VS: Add CMAKE_GENERATOR_PLATFORM field to control Windows SDK selection

Add a `version=` field to explicitly control the SDK version selection
without relying on `CMAKE_SYSTEM_VERSION`.

Fixes: #16713

5 files changed, 92 insertions, 3 deletions

diff --git a/Source/cmGlobalVisualStudio10Generator.cxx b/Source/cmGlobalVisualStudio10Generator.cxx
index 41d54e5..321f377 100644
--- a/Source/cmGlobalVisualStudio10Generator.cxx
+++ b/Source/cmGlobalVisualStudio10Generator.cxx
@@ -531,6 +531,9 @@ bool cmGlobalVisualStudio10Generator::InitializePlatform(cmMakefile* mf)
     if (!this->InitializePlatformWindows(mf)) {
       return false;
     }
+  } else if (!this->SystemName.empty() &&
+             !this->VerifyNoGeneratorPlatformVersion(mf)) {
+    return false;
   }
   return this->cmGlobalVisualStudio8Generator::InitializePlatform(mf);
 }
@@ -540,6 +543,12 @@ bool cmGlobalVisualStudio10Generator::InitializePlatformWindows(cmMakefile*)
   return true;
 }
 
+bool cmGlobalVisualStudio10Generator::VerifyNoGeneratorPlatformVersion(
+  cmMakefile*, cm::optional<std::string>) const
+{
+  return true;
+}
+
 bool cmGlobalVisualStudio10Generator::SelectWindowsPhoneToolset(
   std::string& toolset) const
 {
diff --git a/Source/cmGlobalVisualStudio10Generator.h b/Source/cmGlobalVisualStudio10Generator.h
index 63cfe72..6917ffc 100644
--- a/Source/cmGlobalVisualStudio10Generator.h
+++ b/Source/cmGlobalVisualStudio10Generator.h
@@ -185,6 +185,8 @@ protected:
 
   bool InitializePlatform(cmMakefile* mf) override;
   virtual bool InitializePlatformWindows(cmMakefile* mf);
+  virtual bool VerifyNoGeneratorPlatformVersion(
+    cmMakefile* mf, cm::optional<std::string> reason = cm::nullopt) const;
 
   virtual bool ProcessGeneratorToolsetField(std::string const& key,
                                             std::string const& value);
diff --git a/Source/cmGlobalVisualStudio14Generator.cxx b/Source/cmGlobalVisualStudio14Generator.cxx
index 87c8a5e..9ae80bb 100644
--- a/Source/cmGlobalVisualStudio14Generator.cxx
+++ b/Source/cmGlobalVisualStudio14Generator.cxx
@@ -142,7 +142,31 @@ bool cmGlobalVisualStudio14Generator::InitializePlatformWindows(cmMakefile* mf)
   if (cmHasLiteralPrefix(this->SystemVersion, "10.0")) {
     return this->SelectWindows10SDK(mf);
   }
-  return true;
+  return this->VerifyNoGeneratorPlatformVersion(mf);
+}
+
+bool cmGlobalVisualStudio14Generator::VerifyNoGeneratorPlatformVersion(
+  cmMakefile* mf, cm::optional<std::string> reason) const
+{
+  if (!this->GeneratorPlatformVersion) {
+    return true;
+  }
+  std::ostringstream e;
+  /* clang-format off */
+  e <<
+    "Generator\n"
+    "  " << this->GetName() << "\n"
+    "given platform specification containing a\n"
+    "  version=" << *this->GeneratorPlatformVersion << "\n"
+    "field.  The version field is not supported when targeting\n"
+    "  " << this->SystemName << " " << this->SystemVersion << "\n"
+    ;
+  /* clang-format on */
+  if (reason) {
+    e << *reason << ".";
+  }
+  mf->IssueMessage(MessageType::FATAL_ERROR, e.str());
+  return false;
 }
 
 bool cmGlobalVisualStudio14Generator::InitializeWindowsStore(cmMakefile* mf)
@@ -170,12 +194,42 @@ bool cmGlobalVisualStudio14Generator::InitializeAndroid(cmMakefile*)
   return true;
 }
 
