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

12 files changed, 24 insertions, 3 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 "")