On 31/01/2018 15:21, Emil Velikov wrote:
On 30 January 2018 at 20:27, Dylan Baker <dy...@pnwbakers.com> wrote:
Quoting Emil Velikov (2018-01-30 10:56:42)
Hi Jon,

On 28 January 2018 at 14:24, Jon Turney <jon.tur...@dronecode.org.uk> wrote:
---
  meson.build | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/meson.build b/meson.build
index 7e194a9f10d..8fdbaa8b8d8 100644
--- a/meson.build
+++ b/meson.build
@@ -935,7 +935,7 @@ elif with_dri_i965 and get_option('shader-cache')
  endif

  # Determine whether or not the rt library is needed for time functions
-if cc.has_function('clock_gettime')
+if cc.has_function('clock_gettime') or (host_machine.system() == 'darwin')

Absolutely no objections against the patch - just a small question.
If the meson/autotools check fails, does this mean that the resulting
binaries are having unresolved reference wrt said symbol?

Thanks
Emil

Not for meson, it builds -Wl,--no-undefined (or it's MSVC equivalent) by
default, so it shouldn't be possible to get unresolved symbols in a binary or
shared library.

Right, the question is why does the test (has_function) fails?

Some misunderstanding going on here, I think. It fails if the function isn't present.

(We then go on to report the failure as being librt not found, not that we couldn't work out how to find clock_gettime, but perhaps that's a separate issue)

A few possible solutions come to mind, but only one with toolchain
handy can confirm.
  - the test is broken (regardless meson/autotools/foo implementation)
  - the symbol is indirectly resolved
The est does not pull libfoo, while the final binary does. Libfoo
pulls libbar with the latter providing the symbol.
  - the final binary is having unresolved reference
  - all the clock_gettime references get 'magically' removed due to the
linker garbage collector

 From a quick search OSX 10.12 (or so) has clock_gettime. But details
are extremely sparse :-(

This change (and the check that autoconf is currently doing) is not needed.

If we're targeting OSX 10.12 or later, clock_gettime() exists.

Commit 990bd49f might have made sense once, but I think now that clock_gettime is used in include/c11/threads_posix.h, we're going to fail to build for OSX prior to 10.12, even when not trying to link with librt.

(I also had a patch to provide an implementation of clock_gettime if the target is an earlier OSX version, but I dropped it as probably not very useful)
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