cmake: use CMAKE_C_STANDARD and CMAKE_C_EXTENSIONS

cmake already provides a standard way for callers to override the
C_STANDARD and C_EXTENSIONS properties. Support and document those.

Author: ethomson

CMakeLists.txt

@@ -53,6 +53,8 @@ option(SONAME                  "Set the (SO)VERSION of the target"
 option(DEPRECATE_HARD          "Do not include deprecated functions in the library"    OFF)
 
 # Compilation options
+   set(CMAKE_C_STANDARD        "90" CACHE STRING "The C standard to compile against")
+option(CMAKE_C_EXTENSIONS      "Whether compiler extensions are supported"             OFF)
 option(ENABLE_WERROR           "Enable compilation with -Werror"                       OFF)
 
 if(UNIX)
@@ -91,7 +93,6 @@ endif()
 # Modules
 
 include(FeatureSummary)
-include(SetCStandard)
 include(CheckLibraryExists)
 include(CheckFunctionExists)
 include(CheckSymbolExists)

README.md

@@ -378,8 +378,8 @@ linker. These flags may be useful for cross-compilation or specialized
 setups.
 
 - `CMAKE_C_FLAGS`: Set your own compiler flags
-- `C_STANDARD`: the C standard to compile against; defaults to `C90`
-- `C_EXTENSIONS`: whether compiler extensions are supported; defaults to `OFF`
+- `CMAKE_C_STANDARD`: the C standard to compile against; defaults to `C90`
+- `CMAKE_C_EXTENSIONS`: whether compiler extensions are supported; defaults to `OFF`
 - `CMAKE_FIND_ROOT_PATH`: Override the search path for libraries
 - `ZLIB_LIBRARY`, `OPENSSL_SSL_LIBRARY` AND `OPENSSL_CRYPTO_LIBRARY`:
 Tell CMake where to find those specific libraries

cmake/SetCStandard.cmake

@@ -37,4 +37,3 @@ else()
 endif()
 
 add_library(ntlmclient OBJECT ${SRC_NTLMCLIENT} ${SRC_NTLMCLIENT_UNICODE} ${SRC_NTLMCLIENT_CRYPTO})
-set_target_properties(ntlmclient PROPERTIES C_STANDARD 90)

deps/ntlmclient/CMakeLists.txt

@@ -3,7 +3,6 @@
 file(GLOB SRC_EXAMPLES *.c *.h)
 
 add_executable(lg2 ${SRC_EXAMPLES})
-set_c_standard(lg2)
 
 # Ensure that we do not use deprecated functions internally
 add_definitions(-DGIT_DEPRECATE_HARD)

examples/CMakeLists.txt

@@ -20,7 +20,6 @@ foreach(fuzz_target_src ${SRC_FUZZERS})
 	endif()
 
 	add_executable(${fuzz_target_name} ${${fuzz_target_name}_SOURCES})
-	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})
 

fuzzers/CMakeLists.txt

@@ -40,7 +40,6 @@ 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_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/cli/CMakeLists.txt

@@ -2,7 +2,6 @@
 # git library functionality.
 
 add_library(libgit2 OBJECT)
-set_c_standard(libgit2)
 
 include(PkgBuildConfig)
 

src/libgit2/CMakeLists.txt

@@ -1,7 +1,6 @@
 # util: a shared library for common utility functions for libgit2 projects
 
 add_library(util OBJECT)
-set_c_standard(util)
 
 configure_file(git2_features.h.in git2_features.h)
 

src/util/CMakeLists.txt

@@ -3,7 +3,6 @@
 # even when they have aggressive C90 warnings enabled.
 
 add_executable(headertest headertest.c)
-set_c_standard(headertest)
 
 target_include_directories(headertest PRIVATE ${LIBGIT2_INCLUDES})