From 1f8a3f7bccfc84b195218ad0086ebd57049c3490 Mon Sep 17 00:00:00 2001
From: Guillem Jover <guillem@hadrons.org>
Date: Tue, 6 Mar 2018 01:39:45 +0100
Subject: Fix function declaration protection for glibc already providing them
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On non-glibc based systems we cannot unconditionally use the
__GLIBC_PREREQ macro as it gets expanded before evaluation. Instead,
if it is undefined, define it to 0.

We should also always declare these functions on non-glibc based
systems. And on systems with a new enough glibc, which provides these
functions, we should still provide the declarations if _GNU_SOURCE
is *not* defined.

Reported-by: Jörg Krause <joerg.krause@embedded.rocks>
---
 include/bsd/stdlib.h    | 3 ++-
 include/bsd/string.h    | 3 ++-
 include/bsd/sys/cdefs.h | 8 ++++++++
 3 files changed, 12 insertions(+), 2 deletions(-)

--- a/include/bsd/stdlib.h
+++ b/include/bsd/stdlib.h
@@ -71,7 +71,8 @@ int sradixsort(const unsigned char **bas
                const unsigned char *table, unsigned endbyte);
 
 void *reallocf(void *ptr, size_t size);
-#if defined(_GNU_SOURCE) && defined(__GLIBC__) && !__GLIBC_PREREQ(2, 26)
+#if !defined(__GLIBC__) || \
+    (defined(__GLIBC__) && (!__GLIBC_PREREQ(2, 26) || !defined(_GNU_SOURCE)))
 void *reallocarray(void *ptr, size_t nmemb, size_t size);
 #endif
 
--- a/include/bsd/string.h
+++ b/include/bsd/string.h
@@ -46,7 +46,8 @@ size_t strlcat(char *dst, const char *sr
 char *strnstr(const char *str, const char *find, size_t str_len);
 void strmode(mode_t mode, char *str);
 
-#if defined(_GNU_SOURCE) && defined(__GLIBC__) && !__GLIBC_PREREQ(2, 25)
+#if !defined(__GLIBC__) || \
+    (defined(__GLIBC__) && (!__GLIBC_PREREQ(2, 25) || !defined(_GNU_SOURCE)))
 void explicit_bzero(void *buf, size_t len);
 #endif
 __END_DECLS
--- a/include/bsd/sys/cdefs.h
+++ b/include/bsd/sys/cdefs.h
@@ -59,6 +59,14 @@
 #endif
 
 /*
+ * On non-glibc based systems, we cannot unconditionally use the
+ * __GLIBC_PREREQ macro as it gets expanded before evaluation.
+ */
+#ifndef __GLIBC_PREREQ
+#define __GLIBC_PREREQ(maj, min) 0
+#endif
+
+/*
  * Some kFreeBSD headers expect those macros to be set for sanity checks.
  */
 #ifndef _SYS_CDEFS_H_
