Simplify clock_gettime Autoconf check #13537
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The clock_gettime() is found in libc on modern systems, except on Solaris <= 10 and possible similar systems, it is in the rt library. This checks if clock_gettime() exists in the libc, then it checks if rt library has clock_gettime, prepends it to LIBS and defines the HAVE_CLOCK_GETTIME symbol with the template from the AC_CHECK_FUNCS. The ac_cv_func_clock_gettime is a cache variable set by AC_CHECK_FUNCS.
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Do all systems have CLOCK_MONOTONIC? |
Not necessary. Modern systems have it if they have clock_gettime, yes. I think some older glibc versions don't have it (happened on some older macOS versions). The CLOCK_MONOTONIC is checked in the C code together with the HAVE_CLOCK_GETTIME: #if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
Otherwise, it can be considered to be present everywhere today, yes. Theoretically not, but in practice it is. And the ext/opcache/jit/ir uses it unconditionally, for now. I think that's ok until we run into issues. |
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The clock_gettime() is found in libc on modern systems, except on Solaris <= 10 and possible similar systems, it is in the rt library.
This checks if clock_gettime() exists in the libc, then it checks if rt library has clock_gettime, prepends it to LIBS and defines the HAVE_CLOCK_GETTIME symbol with the template from the AC_CHECK_FUNCS.
The ac_cv_func_clock_gettime is a cache variable set by AC_CHECK_FUNCS.