+bool cmGlobalVisualStudio14Generator::ProcessGeneratorPlatformField(
+  std::string const& key, std::string const& value)
+{
+  if (key == "version") {
+    this->GeneratorPlatformVersion = value;
+    return true;
+  }
+  return false;
+}
+
 bool cmGlobalVisualStudio14Generator::SelectWindows10SDK(cmMakefile* mf)
 {
+  if (this->GeneratorPlatformVersion &&
+      this->GeneratorPlatformVersion->empty()) {
+    mf->IssueMessage(
+      MessageType::FATAL_ERROR,
+      cmStrCat("Generator\n  ", this->GetName(),
+               "\ngiven platform specification with empty\n  version=\n"
+               "field."));
+    return false;
+  }
+
   // Find the default version of the Windows 10 SDK.
   std::string const version = this->GetWindows10SDKVersion(mf);
 
   if (version.empty()) {
+    if (this->GeneratorPlatformVersion) {
+      mf->IssueMessage(
+        MessageType::FATAL_ERROR,
+        cmStrCat("Generator\n  ", this->GetName(),
+                 "\ngiven platform specification with\n  version=",
+                 *this->GeneratorPlatformVersion,
+                 "\nfield, but no Windows SDK with that version was found."));
+      return false;
+    }
+
     if (this->SystemName == "WindowsStore") {
       mf->IssueMessage(
         MessageType::FATAL_ERROR,
@@ -359,7 +413,20 @@ std::string cmGlobalVisualStudio14Generator::GetWindows10SDKVersion(
   // Sort the results to make sure we select the most recent one.
   std::sort(sdks.begin(), sdks.end(), cmSystemTools::VersionCompareGreater);
 
-  // Look for a SDK exactly matching the requested target version.
+  // Look for a SDK exactly matching the requested version, if any.
+  if (this->GeneratorPlatformVersion) {
+    for (std::string const& i : sdks) {
+      if (cmSystemTools::VersionCompareEqual(
+            i, *this->GeneratorPlatformVersion)) {
+        return i;
+      }
+    }
+    // An exact version was requested but not found.
+    // Our caller will issue the error message.
+    return std::string();
+  }
+
+  // Look for a SDK exactly matching the target Windows version.
   for (std::string const& i : sdks) {
     if (cmSystemTools::VersionCompareEqual(i, this->SystemVersion)) {
       return i;
diff --git a/Source/cmGlobalVisualStudio14Generator.h b/Source/cmGlobalVisualStudio14Generator.h
index 0f016b3..f59a323 100644
--- a/Source/cmGlobalVisualStudio14Generator.h
+++ b/Source/cmGlobalVisualStudio14Generator.h
@@ -7,6 +7,8 @@
 #include <memory>
 #include <string>
 
+#include <cm/optional>
+
 #include "cmGlobalVisualStudio12Generator.h"
 
 class cmGlobalGeneratorFactory;
@@ -39,6 +41,12 @@ protected:
   bool IsWindowsStoreToolsetInstalled() const;
 
   bool InitializePlatformWindows(cmMakefile* mf) override;
+  bool VerifyNoGeneratorPlatformVersion(
+    cmMakefile* mf,
+    cm::optional<std::string> reason = cm::nullopt) const override;
+
+  bool ProcessGeneratorPlatformField(std::string const& key,
+                                     std::string const& value) override;
 
   // Used to adjust the max-SDK-version calculation to accommodate user
   // configuration.
@@ -62,4 +70,6 @@ protected:
 private:
   class Factory;
   friend class Factory;
+
+  cm::optional<std::string> GeneratorPlatformVersion;
 };
diff --git a/Source/cmGlobalVisualStudioVersionedGenerator.cxx b/Source/cmGlobalVisualStudioVersionedGenerator.cxx
index f3936ce..f28419a 100644
--- a/Source/cmGlobalVisualStudioVersionedGenerator.cxx
+++ b/Source/cmGlobalVisualStudioVersionedGenerator.cxx
@@ -895,7 +895,8 @@ bool cmGlobalVisualStudioVersionedGenerator::InitializePlatformWindows(
     if (this->Version >= cmGlobalVisualStudioGenerator::VSVersion::VS16 &&
         !cmSystemTools::VersionCompareGreater(this->SystemVersion, "8.1")) {
       this->SetWindowsTargetPlatformVersion("8.1", mf);
-      return true;
+      return this->VerifyNoGeneratorPlatformVersion(
+        mf, "with the Windows 8.1 SDK installed");
     }
     return cmGlobalVisualStudio14Generator::InitializePlatformWindows(mf);
   }