cmake: make C_STANDARD and C_EXTENSIONS configurable

Users can now set up cmake with -DC_STANDARD=... or -DC_EXTENSIONS=...
We default to C90 with C_EXTENSIONS=OFF, but callers can override if
they desire.

Author: ethomson

CMakeLists.txt

@@ -90,6 +90,8 @@ endif()
 
 # Modules
 
+include(FeatureSummary)
+include(SetCStandard)
 include(CheckLibraryExists)
 include(CheckFunctionExists)
 include(CheckSymbolExists)
@@ -102,7 +104,6 @@ include(FindStatNsec)
 include(Findfutimens)
 include(GNUInstallDirs)
 include(IdeSplitSources)
-include(FeatureSummary)
 include(EnableWarnings)
 include(DefaultCFlags)
 include(ExperimentalFeatures)

cmake/SetCStandard.cmake

@@ -0,0 +1,24 @@
+if("${C_STANDARD}" STREQUAL "")
+	set(C_STANDARD "90")
+endif()
+if("${C_EXTENSIONS}" STREQUAL "")
+	set(C_EXTENSIONS OFF)
+endif()
+
+if(${C_STANDARD} MATCHES "^[Cc].*")
+	string(REGEX REPLACE "^[Cc]" "" C_STANDARD ${C_STANDARD})
+endif()
+
+if(${C_STANDARD} MATCHES ".*-strict$")
+	string(REGEX REPLACE "-strict$" "" C_STANDARD ${C_STANDARD})
+	set(C_EXTENSIONS OFF)
+
+	add_feature_info("C Standard" ON "C${C_STANDARD} (strict)")
+else()
+	add_feature_info("C Standard" ON "C${C_STANDARD}")
+endif()
+
+function(set_c_standard project)
+	set_target_properties(${project} PROPERTIES C_STANDARD ${C_STANDARD})
+	set_target_properties(${project} PROPERTIES C_EXTENSIONS ${C_EXTENSIONS})
+endfunction()

examples/CMakeLists.txt

@@ -3,8 +3,7 @@
 file(GLOB SRC_EXAMPLES *.c *.h)
 
 add_executable(lg2 ${SRC_EXAMPLES})
-set_target_properties(lg2 PROPERTIES C_STANDARD 90)
-set_target_properties(lg2 PROPERTIES C_EXTENSIONS OFF)
+set_c_standard(lg2)
 
 # Ensure that we do not use deprecated functions internally
 add_definitions(-DGIT_DEPRECATE_HARD)

fuzzers/CMakeLists.txt

@@ -20,8 +20,7 @@ foreach(fuzz_target_src ${SRC_FUZZERS})
 	endif()
 
 	add_executable(${fuzz_target_name} ${${fuzz_target_name}_SOURCES})
-	set_target_properties(${fuzz_target_name} PROPERTIES C_STANDARD 90)
-	set_target_properties(${fuzz_target_name} PROPERTIES C_EXTENSIONS OFF)
+	set_c_standard(${fuzz_target_name})
 	target_include_directories(${fuzz_target_name} PRIVATE ${LIBGIT2_INCLUDES} ${LIBGIT2_DEPENDENCY_INCLUDES})
 	target_include_directories(${fuzz_target_name} SYSTEM PRIVATE ${LIBGIT2_SYSTEM_INCLUDES})
 

src/cli/CMakeLists.txt

@@ -40,8 +40,7 @@ add_executable(git2_cli ${CLI_SRC_C} ${CLI_SRC_OS} ${CLI_OBJECTS}
 	${LIBGIT2_DEPENDENCY_OBJECTS})
 target_link_libraries(git2_cli ${CLI_LIBGIT2_LIBRARY} ${LIBGIT2_SYSTEM_LIBS})
 
-set_target_properties(git2_cli PROPERTIES C_STANDARD 90)
-set_target_properties(git2_cli PROPERTIES C_EXTENSIONS OFF)
+set_c_standard(git2_cli)
 set_target_properties(git2_cli PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${libgit2_BINARY_DIR})
 set_target_properties(git2_cli PROPERTIES OUTPUT_NAME ${LIBGIT2_FILENAME})
 

src/libgit2/CMakeLists.txt

@@ -2,8 +2,7 @@
 # git library functionality.
 
 add_library(libgit2 OBJECT)
-set_target_properties(libgit2 PROPERTIES C_STANDARD 90)
-set_target_properties(libgit2 PROPERTIES C_EXTENSIONS OFF)
+set_c_standard(libgit2)
 
 include(PkgBuildConfig)
 

src/util/CMakeLists.txt

@@ -1,8 +1,7 @@
 # util: a shared library for common utility functions for libgit2 projects
 
 add_library(util OBJECT)
-set_target_properties(util PROPERTIES C_STANDARD 90)
-set_target_properties(util PROPERTIES C_EXTENSIONS OFF)
+set_c_standard(util)
 
 configure_file(git2_features.h.in git2_features.h)
 

tests/headertest/CMakeLists.txt

@@ -3,8 +3,8 @@
 # even when they have aggressive C90 warnings enabled.
 
 add_executable(headertest headertest.c)
-set_target_properties(headertest PROPERTIES C_STANDARD 90)
-set_target_properties(headertest PROPERTIES C_EXTENSIONS OFF)
+set_c_standard(headertest)
+
 target_include_directories(headertest PRIVATE ${LIBGIT2_INCLUDES})
 
 if (MSVC)

tests/libgit2/CMakeLists.txt

@@ -39,9 +39,8 @@ set_source_files_properties(
 	PROPERTIES OBJECT_DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/clar.suite)
 
 add_executable(libgit2_tests ${SRC_CLAR} ${SRC_TEST} ${LIBGIT2_OBJECTS})
+set_c_standard(libgit2_tests)
 
-set_target_properties(libgit2_tests PROPERTIES C_STANDARD 90)
-set_target_properties(libgit2_tests PROPERTIES C_EXTENSIONS OFF)
 set_target_properties(libgit2_tests PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR})
 target_include_directories(libgit2_tests PRIVATE ${TEST_INCLUDES} ${LIBGIT2_INCLUDES} ${LIBGIT2_DEPENDENCY_INCLUDES})
 target_include_directories(libgit2_tests SYSTEM PRIVATE ${LIBGIT2_SYSTEM_INCLUDES})

tests/util/CMakeLists.txt

@@ -38,9 +38,8 @@ set_source_files_properties(
 	PROPERTIES OBJECT_DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/clar.suite)
 
 add_executable(util_tests ${SRC_CLAR} ${SRC_TEST} ${LIBGIT2_OBJECTS})
+set_c_standard(util_tests)
 
-set_target_properties(util_tests PROPERTIES C_STANDARD 90)
-set_target_properties(util_tests PROPERTIES C_EXTENSIONS OFF)
 set_target_properties(util_tests PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${libgit2_BINARY_DIR})
 
 target_include_directories(util_tests PRIVATE ${TEST_INCLUDES} ${LIBGIT2_INCLUDES} ${LIBGIT2_DEPENDENCY_INCLUDES})