xz/cmake/tuklib_large_file_support.c...

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#
# tuklib_large_file_support.cmake
#
# If off_t is less than 64 bits by default and -D_FILE_OFFSET_BITS=64
# makes off_t become 64-bit, the CMake option LARGE_FILE_SUPPORT is
# provided (ON by default) and -D_FILE_OFFSET_BITS=64 is added to
# the compile definitions if LARGE_FILE_SUPPORT is ON.
#
# Author: Lasse Collin
#
include("${CMAKE_CURRENT_LIST_DIR}/tuklib_common.cmake")
include(CheckCSourceCompiles)
function(tuklib_large_file_support TARGET_OR_ALL)
# MSVC must be handled specially in the C code.
if(MSVC)
return()
endif()
set(TUKLIB_LARGE_FILE_SUPPORT_TEST
"#include <sys/types.h>
int foo[sizeof(off_t) >= 8 ? 1 : -1];
int main(void) { return 0; }")
check_c_source_compiles("${TUKLIB_LARGE_FILE_SUPPORT_TEST}"
TUKLIB_LARGE_FILE_SUPPORT_BY_DEFAULT)
if(NOT TUKLIB_LARGE_FILE_SUPPORT_BY_DEFAULT)
cmake_push_check_state()
# This needs -D.
list(APPEND CMAKE_REQUIRED_DEFINITIONS "-D_FILE_OFFSET_BITS=64")
check_c_source_compiles("${TUKLIB_LARGE_FILE_SUPPORT_TEST}"
TUKLIB_LARGE_FILE_SUPPORT_WITH_FOB64)
cmake_pop_check_state()
endif()
if(TUKLIB_LARGE_FILE_SUPPORT_WITH_FOB64)
# Show the option only when _FILE_OFFSET_BITS=64 affects sizeof(off_t).
option(LARGE_FILE_SUPPORT
"Use -D_FILE_OFFSET_BITS=64 to support files larger than 2 GiB."
ON)
if(LARGE_FILE_SUPPORT)
# This must not use -D.
tuklib_add_definitions("${TARGET_OR_ALL}" "_FILE_OFFSET_BITS=64")
endif()
endif()
endfunction()