From acd26eedac09749f82646ea1ac0a662109cca7a8 Mon Sep 17 00:00:00 2001
From: Petr Spacek <pspacek@redhat.com>
Date: Fri, 19 Feb 2016 13:39:27 +0100
Subject: [PATCH] Fix build with GCC 4.9+.

GCC 4.9+ is too aggressive when optimizing functions with nonnull
attributes. This removes most of asserts() in the plugin.
GCC 6 adds warnings for these cases.

We are disabling the unwanted condition pruning by adding
-fno-delete-null-pointer-checks argument.
BIND 9 did the same in its commit 603a78708343f063b44affb882ef93bb19a5142a.

Additionally we enable nonnull attribute only when the build is running under
Clang static analyzer or Coverity.

https://bugzilla.redhat.com/show_bug.cgi?id=1307346
---
 configure.ac | 14 ++++++++++++++
 src/util.h   |  8 ++++++--
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index a06708b1a5ee64bb64c80272c10ed1a35670c8d0..48f5cb63c3bb5535fe1da56abe7583e15d4b5f92 100644
--- a/configure.ac
+++ b/configure.ac
@@ -39,6 +39,20 @@ AC_TRY_COMPILE([
 [CFLAGS="$SAVED_CFLAGS"
  AC_MSG_RESULT([no])])
 
+# Check if build chain supports -fno-delete-null-pointer-checks
+# this flag avoids too agressive optimizations which would remove some asserts
+# BIND 9 did the same in its commit 603a78708343f063b44affb882ef93bb19a5142a
+AC_MSG_CHECKING([for -fno-delete-null-pointer-checks compiler flag])
+SAVED_CFLAGS="$CFLAGS"
+CFLAGS="-fno-delete-null-pointer-checks -Werror"
+AC_TRY_COMPILE([
+	extern int fdef(void);
+],[],
+[AC_MSG_RESULT([yes])
+ CFLAGS="$SAVED_CFLAGS -fno-delete-null-pointer-checks"],
+[CFLAGS="$SAVED_CFLAGS"
+ AC_MSG_RESULT([no])])
+
 # Get CFLAGS from isc-config.sh
 AC_ARG_VAR([BIND9_CFLAGS],
            [C compiler flags for bind9, overriding isc-config.sh])
diff --git a/src/util.h b/src/util.h
index 9849ff9b6c38ec1c6dd143440d5b5e584b2ecd51..402503c339a5ab6ca5273cae420e743b9fc252ab 100644
--- a/src/util.h
+++ b/src/util.h
@@ -103,11 +103,15 @@ extern isc_boolean_t verbose_checks; /* from settings.c */
 /* If no argument index list is given to the nonnull attribute,
  * all pointer arguments are marked as non-null. */
 #define ATTR_NONNULLS     ATTR_NONNULL()
-#ifdef __GNUC__
+#if defined(__COVERITY__) || defined(__clang_analyzer__)
 #define ATTR_NONNULL(...) __attribute__((nonnull(__VA_ARGS__)))
-#define ATTR_CHECKRESULT __attribute__((warn_unused_result))
 #else
 #define ATTR_NONNULL(...)
+#endif
+
+#if defined(__GNUC__)
+#define ATTR_CHECKRESULT __attribute__((warn_unused_result))
+#else
 #define ATTR_CHECKRESULT
 #endif
 
-- 
2.5.0