bug#28571: 25.3; Compile error on macOS Sierra

[Alan Third <alan@idiocy.org>]

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On Sun, Sep 24, 2017 at 07:49:55AM +0000, Philipp Stephani wrote:
> Alan Third <alan@idiocy.org> schrieb am Sa., 23. Sep. 2017 um 21:31 Uhr:
> >
> > Is there maybe a test in configure that’s incorrectly identifying this
> > utimens.c stuff as OK?
> >
> >
> I do have configure output like this:
> 
> checking for futimens... yes
> checking for utimensat... yes
> 
> So I think the functions are there, but the compilation shouldn't use them
> since they would make the binary incompatible with old versions of macOS.

I agree. I’ve attached a patch that should sort it.

I’m not 100% sure that DARWIN_OS is the right define to check for, but
it seems more appropriate than any others I can think of.
-- 
Alan Third

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From d77a2e45004f5d6d8496e5fed260774205efe42a Mon Sep 17 00:00:00 2001
From: Alan Third <alan@idiocy.org>
Date: Sun, 24 Sep 2017 12:01:03 +0100
Subject: [PATCH] Fix build on macOS (bug#28571)

* src/conf_post.h (HAVE_FUTIMENS, HAVE_FUTIMESAT) [DARWIN_OS]:
Undefine.
---
 src/conf_post.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/conf_post.h b/src/conf_post.h
index febdb8b8bf..dfdb0aa3eb 100644
--- a/src/conf_post.h
+++ b/src/conf_post.h
@@ -397,3 +397,11 @@ extern int emacs_setenv_TZ (char const *);
 #else
 # define UNINIT /* empty */
 #endif
+
+/* macOS 10.13 supports futimens and futimesat, older versions don't
+   but can appear as though they do.  Disable them entirely to avoid
+   breaking cross-version builds on macOS.  */
+#ifdef DARWIN_OS
+# undef HAVE_FUTIMENS
+# undef HAVE_FUTIMESAT
+#endif
-- 
2.14.1