From 480430d3977930b8a1aeeec850f14172db0ae94d Mon Sep 17 00:00:00 2001
From: Natanael Copa <ncopa@alpinelinux.org>
Date: Tue, 25 Dec 2018 12:11:35 +0100
Subject: [PATCH] Fix usage of strerror_r

Only GNU libc has implementation of the GNU variant of strerror_r, so
also for __GLIBC__ to determine which strerror_r implemenation to use.

This fixes build with musl libc, which makes some, but not all, GNU
extensions available with _GNU_SOURCE.
---
 src/futils.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/futils.cpp b/src/futils.cpp
index a30acd98..00e71172 100644
--- a/src/futils.cpp
+++ b/src/futils.cpp
@@ -54,7 +54,7 @@
 #include <stdexcept>
 
 #ifdef EXV_HAVE_STRERROR_R
-#ifdef _GNU_SOURCE
+#if defined(__GLIBC__) && defined(_GNU_SOURCE)
 extern char *strerror_r(int errnum, char *buf, size_t n);
 #else
 extern int strerror_r(int errnum, char *buf, size_t n);
@@ -348,7 +348,7 @@ namespace Exiv2 {
         std::ostringstream os;
 #ifdef EXV_HAVE_STRERROR_R
         const size_t n = 1024;
-#ifdef _GNU_SOURCE
+#if defined(__GLIBC__) && defined(_GNU_SOURCE)
         char *buf = 0;
         char buf2[n];
         std::memset(buf2, 0x0, n);