>From 3dfe86d1522029f12c84bec55c8fb3c6c9c561dc Mon Sep 17 00:00:00 2001
From: Bruno Haible <bruno@clisp.org>
Date: Sun, 31 Jan 2021 12:41:33 +0100
Subject: [PATCH 3/6] Make it possible to compile free.c separately,
 unconditionally.

* m4/free.m4 (gl_FUNC_FREE): Define HAVE_FREE_POSIX.
* lib/free.c: Don't define rpl_free if not needed.
---
 ChangeLog  |  4 ++++
 lib/free.c | 16 +++++++++++-----
 m4/free.m4 |  7 +++++--
 3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index e9e2b36..b8d5cd7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2021-01-31  Bruno Haible  <bruno@clisp.org>
 
+	Make it possible to compile free.c separately, unconditionally.
+	* m4/free.m4 (gl_FUNC_FREE): Define HAVE_FREE_POSIX.
+	* lib/free.c: Don't define rpl_free if not needed.
+
 	Make it possible to compile realloc.c separately, unconditionally.
 	* modules/realloc-posix (configure.ac): Invoke gl_MODULE_INDICATOR.
 	* lib/realloc.c: Don't define rpl_realloc if not needed.
diff --git a/lib/free.c b/lib/free.c
index 5c89787..3f5968c 100644
--- a/lib/free.c
+++ b/lib/free.c
@@ -19,15 +19,19 @@
 
 #include <config.h>
 
+/* Specification.  */
 #include <stdlib.h>
 
-#include <errno.h>
+/* A function definition is only needed if HAVE_FREE_POSIX is not defined.  */
+#if !HAVE_FREE_POSIX
+
+# include <errno.h>
 
 void
 rpl_free (void *p)
-#undef free
+# undef free
 {
-#if defined __GNUC__ && !defined __clang__
+# if defined __GNUC__ && !defined __clang__
   /* An invalid GCC optimization
      <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98396>
      would optimize away the assignments in the code below, when link-time
@@ -39,9 +43,11 @@ rpl_free (void *p)
   errno = 0;
   free (p);
   errno = err[errno == 0];
-#else
+# else
   int err = errno;
   free (p);
   errno = err;
-#endif
+# endif
 }
+
+#endif
diff --git a/m4/free.m4 b/m4/free.m4
index d671376..a7923b9 100644
--- a/m4/free.m4
+++ b/m4/free.m4
@@ -1,4 +1,4 @@
-# free.m4 serial 5
+# free.m4 serial 6
 # Copyright (C) 2003-2005, 2009-2021 Free Software Foundation, Inc.
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
@@ -40,7 +40,10 @@ AC_DEFUN([gl_FUNC_FREE],
     ])
 
   case $gl_cv_func_free_preserves_errno in
-   *yes) ;;
+   *yes)
+    AC_DEFINE([HAVE_FREE_POSIX], [1],
+      [Define if the 'free' function is guaranteed to preserve errno.])
+    ;;
    *) REPLACE_FREE=1 ;;
   esac
 ])
-- 
2.7.4