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tuklib: Update tuklib_attr_noreturn for C11/C17 and C23.

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This makes no difference for GCC or Clang as they support
GNU C's __attribute__((__noreturn__)) but this helps with MSVC:

  - VS 2019 version 16.7 and later support _Noreturn if the
    options /std:c11 or /std:c17 are used. This gets handled
    with the check for __STDC_VERSION__ >= 201112.

  - When MSVC isn't in C11/C17 mode, __declspec(noreturn) is used.

C23 will deprecate _Noreturn (and <stdnoreturn.h>)
for [[noreturn]]. This commit anticipates that but
the final __STDC_VERSION__ value isn't known yet.
This commit is contained in:
Lasse Collin 2023-09-08 18:19:26 +03:00
parent 189f725813
commit 90c94dddfd
2 changed files with 23 additions and 3 deletions
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22
src/common/tuklib_common.h
View file

@ -57,8 +57,28 @@
# define TUKLIB_GNUC_REQ(major, minor) 0
#endif
#if TUKLIB_GNUC_REQ(2, 5)
// tuklib_attr_noreturn attribute is used to mark functions as non-returning.
// We cannot use "noreturn" as the macro name because then C23 code that
// uses [[noreturn]] would break as it would expand to [[ [[noreturn]] ]].
//
// tuklib_attr_noreturn must be used at the beginning of function declaration
// to work in all cases. The [[noreturn]] syntax is the most limiting, it
// must be even before any GNU C's __attribute__ keywords:
//
// tuklib_attr_noreturn
// __attribute__((nonnull(1)))
// extern void foo(const char *s);
//
// FIXME: Update __STDC_VERSION__ for the final C23 version. 202000 is used
// by GCC 13 and Clang 15 with -std=c2x.
#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202000
# define tuklib_attr_noreturn [[noreturn]]
#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112
# define tuklib_attr_noreturn _Noreturn
#elif TUKLIB_GNUC_REQ(2, 5)
# define tuklib_attr_noreturn __attribute__((__noreturn__))
#elif defined(_MSC_VER)
# define tuklib_attr_noreturn __declspec(noreturn)
#else
# define tuklib_attr_noreturn
#endif

4
src/common/tuklib_exit.h
View file

@ -18,8 +18,8 @@
TUKLIB_DECLS_BEGIN
#define tuklib_exit TUKLIB_SYMBOL(tuklib_exit)
extern void tuklib_exit(int status, int err_status, int show_error)
tuklib_attr_noreturn;
tuklib_attr_noreturn
extern void tuklib_exit(int status, int err_status, int show_error);
TUKLIB_DECLS_END
#endif