This patch was taken from https://gcc.gnu.org/ml/gcc-patches/2015-08/msg00375.html.
It is used by propeller-gcc-4.

Since the 3.0.3 release of gperf (made in May 2007), the generated func
has had the gnu_inline attribute applied to it.  The gcc source however
has not been updated to include that which has lead to a mismatch.

In practice, this hasn't been an issue for two reasons:
(1) Before gcc-5, the default standard was (gnu) C89, and gcc does not
warn or throw an error in this mode.
(2) Starting with gcc-4.8, the compiler driver used to build gcc was
changed to C++, and g++ does not warn or throw an error in this mode.

This error does show up though when using gcc-5 to build gcc-4.7 or
older as then the default is (gnu) C11 and the C compiler driver is
used.  That failure looks like:
In file included from .../gcc-4.7.4/gcc/cp/except.c:990:0:
cfns.gperf: At top level:
cfns.gperf:101:1: error: 'gnu_inline' attribute present on 'libc_name_p'
cfns.gperf:26:14: error: but not here

Whether the compiler should always emit this error regardless of the
active standard or compiler driver is debatable (I think it should be
consistent -- either always do it or never do it).

2015-08-06  Mike Frysinger  <vapier@gentoo.org>

	* cfns.gperf [__GNUC__, __GNUC_STDC_INLINE__]: Apply the
	__gnu_inline__ attribute.
	* cfns.h: Regenerated.
---
 gcc/cp/cfns.gperf | 3 +++
 gcc/cp/cfns.h     | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/gcc/cp/cfns.gperf b/gcc/cp/cfns.gperf
index 68acd3d..953262f 100644
--- a/gcc/cp/cfns.gperf
+++ b/gcc/cp/cfns.gperf
@@ -22,6 +22,9 @@ __inline
 static unsigned int hash (const char *, unsigned int);
 #ifdef __GNUC__
 __inline
+#ifdef __GNUC_STDC_INLINE__
+__attribute__ ((__gnu_inline__))
+#endif
 #endif
 const char * libc_name_p (const char *, unsigned int);
 %}
diff --git a/gcc/cp/cfns.h b/gcc/cp/cfns.h
index 1c6665d..6d00c0e 100644
--- a/gcc/cp/cfns.h
+++ b/gcc/cp/cfns.h
@@ -53,6 +53,9 @@ __inline
 static unsigned int hash (const char *, unsigned int);
 #ifdef __GNUC__
 __inline
+#ifdef __GNUC_STDC_INLINE__
+__attribute__ ((__gnu_inline__))
+#endif
 #endif
 const char * libc_name_p (const char *, unsigned int);
 /* maximum key range = 391, duplicates = 0 */
-- 
2.4.4
scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/machine.scm?id=48bcbef07a773ad4f0b8a07caec2ba1eb6b8bab0&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-12-08 00:47:26 +0100'>2019-12-08</span></td><td><a href='/guix/commit/gnu/machine.scm?id=a1d7920861a8d6c6774149eaf939eb2636942090'>machine: Remove unnecessary record self-referencing bindings.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-12-07 00:59:56 +0100'>2019-12-07</span></td><td><a h<tr><td><span title='2024-06-11 11:59:40 +0100'>2024-06-11</span></td><td><a href='/guix/commit/gnu/packages/pantheon.scm?id=382be5720c972aa3b54f4b7c00bc21f249855723'>gnu: pantheon-calculator: Update to 8.0.0.</a><span <tr><td><span title='2019-08-15 07:43:09 -0400'>2019-08-15</span></td><td><a href='/guix/commit/gnu/machine.scm?id=9c70c460a05b2bc60f3f3602f0a2dba0f79ce86c'>machine: Implement 'roll-back-machine'.</a><span class='msg-avail'>...</span></td><td>Jakob L. Kreuze</td></tr>
<tr><td><span title='2019-08-06 15:48:51 -0400'>2019-08-06</span></td><td><a href='/guix/commit/gnu/machine.scm?id=d97ce20400b5d2967bfbc0e9fbfb99bbb2daed4f'>machine: Rename 'system' field.</a><span class='msg-avail'>...</span></td><td>Jakob L. Kreuze</td></tr>
<tr><td><span title='2019-07-06 02:10:04 -0400'>2019-07-06</span></td><td><a href='/guix/commit/gnu/machine.scm?id=fa9edf09e992db7510c7471486dffc93e1e707e5'>gnu: Add machine type for deployment specifications.</a><span class='msg-avail'>...</span></td><td>Jakob L. Kreuze</td></tr>