cmTarget: Allow populating COMPILE_FEATURES using generator expressions.

Delay validation of the content as a feature if it contains a
generator expression. It will be checked again at generate-time
after evaluation.

10 files changed, 44 insertions, 9 deletions

diff --git a/Help/prop_tgt/COMPILE_FEATURES.rst b/Help/prop_tgt/COMPILE_FEATURES.rst
index b2c6145655..dc328259ca 100644
--- a/Help/prop_tgt/COMPILE_FEATURES.rst
+++ b/Help/prop_tgt/COMPILE_FEATURES.rst
@@ -5,3 +5,7 @@ Compiler features enabled for this target.
 
 The list of features in this property are a subset of the features listed
 in the :variable:`CMAKE_CXX_COMPILE_FEATURES` variable.
+
+Contents of ``COMPILE_FEATURES`` may use "generator expressions" with the
+syntax ``$<...>``.  See the :manual:`cmake-generator-expressions(7)` manual for
+available expressions.
diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx
index 0f8e7dcb4d..f58180698a 100644
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -1459,17 +1459,14 @@ void cmLocalGenerator::AddCompileOptions(
       this->AppendFlagEscape(flags, *i);
       }
     }
-  if (const char* featureProp = target->GetProperty("COMPILE_FEATURES"))
+  std::vector<std::string> features;
+  target->GetCompileFeatures(features);
+  for(std::vector<std::string>::const_iterator it = features.begin();
+      it != features.end(); ++it)
     {
-    std::vector<std::string> features;
-    cmSystemTools::ExpandListArgument(featureProp, features);
-    for(std::vector<std::string>::const_iterator it = features.begin();
-        it != features.end(); ++it)
+     if (!this->Makefile->AddRequiredTargetFeature(target, *it))
       {
-      if (!this->Makefile->AddRequiredTargetFeature(target, *it))
-        {
-        return;
-        }
+      return;
       }
     }
   this->AddCompilerRequirementFlag(flags, target, lang);
diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index 0b3c43e22f..5004a0893f 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -4521,6 +4521,11 @@ bool cmMakefile::
 AddRequiredTargetFeature(cmTarget *target, const std::string& feature,
                          std::string *error) const
 {
+  if (cmGeneratorExpression::Find(feature) != std::string::npos)
+    {
+    target->AppendProperty("COMPILE_FEATURES", feature.c_str());
+    return true;
+    }
   bool isCxxFeature = std::find_if(cmArrayBegin(CXX_FEATURES) + 1,
               cmArrayEnd(CXX_FEATURES), cmStrCmp(feature))
               != cmArrayEnd(CXX_FEATURES);
diff --git a/Source/cmTarget.cxx b/Source/cmTarget.cxx
index 6f53009bb5..09e3339b8a 100644
--- a/Source/cmTarget.cxx
+++ b/Source/cmTarget.cxx
@@ -2617,6 +2617,22 @@ void cmTarget::GetCompileDefinitions(std::vector<std::string> &list,
 }
 
 //----------------------------------------------------------------------------
+void cmTarget::GetCompileFeatures(std::vector<std::string> &features) const
+{
+  assert(this->GetType() != INTERFACE_LIBRARY);
+  for(std::vector<cmTargetInternals::TargetPropertyEntry*>::const_iterator
+      si = this->Internal->CompileFeaturesEntries.begin();
+      si != this->Internal->CompileFeaturesEntries.end(); ++si)
+    {
+    cmSystemTools::ExpandListArgument((*si)->ge->Evaluate(this->Makefile,
+                                        "",
+                                        false,
+                                        this),
+                                      features);
+    }
+}
+
+//----------------------------------------------------------------------------
 void cmTarget::MaybeInvalidatePropertyCache(const std::string& prop)
 {
   // Wipe out maps caching information affected by this property.
diff --git a/Source/cmTarget.h b/Source/cmTarget.h
index da9d0a1b56..fe3ea2b6ec 100644
--- a/Source/cmTarget.h
+++ b/Source/cmTarget.h
@@ -545,6 +545,7 @@ 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;
 
   bool IsNullImpliedByLinkLibraries(const std::string &p) const;
   bool IsLinkInterfaceDependentBoolProperty(const std::string &p,
diff --git a/Tests/CompileFeatures/CMakeLists.txt b/Tests/CompileFeatures/CMakeLists.txt
index 471b560c25..2114f94bb3 100644
--- a/Tests/CompileFeatures/CMakeLists.txt
+++ b/Tests/CompileFeatures/CMakeLists.txt
@@ -22,3 +22,8 @@ add_executable(CompileFeatures main.cpp)
 set_property(TARGET CompileFeatures
   PROPERTY COMPILE_FEATURES "cxx_auto_type"
 )
+
+add_executable(GenexCompileFeatures main.cpp)
+set_property(TARGET GenexCompileFeatures
+  PROPERTY COMPILE_FEATURES "$<1:cxx_auto_type>;$<0:not_a_feature>"
+)
diff --git a/Tests/RunCMake/CompileFeatures/NotAFeatureGenex-result.txt b/Tests/RunCMake/CompileFeatures/NotAFeatureGenex-result.txt
new file mode 100644
index 0000000000..d00491fd7e
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeatureGenex-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/CompileFeatures/NotAFeatureGenex-stderr.txt b/Tests/RunCMake/CompileFeatures/NotAFeatureGenex-stderr.txt
new file mode 100644
index 0000000000..ff60e50a59
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeatureGenex-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/NotAFeatureGenex.cmake b/Tests/RunCMake/CompileFeatures/NotAFeatureGenex.cmake
new file mode 100644
index 0000000000..ad2bd371d1
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NotAFeatureGenex.cmake
@@ -0,0 +1,3 @@
+
+add_library(somelib STATIC empty.cpp)
+set_property(TARGET somelib PROPERTY COMPILE_FEATURES "$<1:not_a_feature>")
diff --git a/Tests/RunCMake/CompileFeatures/RunCMakeTest.cmake b/Tests/RunCMake/CompileFeatures/RunCMakeTest.cmake
index 3c999e67d8..da9477d6a9 100644
--- a/Tests/RunCMake/CompileFeatures/RunCMakeTest.cmake
+++ b/Tests/RunCMake/CompileFeatures/RunCMakeTest.cmake
@@ -1,3 +1,4 @@
 include(RunCMake)
 
 run_cmake(NotAFeature)
+run_cmake(NotAFeatureGenex)