Add target_compile_features command.

This can be used to set the compiler features required by particular
targets. An error is issued at CMake time if the compiler does not
support the required feature. If a language dialect flag is required
by the features used, that will be added automatically.

Base the target_compile_features command on cmTargetPropCommandBase. This
gives us 'free' handling of IMPORTED, ALIAS, INTERFACE, non-compilable
and missing targets.

Source/CMakeLists.txt

@@ -346,6 +346,7 @@ foreach(command_file
     cmSourceGroupCommand
     cmSubdirDependsCommand
     cmTargetCompileDefinitionsCommand
+    cmTargetCompileFeaturesCommand
     cmTargetCompileOptionsCommand
     cmTargetIncludeDirectoriesCommand
     cmTargetSourcesCommand

Source/cmTargetCompileFeaturesCommand.cxx

@@ -0,0 +1,70 @@
+/*============================================================================
+  CMake - Cross Platform Makefile Generator
+  Copyright 2013 Stephen Kelly <steveire@gmail.com>
+
+  Distributed under the OSI-approved BSD License (the "License");
+  see accompanying file Copyright.txt for details.
+
+  This software is distributed WITHOUT ANY WARRANTY; without even the
+  implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+  See the License for more information.
+============================================================================*/
+#include "cmTargetCompileFeaturesCommand.h"
+
+bool cmTargetCompileFeaturesCommand::InitialPass(
+  std::vector<std::string> const& args,
+  cmExecutionStatus &)
+{
+  return this->HandleArguments(args, "COMPILE_FEATURES", NO_FLAGS);
+}
+
+void cmTargetCompileFeaturesCommand
+::HandleImportedTarget(const std::string &tgt)
+{
+  cmOStringStream e;
+  e << "Cannot specify compile features for imported target \""
+    << tgt << "\".";
+  this->Makefile->IssueMessage(cmake::FATAL_ERROR, e.str());
+}
+
+void cmTargetCompileFeaturesCommand
+::HandleMissingTarget(const std::string &name)
+{
+  cmOStringStream e;
+  e << "Cannot specify compile features for target \"" << name << "\" "
+       "which is not built by this project.";
+  this->Makefile->IssueMessage(cmake::FATAL_ERROR, e.str());
+}
+
+//----------------------------------------------------------------------------
+std::string cmTargetCompileFeaturesCommand
+::Join(const std::vector<std::string> &content)
+{
+  std::string defs;
+  std::string sep;
+  for(std::vector<std::string>::const_iterator it = content.begin();
+    it != content.end(); ++it)
+    {
+    defs += sep + *it;
+    sep = ";";
+    }
+  return defs;
+}
+
+//----------------------------------------------------------------------------
+bool cmTargetCompileFeaturesCommand
+::HandleDirectContent(cmTarget *tgt, const std::vector<std::string> &content,
+                                   bool, bool)
+{
+  for(std::vector<std::string>::const_iterator it = content.begin();
+    it != content.end(); ++it)
+    {
+    std::string error;
+    if(!this->Makefile->AddRequiredTargetFeature(tgt, *it, &error))
+      {
+      this->SetError(error);
+      return false;
+      }
+    }
+  return true;
+}

Source/cmTargetCompileFeaturesCommand.h

@@ -0,0 +1,41 @@
+/*============================================================================
+  CMake - Cross Platform Makefile Generator
+  Copyright 2013 Stephen Kelly <steveire@gmail.com>
+
+  Distributed under the OSI-approved BSD License (the "License");
+  see accompanying file Copyright.txt for details.
+
+  This software is distributed WITHOUT ANY WARRANTY; without even the
+  implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+  See the License for more information.
+============================================================================*/
+#ifndef cmTargetCompileFeaturesCommand_h
+#define cmTargetCompileFeaturesCommand_h
+
+#include "cmTargetPropCommandBase.h"
+
+class cmTargetCompileFeaturesCommand : public cmTargetPropCommandBase
+{
+  virtual cmCommand* Clone()
+    {
+    return new cmTargetCompileFeaturesCommand;
+    }
+
+  virtual bool InitialPass(std::vector<std::string> const& args,
+                           cmExecutionStatus &status);
+
+  virtual std::string GetName() const { return "target_compile_features";}
+
+  cmTypeMacro(cmTargetCompileFeaturesCommand, cmTargetPropCommandBase);
+
+private:
+  virtual void HandleImportedTarget(const std::string &tgt);
+  virtual void HandleMissingTarget(const std::string &name);
+
+  virtual bool HandleDirectContent(cmTarget *tgt,
+                                   const std::vector<std::string> &content,
+                                   bool prepend, bool system);
+  virtual std::string Join(const std::vector<std::string> &content);
+};
+
+#endif