Merge topic 'add_explicit_lang_flag_to_compile_object_rule'

74b1c9fc8e Explicitly specify language flag when source LANGUAGE property is set
457170a476 CXX: Compile when possible with explicit `Cxx` language flag set
644d3b86eb C: Compile when possible with explicit `C` language flag set

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !4780

19 files changed, 83 insertions, 5 deletions

diff --git a/Modules/Compiler/AppleClang-C.cmake b/Modules/Compiler/AppleClang-C.cmake
index 2794f52..26a4bbd 100644
--- a/Modules/Compiler/AppleClang-C.cmake
+++ b/Modules/Compiler/AppleClang-C.cmake
@@ -1,6 +1,8 @@
 include(Compiler/Clang)
 __compiler_clang(C)
 
+set(CMAKE_C_COMPILE_OPTIONS_EXPLICIT_LANGUAGE -x c)
+
 if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.0)
   set(CMAKE_C90_STANDARD_COMPILE_OPTION "-std=c90")
   set(CMAKE_C90_EXTENSION_COMPILE_OPTION "-std=gnu90")
diff --git a/Modules/Compiler/AppleClang-CXX.cmake b/Modules/Compiler/AppleClang-CXX.cmake
index 15edc21..611c674 100644
--- a/Modules/Compiler/AppleClang-CXX.cmake
+++ b/Modules/Compiler/AppleClang-CXX.cmake
@@ -1,6 +1,8 @@
 include(Compiler/Clang)
 __compiler_clang(CXX)
 
+set(CMAKE_CXX_COMPILE_OPTIONS_EXPLICIT_LANGUAGE -x c++)
+
 if(NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
   set(CMAKE_CXX_COMPILE_OPTIONS_VISIBILITY_INLINES_HIDDEN "-fvisibility-inlines-hidden")
 endif()
diff --git a/Modules/Compiler/Clang-C.cmake b/Modules/Compiler/Clang-C.cmake
index 7c4a263..fb6ffa7 100644
--- a/Modules/Compiler/Clang-C.cmake
+++ b/Modules/Compiler/Clang-C.cmake
@@ -8,6 +8,8 @@ endif()
 
 if("x${CMAKE_C_COMPILER_FRONTEND_VARIANT}" STREQUAL "xMSVC")
   set(CMAKE_C_CLANG_TIDY_DRIVER_MODE "cl")
+elseif("x${CMAKE_CXX_COMPILER_FRONTEND_VARIANT}" STREQUAL "xGNU")
+  set(CMAKE_C_COMPILE_OPTIONS_EXPLICIT_LANGUAGE -x c)
 endif()
 
 if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 3.4)
diff --git a/Modules/Compiler/Clang-CXX.cmake b/Modules/Compiler/Clang-CXX.cmake
index 789e991..311d2b0 100644
--- a/Modules/Compiler/Clang-CXX.cmake
+++ b/Modules/Compiler/Clang-CXX.cmake
@@ -2,7 +2,9 @@ include(Compiler/Clang)
 __compiler_clang(CXX)
 __compiler_clang_cxx_standards(CXX)
 
+
 if("x${CMAKE_CXX_COMPILER_FRONTEND_VARIANT}" STREQUAL "xGNU")
+  set(CMAKE_CXX_COMPILE_OPTIONS_EXPLICIT_LANGUAGE -x c++)
   set(CMAKE_CXX_COMPILE_OPTIONS_VISIBILITY_INLINES_HIDDEN "-fvisibility-inlines-hidden")
 endif()
 
diff --git a/Modules/Compiler/GNU-C.cmake b/Modules/Compiler/GNU-C.cmake
index ca286b3..8105a77 100644
--- a/Modules/Compiler/GNU-C.cmake
+++ b/Modules/Compiler/GNU-C.cmake
@@ -1,6 +1,8 @@
 include(Compiler/GNU)
 __compiler_gnu(C)
 
