From 73b5cc9a2676cc7ed671daef333d433dff055805 Mon Sep 17 00:00:00 2001
From: Wouter Wijngaards <wouter@nlnetlabs.nl>
Date: Thu, 3 Mar 2016 15:59:25 +0000
Subject: [PATCH] - configure tests for the weak attribute support by the
 compiler.

git-svn-id: file:///svn/unbound/trunk@3645 be551aaa-1e26-0410-a405-d3ace91eadb9
---
 compat/explicit_bzero.c |  4 ++++
 config.h.in             |  3 +++
 configure               | 42 +++++++++++++++++++++++++++++++++++++++++
 configure.ac            | 23 ++++++++++++++++++++++
 doc/Changelog           |  3 +++
 5 files changed, 75 insertions(+)

diff --git a/compat/explicit_bzero.c b/compat/explicit_bzero.c
index a3ba2798a..5f1c427c2 100644
--- a/compat/explicit_bzero.c
+++ b/compat/explicit_bzero.c
@@ -6,7 +6,11 @@
 #include "config.h"
 #include <string.h>
 
+#ifdef HAVE_ATTR_WEAK
 __attribute__((weak)) void
+#else
+void
+#endif
 __explicit_bzero_hook(void *ATTR_UNUSED(buf), size_t ATTR_UNUSED(len))
 {
 }
diff --git a/config.h.in b/config.h.in
index 59277ddf0..c29898862 100644
--- a/config.h.in
+++ b/config.h.in
@@ -42,6 +42,9 @@
 /* Whether the C compiler accepts the "unused" attribute */
 #undef HAVE_ATTR_UNUSED
 
+/* Whether the C compiler accepts the "weak" attribute */
+#undef HAVE_ATTR_WEAK
+
 /* Define to 1 if you have the `chown' function. */
 #undef HAVE_CHOWN
 
diff --git a/configure b/configure
index 69ebea331..24f7fd583 100755
--- a/configure
+++ b/configure
@@ -6118,6 +6118,48 @@ $as_echo "#define HAVE_ATTR_UNUSED 1" >>confdefs.h
 fi
 
 
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether the C compiler (${CC-cc}) accepts the \"weak\" attribute" >&5
+$as_echo_n "checking whether the C compiler (${CC-cc}) accepts the \"weak\" attribute... " >&6; }
+if ${ac_cv_c_weak_attribute+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_cv_c_weak_attribute=no
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+ #include <stdio.h>
+__attribute__((weak)) void f(int x) { printf("%d", x); }
+
+int
+main ()
+{
+
+   f(1);
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  ac_cv_c_weak_attribute="yes"
+else
+  ac_cv_c_weak_attribute="no"
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_c_weak_attribute" >&5
+$as_echo "$ac_cv_c_weak_attribute" >&6; }
+if test $ac_cv_c_weak_attribute = yes; then
+
+$as_echo "#define HAVE_ATTR_WEAK 1" >>confdefs.h
+
+fi
+
+
 if test "$srcdir" != "."; then
 	CPPFLAGS="$CPPFLAGS -I$srcdir"
 fi
diff --git a/configure.ac b/configure.ac
index 089ec62a3..4d9d218f3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -258,6 +258,29 @@ AC_C_INLINE
 ACX_CHECK_FORMAT_ATTRIBUTE
 ACX_CHECK_UNUSED_ATTRIBUTE
 
+AC_DEFUN([CHECK_WEAK_ATTRIBUTE],
+[AC_REQUIRE([AC_PROG_CC])
+AC_MSG_CHECKING(whether the C compiler (${CC-cc}) accepts the "weak" attribute)
+AC_CACHE_VAL(ac_cv_c_weak_attribute,
+[ac_cv_c_weak_attribute=no
+AC_TRY_COMPILE(
+[ #include <stdio.h>
+__attribute__((weak)) void f(int x) { printf("%d", x); }
+], [
+   f(1);
+],
+[ac_cv_c_weak_attribute="yes"],
+[ac_cv_c_weak_attribute="no"])
+])
+
+AC_MSG_RESULT($ac_cv_c_weak_attribute)
+if test $ac_cv_c_weak_attribute = yes; then
+  AC_DEFINE(HAVE_ATTR_WEAK, 1, [Whether the C compiler accepts the "weak" attribute])
+fi
+])dnl End of CHECK_WEAK_ATTRIBUTE
+
+CHECK_WEAK_ATTRIBUTE
+
 if test "$srcdir" != "."; then
 	CPPFLAGS="$CPPFLAGS -I$srcdir"
 fi
diff --git a/doc/Changelog b/doc/Changelog
index 9184d1411..24ec0467d 100644
--- a/doc/Changelog
+++ b/doc/Changelog
@@ -1,3 +1,6 @@
+03 March 2016: Wouter
+	- configure tests for the weak attribute support by the compiler.
+
 02 March 2016: Wouter
 	- 1.5.8 release tag
 	- trunk contains 1.5.9 in development.