color: Introduce CMAKE_COLOR_DIAGNOSTICS variable

Add a variable to control both makefile color messages and compiler
color diagnostics.

Fixes: #15502

Auxiliary/vim/syntax/cmake.vim

@@ -705,6 +705,7 @@ syn keyword cmakeVariable contained
             \ CMAKE_CODEBLOCKS_COMPILER_ID
             \ CMAKE_CODEBLOCKS_EXCLUDE_EXTERNAL_FILES
             \ CMAKE_CODELITE_USE_TARGETS
+            \ CMAKE_COLOR_DIAGNOSTICS
             \ CMAKE_COLOR_MAKEFILE
             \ CMAKE_COMMAND
             \ CMAKE_COMPILER_2005

Help/manual/cmake-variables.7.rst

@@ -172,6 +172,7 @@ Variables that Change Behavior
    /variable/CMAKE_CODEBLOCKS_COMPILER_ID
    /variable/CMAKE_CODEBLOCKS_EXCLUDE_EXTERNAL_FILES
    /variable/CMAKE_CODELITE_USE_TARGETS
+   /variable/CMAKE_COLOR_DIAGNOSTICS
    /variable/CMAKE_COLOR_MAKEFILE
    /variable/CMAKE_CONFIGURATION_TYPES
    /variable/CMAKE_DEPENDS_IN_PROJECT_ONLY

Help/release/dev/color-diagnostics.rst

@@ -0,0 +1,7 @@
+color-diagnostics
+-----------------
+
+* The :variable:`CMAKE_COLOR_DIAGNOSTICS` variable was added to control
+  color diagnostics generated by compilers.  This variable also controls
+  color buildsystem messages with :ref:`Makefile Generators`, replacing
+  :variable:`CMAKE_COLOR_MAKEFILE`.

Help/variable/CMAKE_COLOR_DIAGNOSTICS.rst

@@ -0,0 +1,35 @@
+CMAKE_COLOR_DIAGNOSTICS
+-----------------------
+
+.. versionadded:: 3.24
+
+Enable color diagnostics throughout.
+
+This variable uses three states: ``ON``, ``OFF`` and not defined.
+
+When not defined:
+
+* :ref:`Makefile Generators` initialize the :variable:`CMAKE_COLOR_MAKEFILE`
+  variable to ``ON``.  It controls color buildsystem messages.
+
+* GNU/Clang compilers are not invoked with any color diagnostics flag.
+
+When ``ON``:
+
+* :ref:`Makefile Generators` produce color buildsystem messages by default.
+  :variable:`CMAKE_COLOR_MAKEFILE` is not initialized, but may be
+  explicitly set to ``OFF`` to disable color buildsystem messages.
+
+* GNU/Clang compilers are invoked with a flag enabling color diagnostics
+  (``-fcolor-diagnostics``).
+
+When ``OFF``:
+
+* :ref:`Makefile Generators` do not produce color buildsystem messages by
+  default.  :variable:`CMAKE_COLOR_MAKEFILE` is not initialized, but may be
+  explicitly set to ``ON`` to enable color buildsystem messages.
+
+* GNU/Clang compilers are invoked with a flag disabling color diagnostics
+  (``-fno-color-diagnostics``).
+
+``CMAKE_COLOR_DIAGNOSTICS`` is not defined by default.

Modules/CMakeGenericSystem.cmake

@@ -48,10 +48,11 @@ set (CMAKE_SKIP_INSTALL_RPATH "NO" CACHE BOOL
 set(CMAKE_VERBOSE_MAKEFILE FALSE CACHE BOOL "If this value is on, makefiles will be generated without the .SILENT directive, and all commands will be echoed to the console during the make.  This is useful for debugging only. With Visual Studio IDE projects all commands are done without /nologo.")
 
 if(CMAKE_GENERATOR MATCHES "Make")
-  set(CMAKE_COLOR_MAKEFILE ON CACHE BOOL
-    "Enable/Disable color output during build."
-    )
+  if(NOT DEFINED CMAKE_COLOR_DIAGNOSTICS)
+    set(CMAKE_COLOR_MAKEFILE ON CACHE BOOL "Enable/Disable color output during build.")
+  endif()
   mark_as_advanced(CMAKE_COLOR_MAKEFILE)
+
   if(DEFINED CMAKE_RULE_MESSAGES)
     set_property(GLOBAL PROPERTY RULE_MESSAGES ${CMAKE_RULE_MESSAGES})
   endif()

Modules/Compiler/Clang.cmake

@@ -114,6 +114,12 @@ else()
     endif()
     set(CMAKE_${lang}_COMPILE_OPTIONS_USE_PCH -Xclang -include-pch -Xclang <PCH_FILE> -Xclang -include -Xclang <PCH_HEADER>)
     set(CMAKE_${lang}_COMPILE_OPTIONS_CREATE_PCH -Xclang -emit-pch -Xclang -include -Xclang <PCH_HEADER> -x ${__pch_header_${lang}})
+
+    # '-fcolor-diagnostics' introduced since Clang 2.6
+    if(CMAKE_${lang}_COMPILER_VERSION VERSION_GREATER_EQUAL 2.6)
+      set(CMAKE_${lang}_COMPILE_OPTIONS_COLOR_DIAGNOSTICS "-fcolor-diagnostics")
+      set(CMAKE_${lang}_COMPILE_OPTIONS_COLOR_DIAGNOSTICS_OFF "-fno-color-diagnostics")
+    endif()
   endmacro()
 endif()
 