+set(CMAKE_C_COMPILE_OPTIONS_EXPLICIT_LANGUAGE -x c)
+
 if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.5)
   set(CMAKE_C90_STANDARD_COMPILE_OPTION "-std=c90")
   set(CMAKE_C90_EXTENSION_COMPILE_OPTION "-std=gnu90")
diff --git a/Modules/Compiler/GNU-CXX.cmake b/Modules/Compiler/GNU-CXX.cmake
index fcaaeab..59ec056 100644
--- a/Modules/Compiler/GNU-CXX.cmake
+++ b/Modules/Compiler/GNU-CXX.cmake
@@ -1,6 +1,8 @@
 include(Compiler/GNU)
 __compiler_gnu(CXX)
 
+set(CMAKE_CXX_COMPILE_OPTIONS_EXPLICIT_LANGUAGE -x c++)
+
 if (WIN32)
   if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.6)
     set(CMAKE_CXX_COMPILE_OPTIONS_VISIBILITY_INLINES_HIDDEN "-fno-keep-inline-dllexport")
diff --git a/Modules/Compiler/Intel-C.cmake b/Modules/Compiler/Intel-C.cmake
index ec3bfd8..322f63d 100644
--- a/Modules/Compiler/Intel-C.cmake
+++ b/Modules/Compiler/Intel-C.cmake
@@ -28,6 +28,8 @@ if("x${CMAKE_C_SIMULATE_ID}" STREQUAL "xMSVC")
 
 else()
 
+  set(CMAKE_C_COMPILE_OPTIONS_EXPLICIT_LANGUAGE -x c)
+
   if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 15.0.0)
     set(CMAKE_C11_STANDARD_COMPILE_OPTION "-std=c11")
     set(CMAKE_C11_EXTENSION_COMPILE_OPTION "-std=gnu11")
diff --git a/Modules/Compiler/Intel-CXX.cmake b/Modules/Compiler/Intel-CXX.cmake
index 1ed1b08..47d5672 100644
--- a/Modules/Compiler/Intel-CXX.cmake
+++ b/Modules/Compiler/Intel-CXX.cmake
@@ -37,6 +37,8 @@ if("x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
 
 else()
 
+  set(CMAKE_CXX_COMPILE_OPTIONS_EXPLICIT_LANGUAGE -x c++)
+
   if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 18.0.0)
     set(CMAKE_CXX17_STANDARD_COMPILE_OPTION "-std=c++17")
     set(CMAKE_CXX17_EXTENSION_COMPILE_OPTION "-std=gnu++17")
diff --git a/Modules/Compiler/XL-C.cmake b/Modules/Compiler/XL-C.cmake
index 2077bda..78c44d5 100644
--- a/Modules/Compiler/XL-C.cmake
+++ b/Modules/Compiler/XL-C.cmake
@@ -6,6 +6,8 @@ string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
 # -qthreaded = Ensures that all optimizations will be thread-safe
 string(APPEND CMAKE_C_FLAGS_INIT " -qthreaded")
 
+set(CMAKE_C_COMPILE_OPTIONS_EXPLICIT_LANGUAGE -qsourcetype=c)
+
 if (CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 10.1)
   set(CMAKE_C90_STANDARD_COMPILE_OPTION "-qlanglvl=stdc89")
   set(CMAKE_C90_EXTENSION_COMPILE_OPTION "-qlanglvl=extc89")
diff --git a/Modules/Compiler/XL-CXX.cmake b/Modules/Compiler/XL-CXX.cmake
index 41e3e11..3b911f3 100644
--- a/Modules/Compiler/XL-CXX.cmake
+++ b/Modules/Compiler/XL-CXX.cmake
@@ -6,6 +6,8 @@ string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
 # -qthreaded = Ensures that all optimizations will be thread-safe
 string(APPEND CMAKE_CXX_FLAGS_INIT " -qthreaded")
 
