C2x makes static_assert and thread_local into keywords, removing the
definitions as macros in assert.h and threads.h. Thus, disable those
macros in those glibc headers for C2x.
The disabling is done based on a combination of language version and
__GNUC_PREREQ, *not* based on __GLIBC_USE (ISOC2X), on the principle
that users of the header (when requesting C11 or later APIs - not
assert.h for C99 and older API versions) should always have the names
static_assert or thread_local available after inclusion of the header,
whether as a keyword or as a macro. Thus, when using a compiler
without the keywords (whether an older compiler, possibly in C2x mode,
or _GNU_SOURCE with any compiler but in an older language mode, for
example) the macros should be defined, even when C2x APIs have been
requested. The __GNUC_PREREQ conditionals here may well need updating
with the versions of other compilers that gained support for these
keywords in C2x mode.
Tested for x86_64.
#endif /* NDEBUG. */
-#if defined __USE_ISOC11 && !defined __cplusplus
+#if (defined __USE_ISOC11 \
+ && (!defined __STDC_VERSION__ \
+ || __STDC_VERSION__ <= 201710L \
+ || !__GNUC_PREREQ (13, 0)) \
+ && !defined __cplusplus)
# undef static_assert
# define static_assert _Static_assert
#endif
#include <bits/thread-shared-types.h>
#include <bits/types/struct_timespec.h>
-#ifndef __cplusplus
+#if (!defined __STDC_VERSION__ \
+ || __STDC_VERSION__ <= 201710L \
+ || !__GNUC_PREREQ (13, 0)) && !defined __cplusplus
# define thread_local _Thread_local
#endif