      // Try 'till some script can get anything
+      data.emplace("USED_FALLBACK_SCRIPT", script);
       break;
     }
   }
diff --git a/Tests/RunCMake/cmake_host_system_information/CentOS6-stdout.txt b/Tests/RunCMake/cmake_host_system_information/CentOS6-stdout.txt
index 803ee08..50dbb08 100644
--- a/Tests/RunCMake/cmake_host_system_information/CentOS6-stdout.txt
+++ b/Tests/RunCMake/cmake_host_system_information/CentOS6-stdout.txt
@@ -2,5 +2,6 @@
 -- CENTOS6_ID_LIKE=`rhel`
 -- CENTOS6_NAME=`CentOS`
 -- CENTOS6_PRETTY_NAME=`CentOS release 6\.10 \(Final\)`
+-- CENTOS6_USED_FALLBACK_SCRIPT=`.*/Modules/Internal/OSRelease/010-TryOldCentOS.cmake`
 -- CENTOS6_VERSION=`6\.10`
 -- CENTOS6_VERSION_ID=`6\.10`
diff --git a/Tests/RunCMake/cmake_host_system_information/Debian6-stdout.txt b/Tests/RunCMake/cmake_host_system_information/Debian6-stdout.txt
index 60d6425..4193d6f 100644
--- a/Tests/RunCMake/cmake_host_system_information/Debian6-stdout.txt
+++ b/Tests/RunCMake/cmake_host_system_information/Debian6-stdout.txt
@@ -1,4 +1,5 @@
 -- DEBIAN6_ID=`debian`
 -- DEBIAN6_NAME=`Debian`
+-- DEBIAN6_USED_FALLBACK_SCRIPT=`.*/Modules/Internal/OSRelease/020-TryDebianVersion.cmake`
 -- DEBIAN6_VERSION=`6\.0\.10`
 -- DEBIAN6_VERSION_ID=`6\.0\.10`
diff --git a/Tests/RunCMake/cmake_host_system_information/UserFallbackScript-stdout.txt b/Tests/RunCMake/cmake_host_system_information/UserFallbackScript-stdout.txt
index afcc000..acaf47e 100644
--- a/Tests/RunCMake/cmake_host_system_information/UserFallbackScript-stdout.txt
+++ b/Tests/RunCMake/cmake_host_system_information/UserFallbackScript-stdout.txt
@@ -2,5 +2,6 @@
 -- UFS_ID_LIKE=`nothing`
 -- UFS_NAME=`UnitTest`
 -- UFS_PRETTY_NAME=`Just a Unit Test`
+-- UFS_USED_FALLBACK_SCRIPT=`.*/999-LastFallbackScript\.cmake`
 -- UFS_VERSION=`0\.0\.1`
 -- UFS_VERSION_ID=`0\.0\.1`
-- 
cgit v0.12


From 5469c71a824880eb646a0003cb001c58f24f9cce Mon Sep 17 00:00:00 2001
From: Alex Turbov <i.zaufi@gmail.com>
Date: Fri, 30 Jul 2021 03:49:56 +0300
Subject: Refactor: Simplify `GetValue()` function calls

---
 Source/cmCMakeHostSystemInformationCommand.cxx | 42 +++++++++++++++++---------
 1 file changed, 27 insertions(+), 15 deletions(-)

diff --git a/Source/cmCMakeHostSystemInformationCommand.cxx b/Source/cmCMakeHostSystemInformationCommand.cxx
index 1464220..b2c4534 100644
--- a/Source/cmCMakeHostSystemInformationCommand.cxx
+++ b/Source/cmCMakeHostSystemInformationCommand.cxx
@@ -439,6 +439,21 @@ cm::optional<std::string> GetValue(cmExecutionStatus& status,
   return {};
 }
 #endif
+
+cm::optional<std::string> GetValueChained()
+{
+  return {};
+}
+
+template <typename GetterFn, typename... Next>
+cm::optional<std::string> GetValueChained(GetterFn current, Next... chain)
+{
+  auto value = current();
+  if (value.has_value()) {
+    return value;
+  }
+  return GetValueChained(chain...);
+}
 // END Private functions
 } // anonymous namespace
 
@@ -475,24 +490,21 @@ bool cmCMakeHostSystemInformationCommand(std::vector<std::string> const& args,
     result_list += DELIM[!result_list.empty()];
 
     auto const& key = args[i];
-    auto value = GetValue(info, key);
-    if (!value) {
+    // clang-format off
+    auto value =
+      GetValueChained(
+          [&]() { return GetValue(info, key); }
+#ifdef __linux__
+        , [&]() { return GetValue(status, key, variable); }
+#endif
 #ifdef HAVE_VS_SETUP_HELPER
-      value = GetValue(status, key);
-      if (!value) {
-        status.SetError("does not recognize <key> " + key);
-        return false;
-      }
-#elif defined(__linux__)
-      value = GetValue(status, key, variable);
-      if (!value) {
-        status.SetError("does not recognize <key> " + key);
-        return false;
-      }
-#else
+        , [&]() { return GetValue(status, key); }
+#endif
+        );
+    // clang-format on
+    if (!value) {
       status.SetError("does not recognize <key> " + key);
       return false;
-#endif
     }
     result_list += value.value();
   }
-- 
cgit v0.12