+set(CMAKE_CXX_COMPILE_OPTIONS_EXPLICIT_LANGUAGE -+)
+
 if (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 10.1)
   if(CMAKE_SYSTEM MATCHES "Linux")
     set(CMAKE_CXX98_STANDARD_COMPILE_OPTION "")
@@ -32,6 +34,3 @@ if (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 10.1)
 endif ()
 
 __compiler_check_default_language_standard(CXX 10.1 98)
-
-set(CMAKE_CXX_COMPILE_OBJECT
-  "<CMAKE_CXX_COMPILER> -+ <DEFINES> <INCLUDES> <FLAGS> -o <OBJECT> -c <SOURCE>")
diff --git a/Modules/Compiler/XLClang-C.cmake b/Modules/Compiler/XLClang-C.cmake
index 54c18a6..1668a4d 100644
--- a/Modules/Compiler/XLClang-C.cmake
+++ b/Modules/Compiler/XLClang-C.cmake
@@ -1,6 +1,8 @@
 include(Compiler/XLClang)
 __compiler_xlclang(C)
 
+set(CMAKE_C_COMPILE_OPTIONS_EXPLICIT_LANGUAGE -x c)
+
 if (CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 13.1.1)
   set(CMAKE_C90_STANDARD_COMPILE_OPTION  "-std=c89")
   set(CMAKE_C90_EXTENSION_COMPILE_OPTION "-std=gnu89")
diff --git a/Modules/Compiler/XLClang-CXX.cmake b/Modules/Compiler/XLClang-CXX.cmake
index 9ea3d7c..02638c7 100644
--- a/Modules/Compiler/XLClang-CXX.cmake
+++ b/Modules/Compiler/XLClang-CXX.cmake
@@ -1,6 +1,8 @@
 include(Compiler/XLClang)
 __compiler_xlclang(CXX)
 
+set(CMAKE_CXX_COMPILE_OPTIONS_EXPLICIT_LANGUAGE -x c++)
+
 if (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 13.1.1)
   set(CMAKE_CXX98_STANDARD_COMPILE_OPTION  "")
   set(CMAKE_CXX98_EXTENSION_COMPILE_OPTION "")
diff --git a/Source/cmExtraSublimeTextGenerator.cxx b/Source/cmExtraSublimeTextGenerator.cxx
index 613a943..3e265a0 100644
--- a/Source/cmExtraSublimeTextGenerator.cxx
+++ b/Source/cmExtraSublimeTextGenerator.cxx
@@ -349,6 +349,13 @@ std::string cmExtraSublimeTextGenerator::ComputeFlagsForObject(
   if (language.empty()) {
     language = "C";
   }
+
+  // explicitly add the explicit language flag before any other flag
+  // this way backwards compatibility with user flags is maintained
+  if (source->GetProperty("LANGUAGE")) {
+    lg->AppendFeatureOptions(flags, language, "EXPLICIT_LANGUAGE");
+  }
+
   std::string const& config =
     lg->GetMakefile()->GetSafeDefinition("CMAKE_BUILD_TYPE");
 
diff --git a/Source/cmGlobalXCodeGenerator.cxx b/Source/cmGlobalXCodeGenerator.cxx
index a5ce5d1..4d589ed 100644
--- a/Source/cmGlobalXCodeGenerator.cxx
+++ b/Source/cmGlobalXCodeGenerator.cxx
@@ -819,6 +819,14 @@ cmXCodeObject* cmGlobalXCodeGenerator::CreateXCodeSourceFile(
     default:
       break;
   }
+
+  // explicitly add the explicit language flag before any other flag
+  // this way backwards compatibility with user flags is maintained
+  if (sf->GetProperty("LANGUAGE")) {
+    this->CurrentLocalGenerator->AppendFeatureOptions(flags, lang,
+                                                      "EXPLICIT_LANGUAGE");
+  }
+
   const std::string COMPILE_FLAGS("COMPILE_FLAGS");
   if (cmProp cflags = sf->GetProperty(COMPILE_FLAGS)) {
     lg->AppendFlags(flags, genexInterpreter.Evaluate(*cflags, COMPILE_FLAGS));
diff --git a/Source/cmMakefileTargetGenerator.cxx b/Source/cmMakefileTargetGenerator.cxx
index 8396fa3..6887569 100644
--- a/Source/cmMakefileTargetGenerator.cxx
+++ b/Source/cmMakefileTargetGenerator.cxx
@@ -532,6 +532,13 @@ void cmMakefileTargetGenerator::WriteObjectRuleFiles(
   // Build the set of compiler flags.
   std::string flags;
 
