Description:
------------
Hi, php 8.1.0alpha1 does not build on OS X 10.11 ("El Capitan") and earlier because of:


/path/to/php-8.1.0alpha1/ext/standard/hrtime.c:111:9: warning: implicit declaration of function 'clock_gettime_nsec_np' is invalid in C99 [-Wimplicit-function-declaration]
        return clock_gettime_nsec_np(CLOCK_MONOTONIC_RAW);
               ^
/path/to/php-8.1.0alpha1/ext/standard/hrtime.c:111:31: error: use of undeclared identifier 'CLOCK_MONOTONIC_RAW'
        return clock_gettime_nsec_np(CLOCK_MONOTONIC_RAW);
                                     ^
1 warning and 1 error generated.
make: *** [ext/standard/hrtime.lo] Error 1


Here's a full build log if you would like it:

https://build.macports.org/builders/ports-10.11_x86_64-builder/builds/144512/steps/install-port/logs/stdio

php 8.0.x and earlier were able to build on these older OS X versions.

clock_gettime and related functions were not in the operating system prior to macOS 10.12 ("Sierra").

In php 8.0.x, I already noticed a similar problem with just the opcache extension and I applied a workaround in MacPorts that adds a compatibility implementation of these functions via the MacPorts "legacy support" library. Here's our implementation:

https://github.com/macports/macports-legacy-support/blob/master/include/time.h
https://github.com/macports/macports-legacy-support/blob/master/src/time.c

But now in php 8.1.x the build failure affects php as a whole.

We don't have a compatibility implementation of clock_gettime_nsec_np in MacPorts legacy support yet (https://trac.macports.org/ticket/61691) so we are not able to work around it by adding our library here.

Looks like this problem was caused in php commit a3e55286a676fdf4f5919d219e2a0df93f817211 ("Using a more modern and simpler api available since Sierra (2016).")

Since you had an apparently working implementation before, perhaps you can have a configure test that checks for clock_gettime, uses it if available, and otherwise uses the older implementation.