cmTarget: Transitively evaluate compiler features.

Extend the interface of the target_compile_features command with
PUBLIC and INTERFACE keywords. Populate the INTERFACE_COMPILER_FEATURES
target property if they are set. Consume the INTERFACE_COMPILER_FEATURES
target property from linked dependent targets to determine the final
required compiler features and the compile flag, if needed.

Use the same pattern of origin-debugging which is used for other
build properties.

21 files changed, 203 insertions, 14 deletions

diff --git a/Help/manual/cmake-properties.7.rst b/Help/manual/cmake-properties.7.rst
index 30413ae..a82522d 100644
--- a/Help/manual/cmake-properties.7.rst
+++ b/Help/manual/cmake-properties.7.rst
@@ -151,6 +151,7 @@ Properties on Targets
    /prop_tgt/INSTALL_RPATH_USE_LINK_PATH
    /prop_tgt/INTERFACE_AUTOUIC_OPTIONS
    /prop_tgt/INTERFACE_COMPILE_DEFINITIONS
+   /prop_tgt/INTERFACE_COMPILE_FEATURES
    /prop_tgt/INTERFACE_COMPILE_OPTIONS
    /prop_tgt/INTERFACE_INCLUDE_DIRECTORIES
    /prop_tgt/INTERFACE_LINK_LIBRARIES
diff --git a/Help/prop_tgt/INTERFACE_COMPILE_FEATURES.rst b/Help/prop_tgt/INTERFACE_COMPILE_FEATURES.rst
new file mode 100644
index 0000000..a98e362
--- /dev/null
+++ b/Help/prop_tgt/INTERFACE_COMPILE_FEATURES.rst
@@ -0,0 +1,14 @@
+INTERFACE_COMPILE_FEATURES
+--------------------------
+
+List of public compile requirements for a library.
+
+Targets may populate this property to publish the compiler features
+required to compile against the headers for the target.  Consuming
+targets can add entries to their own :prop_tgt:`COMPILE_FEATURES`
+property such as ``$<TARGET_PROPERTY:foo,INTERFACE_COMPILE_FEATURES>``
+to require the features specified in the interface of ``foo``.
+
+Contents of ``INTERFACE_COMPILE_FEATURES`` may use "generator expressions"
+with the syntax ``$<...>``.  See the :manual:`cmake-generator-expressions(7)`
+manual for available expressions.
diff --git a/Help/variable/CMAKE_DEBUG_TARGET_PROPERTIES.rst b/Help/variable/CMAKE_DEBUG_TARGET_PROPERTIES.rst
index edd8fa1..e200b86 100644
--- a/Help/variable/CMAKE_DEBUG_TARGET_PROPERTIES.rst
+++ b/Help/variable/CMAKE_DEBUG_TARGET_PROPERTIES.rst
@@ -7,7 +7,7 @@ This variable can be populated with a list of properties to generate
 debug output for when evaluating target properties.  Currently it can
 only be used when evaluating the :prop_tgt:`INCLUDE_DIRECTORIES`,
 :prop_tgt:`COMPILE_DEFINITIONS`, :prop_tgt:`COMPILE_OPTIONS`,
-:prop_tgt:`AUTOUIC_OPTIONS`, :prop_tgt:`SOURCES`,
+:prop_tgt:`AUTOUIC_OPTIONS`, :prop_tgt:`SOURCES`, :prop_tgt:`COMPILE_FEATURES`,
 :prop_tgt:`POSITION_INDEPENDENT_CODE` target properties and any other property
 listed in :prop_tgt:`COMPATIBLE_INTERFACE_STRING` and other ``COMPATIBLE_INTERFACE_``
 properties.  It outputs an origin for each entry in the target property.
diff --git a/Source/cmGeneratorExpressionDAGChecker.h b/Source/cmGeneratorExpressionDAGChecker.h
index b3147f7..7217a56 100644
--- a/Source/cmGeneratorExpressionDAGChecker.h
+++ b/Source/cmGeneratorExpressionDAGChecker.h
@@ -26,7 +26,8 @@
   SELECT(F, EvaluatingCompileDefinitions,       COMPILE_DEFINITIONS) \
   SELECT(F, EvaluatingCompileOptions,           COMPILE_OPTIONS) \
   SELECT(F, EvaluatingAutoUicOptions,           AUTOUIC_OPTIONS) \
-  SELECT(F, EvaluatingSources,                  SOURCES)
+  SELECT(F, EvaluatingSources,                  SOURCES) \
+  SELECT(F, EvaluatingCompileFeatures,          COMPILE_FEATURES)
 
