Features: Record standards and features for Intel C on UNIX

Record features for Intel C 12.1 and above.  Skip this for now on
Windows (where Intel C simulates MSVC).

Modules/Compiler/Intel-C-FeatureTests.cmake

@@ -0,0 +1,23 @@
+# References:
+#   - https://software.intel.com/en-us/articles/iso-iec-standards-language-conformance-for-intel-c-compiler
+#   - https://software.intel.com/en-us/articles/c99-support-in-intel-c-compiler
+#   - https://software.intel.com/en-us/articles/c11-support-in-intel-c-compiler
+
+# FIXME: Intel C feature detection works only when simulating the GNU compiler.
+if("x${CMAKE_C_SIMULATE_ID}" STREQUAL "xMSVC")
+  return()
+endif()
+
+set(DETECT_C99 "defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L")
+
+#static assert is only around in version 1500 update 2 and above
+set(_cmake_feature_test_c_static_assert "(__INTEL_COMPILER > 1500 || (__INTEL_COMPILER == 1500 && __INTEL_COMPILER_UPDATE > 1) ) && ${DETECT_C99}")
+
+set(_cmake_oldestSupported "__INTEL_COMPILER >= 1110")
+set(Intel_C99 "${_cmake_oldestSupported} && ${DETECT_C99}")
+set(_cmake_feature_test_c_restrict "${Intel_C99}")
+set(_cmake_feature_test_c_variadic_macros "${Intel_C99}")
+set(_cmake_feature_test_c_function_prototypes "${_cmake_oldestSupported}")
+unset(Intel_C99)
+
+unset(DETECT_C99)

Modules/Compiler/Intel-C.cmake

@@ -8,5 +8,55 @@ set(CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-O2 -g -DNDEBUG")
 
 set(CMAKE_DEPFILE_FLAGS_C "-MD -MT <OBJECT> -MF <DEPFILE>")
 
+if(NOT "x${CMAKE_C_SIMULATE_ID}" STREQUAL "xMSVC")
+  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=c11")
+  endif()
+
+  if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 12.1)
+    set(CMAKE_C90_STANDARD_COMPILE_OPTION "-std=c89")
+    set(CMAKE_C90_EXTENSION_COMPILE_OPTION "-std=c89")
+    set(CMAKE_C99_STANDARD_COMPILE_OPTION "-std=c99")
+    set(CMAKE_C99_EXTENSION_COMPILE_OPTION "-std=c99")
+  endif()
+endif()
+
+if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 12.1)
+  if (NOT CMAKE_C_COMPILER_FORCED)
+    if (NOT CMAKE_C_STANDARD_COMPUTED_DEFAULT)
+      message(FATAL_ERROR "CMAKE_C_STANDARD_COMPUTED_DEFAULT should be set for ${CMAKE_C_COMPILER_ID} (${CMAKE_C_COMPILER}) version ${CMAKE_C_COMPILER_VERSION}")
+    endif()
+    set(CMAKE_C_STANDARD_DEFAULT ${CMAKE_C_STANDARD_COMPUTED_DEFAULT})
+  elseif(NOT DEFINED CMAKE_C_STANDARD_DEFAULT)
+    # Compiler id was forced so just guess the default standard level.
+    if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 15.0.0)
+      set(CMAKE_C_STANDARD_DEFAULT 11)
+    else()
+      set(CMAKE_C_STANDARD_DEFAULT 90)
+    endif()
+  endif()
+endif()
+
+macro(cmake_record_c_compile_features)
+  macro(_get_intel_c_features std_version list)
+    record_compiler_features(C "${std_version}" ${list})
+  endmacro()
+
+  set(_result 0)
+  if (NOT "x${CMAKE_C_SIMULATE_ID}" STREQUAL "xMSVC" AND
+      NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 12.1)
+    if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 15.0.0)
+      _get_intel_c_features(${CMAKE_C11_STANDARD_COMPILE_OPTION} CMAKE_C11_COMPILE_FEATURES)
+    endif()
+    if (_result EQUAL 0)
+      _get_intel_c_features(${CMAKE_C99_STANDARD_COMPILE_OPTION} CMAKE_C99_COMPILE_FEATURES)
+    endif()
+    if (_result EQUAL 0)
+      _get_intel_c_features(${CMAKE_C90_STANDARD_COMPILE_OPTION} CMAKE_C90_COMPILE_FEATURES)
+    endif()
+  endif()
+endmacro()
+
 set(CMAKE_C_CREATE_PREPROCESSED_SOURCE "<CMAKE_C_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
 set(CMAKE_C_CREATE_ASSEMBLY_SOURCE "<CMAKE_C_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -S <SOURCE> -o <ASSEMBLY_SOURCE>")

Tests/CompileFeatures/CMakeLists.txt

@@ -226,6 +226,16 @@ if (CMAKE_C_COMPILE_FEATURES)
     list(APPEND expected_defs
       EXPECT_C_STATIC_ASSERT=1
     )
+  elseif (CMAKE_C_COMPILER_ID STREQUAL "Intel")
+    if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 15)
+      list(APPEND expected_defs
+        EXPECT_C_STATIC_ASSERT=1
+        )
+    else()
+      list(APPEND expected_defs
+        EXPECT_C_STATIC_ASSERT=0
+        )
+    endif()
   endif()
 
   list(APPEND expected_defs