From 809f2473c2c3b653ff9b3a3961135a554948d7fb Mon Sep 17 00:00:00 2001
From: Christoph Biedl <cb@gnupg.org>
Date: Fri, 22 Jan 2021 11:50:32 +0100
Subject: [PATCH] Set -fcommon compile option

--
In gcc 10, the default was changed to -fno-common, triggering linker
errors since the code indeed uses extern declarations in such a way.

Turns out fixing these isn't easy, so rather just restore the previous
behaviour.

GnuPG-bug-id: 5215
Signed-off-by: Christoph Biedl <cb@gnupg.org>
---
 configure.ac | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/configure.ac b/configure.ac
index e5bf1bc1a..9a14c4e28 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1439,6 +1439,20 @@ if test "$GCC" = yes; then
     if test x"$_gcc_psign" = xyes ; then
        CFLAGS="$CFLAGS -Wno-pointer-sign"
     fi
+
+    AC_MSG_CHECKING([if gcc supports -fcommon])
+
+    _gcc_cflags_save=$CFLAGS
+    CFLAGS="-fcommon"
+
+    AC_COMPILE_IFELSE([AC_LANG_PROGRAM([])],_gcc_fcommon=yes,_gcc_fcommon=no)
+    AC_MSG_RESULT($_gcc_fcommon)
+
+    CFLAGS=$_gcc_cflags_save;
+
+    if test x"$_gcc_fcommon" = xyes ; then
+       CFLAGS="$CFLAGS -fcommon"
+    fi
 fi
 
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