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73627c7456
In order to cover the largest number of glibc and musl libc versions,
withouth warnings, the decision here is to use `_GNU_SOURCE`,
even if it enables a larger than necessary feature set.
A feature macro is needed, because otherwise the `check_c_source_compiles`
for `HAVE_SYSCALL_GETRANDOM` fails in cases when for example
the default compiler flags include `-std=c99`:
````
src.c:6:13: error: implicit declaration of function ‘syscall’ [-Wimplicit-function-declaration]
6 | syscall(SYS_getrandom, NULL, 0, 0);
| ^~~~~~~
````
But this check should pass, as `SYS_getrandom` is available,
only the declaration of `syscall` in `unistd.h` is conditional behind a macro.
The exact minimal public macros, for enabling this are in `features.h`, and
are version dependent.
According to [5.04](
https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/Archive/man-pages-5.04.tar.gz)
and older versions of the `man 2 syscall` page,
the recommended feature test macro is `_GNU_SOURCE`.
Later on in [5.05](
https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/Archive/man-pages-5.05.tar.gz)
this statement has changed, to provide a smaller minimal feature set.
Namely up to `glibc 2.18` is `_BSD_SOURCE || _SVID_SOURCE`,
but after that the `_DEFAULT_SOURCE` is recommended,
and `_BSD_SOURCE || _SVID_SOURCE` is deprecated, and emits warning in later versions.
Regardless of that the `_GNU_SOURCE` is still fully supported
in every version and is suitable for our purposes.
The musl libc doesn't use `_SVID_SOURCE` at all, but `_BSD_SOURCE` always works,
plus in some newer versions `_DEFAULT_SOURCE` also sets `_BSD_SOURCE`,
but `_GNU_SOURCE` covers the largest set of versions and is unlikely
to be deprecated in the future.
Further info about feature test macros:
In glibc:
https://www.gnu.org/software/libc/manual/html_node/Feature-Test-Macros.html
In musl libc under the `Feature Test Macros Supported by musl` section:
https://musl.libc.org/doc/1.1.24/manual.html
Signed-off-by: Ferenc Géczi <ferenc.gm@gmail.com>
76 lines
2.3 KiB
CMake
76 lines
2.3 KiB
CMake
include(CheckCCompilerFlag)
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include(CheckCSourceCompiles)
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include(CheckIncludeFile)
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include(CheckIncludeFiles)
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include(CheckLibraryExists)
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include(CheckSymbolExists)
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include(TestBigEndian)
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check_include_file("dlfcn.h" HAVE_DLFCN_H)
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check_include_file("fcntl.h" HAVE_FCNTL_H)
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check_include_file("inttypes.h" HAVE_INTTYPES_H)
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check_include_file("memory.h" HAVE_MEMORY_H)
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check_include_file("stdint.h" HAVE_STDINT_H)
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check_include_file("stdlib.h" HAVE_STDLIB_H)
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check_include_file("strings.h" HAVE_STRINGS_H)
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check_include_file("string.h" HAVE_STRING_H)
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check_include_file("sys/stat.h" HAVE_SYS_STAT_H)
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check_include_file("sys/types.h" HAVE_SYS_TYPES_H)
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check_include_file("unistd.h" HAVE_UNISTD_H)
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check_symbol_exists("getpagesize" "unistd.h" HAVE_GETPAGESIZE)
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check_symbol_exists("mmap" "sys/mman.h" HAVE_MMAP)
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check_symbol_exists("getrandom" "sys/random.h" HAVE_GETRANDOM)
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if(EXPAT_WITH_LIBBSD)
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set(CMAKE_REQUIRED_LIBRARIES "${LIB_BSD}")
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set(_bsd "bsd/")
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else()
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set(_bsd "")
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endif()
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check_symbol_exists("arc4random_buf" "${_bsd}stdlib.h" HAVE_ARC4RANDOM_BUF)
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if(NOT HAVE_ARC4RANDOM_BUF)
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check_symbol_exists("arc4random" "${_bsd}stdlib.h" HAVE_ARC4RANDOM)
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endif()
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set(CMAKE_REQUIRED_LIBRARIES)
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#/* Define to 1 if you have the ANSI C header files. */
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check_include_files("stdlib.h;stdarg.h;string.h;float.h" STDC_HEADERS)
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test_big_endian(WORDS_BIGENDIAN)
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#/* 1234 = LIL_ENDIAN, 4321 = BIGENDIAN */
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if(WORDS_BIGENDIAN)
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set(BYTEORDER 4321)
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else(WORDS_BIGENDIAN)
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set(BYTEORDER 1234)
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endif(WORDS_BIGENDIAN)
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if(HAVE_SYS_TYPES_H)
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check_c_source_compiles("
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#include <sys/types.h>
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int main(void) {
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const off_t offset = -123;
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return 0;
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}"
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HAVE_OFF_T)
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endif()
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if(NOT HAVE_OFF_T)
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set(off_t "long")
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endif()
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check_c_source_compiles("
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#define _GNU_SOURCE
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#include <stdlib.h> /* for NULL */
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#include <unistd.h> /* for syscall */
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#include <sys/syscall.h> /* for SYS_getrandom */
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int main(void) {
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syscall(SYS_getrandom, NULL, 0, 0);
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return 0;
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}"
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HAVE_SYSCALL_GETRANDOM)
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check_c_compiler_flag("-fno-strict-aliasing" FLAG_NO_STRICT_ALIASING)
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check_c_compiler_flag("-fvisibility=hidden" FLAG_VISIBILITY)
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check_library_exists(m cos "" _EXPAT_LIBM_FOUND)
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