From: Florian Weimer <fweimer@redhat.com>
Date: Mon, 4 Sep 2017 08:52:28 +0000 (+0200)
Subject: math.h: Warn about an already-defined log macro
X-Git-Tag: glibc-2.27~969
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b38042f51430974642616a60afbbf96fd0b98659;p=thirdparty%2Fglibc.git

math.h: Warn about an already-defined log macro

This is a common programming error, and the cause of the problem is not
always obvious.

<tgmath.h> defines a log macro, but it includes <math.h> before that, so
that is compatible with the warning.
---

diff --git a/ChangeLog b/ChangeLog
index ef4a6edc5ea..a9fb242bf26 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2017-09-04  Florian Weimer  <fweimer@redhat.com>
+
+	* math/math.h: Issue warning if log is defined.
+
 2017-09-04  Joseph Myers  <joseph@codesourcery.com>
 
 	* scripts/build-many-glibcs.py (Context.checkout): Default Linux
diff --git a/math/math.h b/math/math.h
index 547b36d10ed..6c2ad97fb8e 100644
--- a/math/math.h
+++ b/math/math.h
@@ -26,6 +26,11 @@
 #define __GLIBC_INTERNAL_STARTING_HEADER_IMPLEMENTATION
 #include <bits/libc-header-start.h>
 
+#if defined log && defined __GNUC__
+# warning A macro called log was already defined when <math.h> was included.
+# warning This will cause compilation problems.
+#endif
+
 __BEGIN_DECLS
 
 /* Get definitions of __intmax_t and __uintmax_t.  */