From b9698f89df275a33b01cfc7b4f88a510ad9d8bbe Mon Sep 17 00:00:00 2001
From: Alex Turbov <i.zaufi@gmail.com>
Date: Tue, 3 Aug 2021 20:24:59 +0300
Subject: cmake_host_system_information: Make it available for all systems

Before it was Linux only.
---
 Help/command/cmake_host_system_information.rst           |  6 ++----
 Source/cmCMakeHostSystemInformationCommand.cxx           |  4 ----
 Tests/RunCMake/CMakeLists.txt                            |  2 +-
 .../cmake_host_system_information/RunCMakeTest.cmake     | 16 ++++++----------
 4 files changed, 9 insertions(+), 19 deletions(-)

diff --git a/Help/command/cmake_host_system_information.rst b/Help/command/cmake_host_system_information.rst
index 66249ad..998e146 100644
--- a/Help/command/cmake_host_system_information.rst
+++ b/Help/command/cmake_host_system_information.rst
@@ -132,9 +132,6 @@ queried.  The list of queried values is stored in ``<variable>``.
 
   See :variable:`CMAKE_HOST_SYSTEM_PROCESSOR`
 
-For Linux distributions additional ``<key>`` values are available to get operating
-system identification as described in the `man 5 os-release`_.
-
 ``DISTRIB_INFO``
   .. versionadded:: 3.22
 
@@ -144,7 +141,8 @@ system identification as described in the `man 5 os-release`_.
 ``DISTRIB_<name>``
   .. versionadded:: 3.22
 
-  Get the ``<name>`` variable if it exists in the :file:`/etc/os-release` file
+  Get the ``<name>`` variable (see `man 5 os-release`_) if it exists in the
+  :file:`/etc/os-release` file
 
   Example:
 
diff --git a/Source/cmCMakeHostSystemInformationCommand.cxx b/Source/cmCMakeHostSystemInformationCommand.cxx
index b2c4534..74071ff 100644
--- a/Source/cmCMakeHostSystemInformationCommand.cxx
+++ b/Source/cmCMakeHostSystemInformationCommand.cxx
@@ -149,7 +149,6 @@ cm::optional<std::string> GetValue(cmsys::SystemInformation& info,
   return {};
 }
 
-#ifdef __linux__
 cm::optional<std::pair<std::string, std::string>> ParseOSReleaseLine(
   std::string const& line)
 {
@@ -407,7 +406,6 @@ cm::optional<std::string> GetValue(cmExecutionStatus& status,
   // NOTE Empty string means requested variable not set
   return std::string{};
 }
-#endif
 
 #ifdef HAVE_VS_SETUP_HELPER
 cm::optional<std::string> GetValue(cmExecutionStatus& status,
@@ -494,9 +492,7 @@ bool cmCMakeHostSystemInformationCommand(std::vector<std::string> const& args,
     auto value =
       GetValueChained(
           [&]() { return GetValue(info, key); }
-#ifdef __linux__
         , [&]() { return GetValue(status, key, variable); }
-#endif
 #ifdef HAVE_VS_SETUP_HELPER
         , [&]() { return GetValue(status, key); }
 #endif
diff --git a/Tests/RunCMake/CMakeLists.txt b/Tests/RunCMake/CMakeLists.txt
index 543ad1d..eb2c2d9 100644
--- a/Tests/RunCMake/CMakeLists.txt
+++ b/Tests/RunCMake/CMakeLists.txt
@@ -349,7 +349,7 @@ if(NOT CMake_TEST_EXTERNAL_CMAKE)
 endif()
 add_RunCMake_test(execute_process)
 add_RunCMake_test(export)
-add_RunCMake_test(cmake_host_system_information -DCMAKE_SYSTEM_NAME=${CMAKE_SYSTEM_NAME})
+add_RunCMake_test(cmake_host_system_information)
 add_RunCMake_test(cmake_language)
 add_RunCMake_test(cmake_minimum_required)
 add_RunCMake_test(cmake_parse_arguments)
diff --git a/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake b/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake
index 7462f7a..189013f 100644
--- a/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake
+++ b/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake
@@ -7,15 +7,11 @@ run_cmake(BadArg3)
 run_cmake(QueryList)
 run_cmake(QueryKeys)
 
-if (CMAKE_SYSTEM_NAME MATCHES "Linux")
+run_cmake(UnitTest)
+run_cmake(Exherbo)
+run_cmake(Ubuntu)
 
-  run_cmake_with_options(UnitTest)
-  run_cmake_with_options(Exherbo)
-  run_cmake_with_options(Ubuntu)
+run_cmake(CentOS6)
+run_cmake(Debian6)
 
-  run_cmake_with_options(CentOS6)
-  run_cmake_with_options(Debian6)
-
-  run_cmake_with_options(UserFallbackScript)
-
-endif()
+run_cmake(UserFallbackScript)
-- 
cgit v0.12