Modules/Compiler/GNU.cmake

@@ -119,4 +119,11 @@ macro(__compiler_gnu lang)
     set(CMAKE_${lang}_COMPILE_OPTIONS_USE_PCH -include <PCH_HEADER>)
     set(CMAKE_${lang}_COMPILE_OPTIONS_CREATE_PCH -x ${__pch_header_${lang}} -include <PCH_HEADER>)
   endif()
+
+  # '-fdiagnostics-color=always' introduced since GCC 4.9
+  # https://gcc.gnu.org/gcc-4.9/changes.html
+  if(CMAKE_${lang}_COMPILER_VERSION VERSION_GREATER_EQUAL 4.9)
+    set(CMAKE_${lang}_COMPILE_OPTIONS_COLOR_DIAGNOSTICS "-fdiagnostics-color=always")
+    set(CMAKE_${lang}_COMPILE_OPTIONS_COLOR_DIAGNOSTICS_OFF "-fno-diagnostics-color")
+  endif()
 endmacro()

Source/cmGhsMultiTargetGenerator.cxx

@@ -187,6 +187,7 @@ void cmGhsMultiTargetGenerator::SetCompilerFlags(std::string const& config,
                                           language, config);
     this->LocalGenerator->AddVisibilityPresetFlags(
       flags, this->GeneratorTarget, language);
+    this->LocalGenerator->AddColorDiagnosticsFlags(flags, language);
 
     // Append old-style preprocessor definition flags.
     if (this->Makefile->GetDefineFlags() != " ") {

Source/cmLocalGenerator.cxx

@@ -1609,6 +1609,7 @@ std::vector<BT<std::string>> cmLocalGenerator::GetTargetCompileFlags(
 
   this->AddCMP0018Flags(compileFlags, target, lang, config);
   this->AddVisibilityPresetFlags(compileFlags, target, lang);
+  this->AddColorDiagnosticsFlags(compileFlags, lang);
   this->AppendFlags(compileFlags, mf->GetDefineFlags());
   this->AppendFlags(compileFlags,
                     this->GetFrameworkFlags(lang, config, target));
@@ -2354,6 +2355,29 @@ void cmLocalGenerator::AddPositionIndependentFlags(std::string& flags,
   }
 }
 
+void cmLocalGenerator::AddColorDiagnosticsFlags(std::string& flags,
+                                                const std::string& lang)
+{
+  cmValue diag = this->Makefile->GetDefinition("CMAKE_COLOR_DIAGNOSTICS");
+  if (diag.IsSet()) {
+    std::string colorFlagName;
+    if (diag.IsOn()) {
+      colorFlagName =
+        cmStrCat("CMAKE_", lang, "_COMPILE_OPTIONS_COLOR_DIAGNOSTICS");
+    } else {
+      colorFlagName =
+        cmStrCat("CMAKE_", lang, "_COMPILE_OPTIONS_COLOR_DIAGNOSTICS_OFF");
+    }
+
+    std::vector<std::string> options;
+    this->Makefile->GetDefExpandList(colorFlagName, options);
+
+    for (std::string const& option : options) {
+      this->AppendFlagEscape(flags, option);
+    }
+  }
+}
+
 void cmLocalGenerator::AddConfigVariableFlags(std::string& flags,
                                               const std::string& var,
                                               const std::string& config)

Source/cmLocalGenerator.h

@@ -159,6 +159,7 @@ public:
                                   cmGeneratorTarget const* target,
                                   const std::string& lang,
                                   const std::string& config);
+  void AddColorDiagnosticsFlags(std::string& flags, const std::string& lang);
   //! Append flags to a string.
   virtual void AppendFlags(std::string& flags,
                            const std::string& newFlags) const;

Source/cmLocalUnixMakefileGenerator3.cxx

@@ -133,7 +133,11 @@ void cmLocalUnixMakefileGenerator3::Generate()
   // Record whether some options are enabled to avoid checking many
   // times later.
   if (!this->GetGlobalGenerator()->GetCMakeInstance()->GetIsInTryCompile()) {
-    this->ColorMakefile = this->Makefile->IsOn("CMAKE_COLOR_MAKEFILE");
+    if (this->Makefile->IsSet("CMAKE_COLOR_MAKEFILE")) {
+      this->ColorMakefile = this->Makefile->IsOn("CMAKE_COLOR_MAKEFILE");
+    } else {
+      this->ColorMakefile = this->Makefile->IsOn("CMAKE_COLOR_DIAGNOSTICS");
+    }
   }
   this->SkipPreprocessedSourceRules =
     this->Makefile->IsOn("CMAKE_SKIP_PREPROCESSED_SOURCE_RULES");