 #define CM_FOR_EACH_TRANSITIVE_PROPERTY(F) \
   CM_FOR_EACH_TRANSITIVE_PROPERTY_IMPL(F, CM_SELECT_BOTH)
diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx
index f581806..528b1dc 100644
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -1460,7 +1460,7 @@ void cmLocalGenerator::AddCompileOptions(
       }
     }
   std::vector<std::string> features;
-  target->GetCompileFeatures(features);
+  target->GetCompileFeatures(features, config);
   for(std::vector<std::string>::const_iterator it = features.begin();
       it != features.end(); ++it)
     {
diff --git a/Source/cmTarget.cxx b/Source/cmTarget.cxx
index 09e3339..1d4d84c 100644
--- a/Source/cmTarget.cxx
+++ b/Source/cmTarget.cxx
@@ -166,11 +166,14 @@ public:
                                 CachedLinkInterfaceCompileDefinitionsEntries;
   mutable std::map<std::string, std::vector<TargetPropertyEntry*> >
                                 CachedLinkInterfaceSourcesEntries;
+  mutable std::map<std::string, std::vector<TargetPropertyEntry*> >
+                                CachedLinkInterfaceCompileFeaturesEntries;
 
   mutable std::map<std::string, bool> CacheLinkInterfaceIncludeDirectoriesDone;
   mutable std::map<std::string, bool> CacheLinkInterfaceCompileDefinitionsDone;
   mutable std::map<std::string, bool> CacheLinkInterfaceCompileOptionsDone;
   mutable std::map<std::string, bool> CacheLinkInterfaceSourcesDone;
+  mutable std::map<std::string, bool> CacheLinkInterfaceCompileFeaturesDone;
 };
 
 //----------------------------------------------------------------------------
@@ -205,6 +208,7 @@ cmTargetInternals::~cmTargetInternals()
 {
   deleteAndClear(this->CachedLinkInterfaceIncludeDirectoriesEntries);
   deleteAndClear(this->CachedLinkInterfaceCompileOptionsEntries);
+  deleteAndClear(this->CachedLinkInterfaceCompileFeaturesEntries);
   deleteAndClear(this->CachedLinkInterfaceCompileDefinitionsEntries);
   deleteAndClear(this->CachedLinkInterfaceSourcesEntries);
 }
@@ -228,6 +232,7 @@ cmTarget::cmTarget()
   this->BuildInterfaceIncludesAppended = false;
   this->DebugIncludesDone = false;
   this->DebugCompileOptionsDone = false;
+  this->DebugCompileFeaturesDone = false;
   this->DebugCompileDefinitionsDone = false;
   this->DebugSourcesDone = false;
 }
@@ -2617,18 +2622,114 @@ void cmTarget::GetCompileDefinitions(std::vector<std::string> &list,
 }
 