+  // explicitly add the explicit language flag before any other flag
+  // this way backwards compatibility with user flags is maintained
+  if (source.GetProperty("LANGUAGE")) {
+    this->LocalGenerator->AppendFeatureOptions(flags, lang,
+                                               "EXPLICIT_LANGUAGE");
+  }
+
   // Add language-specific flags.
   std::string langFlags = cmStrCat("$(", lang, "_FLAGS", filterArch, ")");
   this->LocalGenerator->AppendFlags(flags, langFlags);
diff --git a/Source/cmNinjaTargetGenerator.cxx b/Source/cmNinjaTargetGenerator.cxx
index d406c99..0c7591a 100644
--- a/Source/cmNinjaTargetGenerator.cxx
+++ b/Source/cmNinjaTargetGenerator.cxx
@@ -188,7 +188,16 @@ std::string cmNinjaTargetGenerator::ComputeFlagsForObject(
     }
   }
 
-  std::string flags = this->GetFlags(language, config, filterArch);
+  std::string flags;
+  // explicitly add the explicit language flag before any other flag
+  // this way backwards compatibility with user flags is maintained
+  if (source->GetProperty("LANGUAGE")) {
+    this->LocalGenerator->AppendFeatureOptions(flags, language,
+                                               "EXPLICIT_LANGUAGE");
+    flags += " ";
+  }
+
+  flags += this->GetFlags(language, config, filterArch);
 
   // Add Fortran format flags.
   if (language == "Fortran") {
diff --git a/Tests/SetLang/CMakeLists.txt b/Tests/SetLang/CMakeLists.txt
index f24e5cb..af90f11 100644
--- a/Tests/SetLang/CMakeLists.txt
+++ b/Tests/SetLang/CMakeLists.txt
@@ -8,3 +8,10 @@ add_executable(SetLang bar.c)
 set_source_files_properties(foo.c bar.c PROPERTIES LANGUAGE CXX)
 target_link_libraries(SetLang foo)
 set_target_properties(SetLang PROPERTIES LINKER_LANGUAGE CXX)
+
+if((CMAKE_C_COMPILER_ID MATCHES "(GNU|Clang|MSVC|Borland|Embarcadero|Intel|TI|XL)"))
+  add_library(zoom zoom.zzz)
+  set_source_files_properties(zoom.zzz PROPERTIES LANGUAGE CXX)
+  target_link_libraries(SetLang zoom)
+  target_compile_definitions(SetLang PRIVATE WITH_ZOOM)
+endif()
diff --git a/Tests/SetLang/bar.c b/Tests/SetLang/bar.c
index b934356..515e8c2 100644
--- a/Tests/SetLang/bar.c
+++ b/Tests/SetLang/bar.c
@@ -1,10 +1,22 @@
 #include <stdio.h>
 
 int foo();
+
+#ifdef WITH_ZOOM
+int zoom();
+#endif
+
 class A
 {
 public:
-  A() { this->i = foo(); }
+  A()
+  {
+    this->i = foo();
+#ifdef WITH_ZOOM
+    i += zoom();
+    i -= zoom();
+#endif
+  }
   int i;
 };
 
diff --git a/Tests/SetLang/zoom.zzz b/Tests/SetLang/zoom.zzz
new file mode 100644
index 0000000..a0c8899
--- /dev/null
+++ b/Tests/SetLang/zoom.zzz
@@ -0,0 +1,7 @@
+int zoom()
+{
+  int r = 10;
+  r++;
+  int ret = r + 10;
+  return ret;
+}