Fix C99 compatibility issue in the configure script

Related to:

  <https://fedoraproject.org/wiki/Changes/PortingToModernC>
  <https://fedoraproject.org/wiki/Toolchain/PortingToModernC>

grep-configure-c99.patch

@@ -0,0 +1,46 @@
+Work around a recent regression in C99 compatibility in autoconf.
+The configure script was generated with an autoconf prerelease,
+and the issue has been fixed upstream with this commit:
+
+commit bf5a75953b6d504f0405b1ca33b039b8dd39eef4
+Author: Zack Weinberg <zackw@panix.com>
+Date:   Thu Nov 10 12:05:30 2022 -0500
+
+    More fixes for compilers that reject K&R function definitions.
+
+    This fixes all of the remaining failures exposed by running the
+    testsuite with GCC 12 and
+    CC='cc -Wimplicit-function-declaration -Wold-style-definition
+           -Wimplicit-int -Werror'
+    .
+
+    * lib/autoconf/c.m4 (_AC_C_C89_TEST_GLOBALS): Don’t use K&R function
+      definitions.
+    * lib/autoconf/specific.m4 (AC_SYS_RESTARTABLE_SYSCALLS): Likewise.
+      (AC_FUNC_MKTIME): Declare functions taking no arguments as ‘fn (void)’
+      not ‘fn ()’.
+    * lib/autoconf/c.m4 (_AC_C_C99_TEST_GLOBALS): Declare free().
+
+diff --git a/configure b/configure
+index 51bd10995a6f57e8..4bdd3ecca7d2c793 100755
+--- a/configure
++++ b/configure
+@@ -3954,9 +3954,7 @@ struct stat;
+ /* Most of the following tests are stolen from RCS 5.7 src/conf.sh.  */
+ struct buf { int x; };
+ struct buf * (*rcsopen) (struct buf *, struct stat *, int);
+-static char *e (p, i)
+-     char **p;
+-     int i;
++static char *e (char **p, int i)
+ {
+   return p[i];
+ }
+@@ -4007,6 +4005,7 @@ extern int puts (const char *);
+ extern int printf (const char *, ...);
+ extern int dprintf (int, const char *, ...);
+ extern void *malloc (size_t);
++extern void free (void *);
+ 
+ // Check varargs macros.  These examples are taken from C99 6.10.3.5.
+ // dprintf is used instead of fprintf to avoid needing to declare

grep.spec

@@ -1,7 +1,7 @@
 Summary: Pattern matching utilities
 Name: grep
 Version: 3.8
-Release: 1%{?dist}
+Release: 2%{?dist}
 License: GPLv3+
 URL: https://www.gnu.org/software/grep/
 
@@ -12,6 +12,7 @@ Source3: GREP_COLORS
 Source4: grepconf.sh
 # upstream ticket 39445
 Patch0: grep-3.5-help-align.patch
+Patch1: grep-configure-c99.patch
 
 BuildRequires: gcc
 BuildRequires: pcre2-devel
@@ -83,6 +84,9 @@ make check
 %{_libexecdir}/grepconf.sh
 
 %changelog
+* Tue Jan  3 2023 Florian Weimer <fweimer@redhat.com> - 3.8-2
+- Fix C99 compatibility issue in the configure script
+
 * Mon Sep  5 2022 Jaroslav Škarvada <jskarvad@redhat.com> - 3.8-1
 - New version
   Resolves: rhbz#2123935