 //----------------------------------------------------------------------------
-void cmTarget::GetCompileFeatures(std::vector<std::string> &features) const
+static void processCompileFeatures(cmTarget const* tgt,
+      const std::vector<cmTargetInternals::TargetPropertyEntry*> &entries,
+      std::vector<std::string> &options,
+      std::set<std::string> &uniqueOptions,
+      cmGeneratorExpressionDAGChecker *dagChecker,
+      const std::string& config, bool debugOptions)
 {
-  assert(this->GetType() != INTERFACE_LIBRARY);
-  for(std::vector<cmTargetInternals::TargetPropertyEntry*>::const_iterator
-      si = this->Internal->CompileFeaturesEntries.begin();
-      si != this->Internal->CompileFeaturesEntries.end(); ++si)
+  processCompileOptionsInternal(tgt, entries, options, uniqueOptions,
+                                dagChecker, config, debugOptions, "features");
+}
+
+//----------------------------------------------------------------------------
+void cmTarget::GetCompileFeatures(std::vector<std::string> &result,
+                                  const std::string& config) const
+{
+  std::set<std::string> uniqueFeatures;
+  cmListFileBacktrace lfbt;
+
+  cmGeneratorExpressionDAGChecker dagChecker(lfbt,
+                                             this->GetName(),
+                                             "COMPILE_FEATURES",
+                                             0, 0);
+
+  std::vector<std::string> debugProperties;
+  const char *debugProp =
+              this->Makefile->GetDefinition("CMAKE_DEBUG_TARGET_PROPERTIES");
+  if (debugProp)
     {
-    cmSystemTools::ExpandListArgument((*si)->ge->Evaluate(this->Makefile,
-                                        "",
-                                        false,
-                                        this),
-                                      features);
+    cmSystemTools::ExpandListArgument(debugProp, debugProperties);
+    }
+
+  bool debugFeatures = !this->DebugCompileFeaturesDone
+                    && std::find(debugProperties.begin(),
+                                 debugProperties.end(),
+                                 "COMPILE_FEATURES")
+                        != debugProperties.end();
+
+  if (this->Makefile->IsGeneratingBuildSystem())
+    {
+    this->DebugCompileFeaturesDone = true;
+    }
+
+  processCompileFeatures(this,
+                            this->Internal->CompileFeaturesEntries,
+                            result,
+                            uniqueFeatures,
+                            &dagChecker,
+                            config,
+                            debugFeatures);
+
+  if (!this->Internal->CacheLinkInterfaceCompileFeaturesDone[config])
+    {
+    for (std::vector<cmValueWithOrigin>::const_iterator
+        it = this->Internal->LinkImplementationPropertyEntries.begin(),
+        end = this->Internal->LinkImplementationPropertyEntries.end();
+        it != end; ++it)
+      {
+      if (!cmGeneratorExpression::IsValidTargetName(it->Value)
+          && cmGeneratorExpression::Find(it->Value) == std::string::npos)
+        {
+        continue;
+        }
+      {
+      cmGeneratorExpression ge(lfbt);
+      cmsys::auto_ptr<cmCompiledGeneratorExpression> cge =
+                                                        ge.Parse(it->Value);
+      std::string targetResult = cge->Evaluate(this->Makefile, config,
+                                        false, this, 0, 0);
+      if (!this->Makefile->FindTargetToUse(targetResult))
+        {
+        continue;
+        }
+      }
+      std::string featureGenex = "$<TARGET_PROPERTY:" +
+                              it->Value + ",INTERFACE_COMPILE_FEATURES>";
+      if (cmGeneratorExpression::Find(it->Value) != std::string::npos)
+        {
+        // Because it->Value is a generator expression, ensure that it
+        // evaluates to the non-empty string before being used in the
+        // TARGET_PROPERTY expression.
+        featureGenex = "$<$<BOOL:" + it->Value + ">:" + featureGenex + ">";
+        }
+      cmGeneratorExpression ge(it->Backtrace);
+      cmsys::auto_ptr<cmCompiledGeneratorExpression> cge = ge.Parse(
+                                                                featureGenex);
+
+      this->Internal
+        ->CachedLinkInterfaceCompileFeaturesEntries[config].push_back(
+                        new cmTargetInternals::TargetPropertyEntry(cge,
+                                                              it->Value));
+      }
+    }
+
+  processCompileFeatures(this,
+    this->Internal->CachedLinkInterfaceCompileFeaturesEntries[config],
+                            result,
+                            uniqueFeatures,
+                            &dagChecker,
+                            config,
+                            debugFeatures);
+
+  if (!this->Makefile->IsGeneratingBuildSystem())
+    {
+    deleteAndClear(this->Internal->CachedLinkInterfaceCompileFeaturesEntries);
+    }
+  else
+    {
+    this->Internal->CacheLinkInterfaceCompileFeaturesDone[config] = true;
     }
 }
 
diff --git a/Source/cmTarget.h b/Source/cmTarget.h
index fe3ea2b..8984649 100644
--- a/Source/cmTarget.h
+++ b/Source/cmTarget.h
@@ -545,7 +545,8 @@ public:
                          const std::string& config) const;
   void GetAutoUicOptions(std::vector<std::string> &result,
                          const std::string& config) const;
-  void GetCompileFeatures(std::vector<std::string> &features) const;
+  void GetCompileFeatures(std::vector<std::string> &features,
+                          const std::string& config) const;
 
   bool IsNullImpliedByLinkLibraries(const std::string &p) const;
   bool IsLinkInterfaceDependentBoolProperty(const std::string &p,
@@ -712,6 +713,7 @@ private:
   mutable bool DebugCompileOptionsDone;
   mutable bool DebugCompileDefinitionsDone;
   mutable bool DebugSourcesDone;
+  mutable bool DebugCompileFeaturesDone;
   mutable std::set<std::string> LinkImplicitNullProperties;
   bool BuildInterfaceIncludesAppended;
 
