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glibc/sysdeps/unix/sysv/linux/time64-support.c

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linux: Add helper function to optimize 64-bit time_t fallback support These helper functions are used to optimize the 64-bit time_t support on configurations that requires support for 32-bit time_t fallback (!__ASSUME_TIME64_SYSCALLS). The idea is once the kernel advertises that it does not have 64-bit time_t support, glibc will stop to try issue the 64-bit time_t syscall altogether. For instance: #ifndef __NR_symbol_time64 # define __NR_symbol_time64 __NR_symbol #endif int r; if (supports_time64 ()) { r = INLINE_SYSCALL_CALL (symbol, ...); if (r == 0 || errno != ENOSYS) return r; mark_time64_unsupported (); } #ifndef __ASSUME_TIME64_SYSCALLS <32-bit fallback syscall> #endif return r; On configuration with default 64-bit time_t this optimization should be optimized away by the compiler resulting in no overhead.
2020-08-20 12:18:15 +00:00
/* Auxiliary definitions for 64-bit time_t support.
Update copyright dates with scripts/update-copyrights I used these shell commands: ../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright (cd ../glibc && git commit -am"[this commit message]") and then ignored the output, which consisted lines saying "FOO: warning: copyright statement not found" for each of 6694 files FOO. I then removed trailing white space from benchtests/bench-pthread-locks.c and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this diagnostic from Savannah: remote: *** pre-commit check failed ... remote: *** error: lines with trailing whitespace found remote: error: hook declined to update refs/heads/master
2021-01-02 19:32:25 +00:00
Copyright (C) 2020-2021 Free Software Foundation, Inc.
linux: Add helper function to optimize 64-bit time_t fallback support These helper functions are used to optimize the 64-bit time_t support on configurations that requires support for 32-bit time_t fallback (!__ASSUME_TIME64_SYSCALLS). The idea is once the kernel advertises that it does not have 64-bit time_t support, glibc will stop to try issue the 64-bit time_t syscall altogether. For instance: #ifndef __NR_symbol_time64 # define __NR_symbol_time64 __NR_symbol #endif int r; if (supports_time64 ()) { r = INLINE_SYSCALL_CALL (symbol, ...); if (r == 0 || errno != ENOSYS) return r; mark_time64_unsupported (); } #ifndef __ASSUME_TIME64_SYSCALLS <32-bit fallback syscall> #endif return r; On configuration with default 64-bit time_t this optimization should be optimized away by the compiler resulting in no overhead.
2020-08-20 12:18:15 +00:00
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <time64-support.h>
#ifndef __ASSUME_TIME64_SYSCALLS
int __time64_support = 1;
#endif
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