diff --git a/Tests/CompileFeatures/CMakeLists.txt b/Tests/CompileFeatures/CMakeLists.txt
index 2114f94..bceb6bb 100644
--- a/Tests/CompileFeatures/CMakeLists.txt
+++ b/Tests/CompileFeatures/CMakeLists.txt
@@ -27,3 +27,10 @@ add_executable(GenexCompileFeatures main.cpp)
 set_property(TARGET GenexCompileFeatures
   PROPERTY COMPILE_FEATURES "$<1:cxx_auto_type>;$<0:not_a_feature>"
 )
+
+add_library(iface INTERFACE)
+set_property(TARGET iface
+  PROPERTY INTERFACE_COMPILE_FEATURES "cxx_auto_type"
+)
+add_executable(IfaceCompileFeatures main.cpp)
+target_link_libraries(IfaceCompileFeatures iface)
diff --git a/Tests/RunCMake/CompileFeatures/NotAFeatureTransitive-result.txt b/Tests/RunCMake/CompileFeatures/NotAFeatureTransitive-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeatureTransitive-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/CompileFeatures/NotAFeatureTransitive-stderr.txt b/Tests/RunCMake/CompileFeatures/NotAFeatureTransitive-stderr.txt
new file mode 100644
index 0000000..ff60e50
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeatureTransitive-stderr.txt
@@ -0,0 +1,2 @@
+CMake Error in CMakeLists.txt:
+  Specified unknown feature "not_a_feature" for target "somelib".
diff --git a/Tests/RunCMake/CompileFeatures/NotAFeatureTransitive.cmake b/Tests/RunCMake/CompileFeatures/NotAFeatureTransitive.cmake
new file mode 100644
index 0000000..7311aec
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeatureTransitive.cmake
@@ -0,0 +1,6 @@
+
+add_library(iface INTERFACE)
+set_property(TARGET iface PROPERTY INTERFACE_COMPILE_FEATURES "not_a_feature")
+
+add_library(somelib STATIC empty.cpp)
+target_link_libraries(somelib iface)
diff --git a/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebug-result.txt b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebug-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebug-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebug-stderr.txt b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebug-stderr.txt
new file mode 100644
index 0000000..60a8e51
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebug-stderr.txt
@@ -0,0 +1,11 @@
+CMake Debug Log at NotAFeature_OriginDebug.cmake:4 \(set_property\):
+  Used compile features for target somelib:
+
+   \* not_a_feature
+
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
+
+
+CMake Error in CMakeLists.txt:
+  Specified unknown feature "not_a_feature" for target "somelib".
diff --git a/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebug.cmake b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebug.cmake
new file mode 100644
index 0000000..350c2ea
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebug.cmake
@@ -0,0 +1,4 @@
+
+set(CMAKE_DEBUG_TARGET_PROPERTIES COMPILE_FEATURES)
+add_library(somelib STATIC empty.cpp)
+set_property(TARGET somelib PROPERTY COMPILE_FEATURES "not_a_feature")
diff --git a/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugGenex-result.txt b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugGenex-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugGenex-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugGenex-stderr.txt b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugGenex-stderr.txt
new file mode 100644
index 0000000..08e20a8
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugGenex-stderr.txt
@@ -0,0 +1,11 @@
+CMake Debug Log at NotAFeature_OriginDebugGenex.cmake:4 \(set_property\):
+  Used compile features for target somelib:
+
+   \* not_a_feature
+
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
+
+
+CMake Error in CMakeLists.txt:
+  Specified unknown feature "not_a_feature" for target "somelib".
diff --git a/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugGenex.cmake b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugGenex.cmake
new file mode 100644
index 0000000..2122981
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugGenex.cmake
@@ -0,0 +1,4 @@
+
+set(CMAKE_DEBUG_TARGET_PROPERTIES COMPILE_FEATURES)
+add_library(somelib STATIC empty.cpp)
+set_property(TARGET somelib PROPERTY COMPILE_FEATURES "$<1:not_a_feature>")
diff --git a/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugTransitive-result.txt b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugTransitive-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugTransitive-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugTransitive-stderr.txt b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugTransitive-stderr.txt
new file mode 100644
index 0000000..23c3305
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugTransitive-stderr.txt
@@ -0,0 +1,11 @@
+CMake Debug Log at NotAFeature_OriginDebugTransitive.cmake:6 \(target_link_libraries\):
+  Used compile features for target somelib:
+
+   \* not_a_feature
+
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
+
+
+CMake Error in CMakeLists.txt:
+  Specified unknown feature "not_a_feature" for target "somelib".
diff --git a/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugTransitive.cmake b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugTransitive.cmake
new file mode 100644
index 0000000..05d0073
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeature_OriginDebugTransitive.cmake
@@ -0,0 +1,6 @@
+
+set(CMAKE_DEBUG_TARGET_PROPERTIES COMPILE_FEATURES)
+add_library(iface INTERFACE)
+set_property(TARGET iface PROPERTY INTERFACE_COMPILE_FEATURES "not_a_feature")
+add_library(somelib STATIC empty.cpp)
+target_link_libraries(somelib iface)
diff --git a/Tests/RunCMake/CompileFeatures/RunCMakeTest.cmake b/Tests/RunCMake/CompileFeatures/RunCMakeTest.cmake
index da9477d..a059900 100644
--- a/Tests/RunCMake/CompileFeatures/RunCMakeTest.cmake
+++ b/Tests/RunCMake/CompileFeatures/RunCMakeTest.cmake
@@ -2,3 +2,7 @@ include(RunCMake)
 
 run_cmake(NotAFeature)
 run_cmake(NotAFeatureGenex)
+run_cmake(NotAFeatureTransitive)
+run_cmake(NotAFeature_OriginDebug)
+run_cmake(NotAFeature_OriginDebugGenex)
+run_cmake(NotAFeature_OriginDebugTransitive)