From d8d71393c2fde83769d00c2da766a2fa7955ecbb Mon Sep 17 00:00:00 2001
From: Mark Wielaard <mjw@redhat.com>
Date: Wed, 9 Sep 2015 23:26:54 +0200
Subject: [PATCH] Warn when comparing nonnull arguments to NULL in a function.
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GCC might optimize such checks away so warn the user when the function
contains such comparisons.
nn.c: In function ‘foo’:
nn.c:6:27: warning: nonnull argument ‘bar’ compared to NULL [-Wnonnull]
void foo(void *bar) { if (!bar) abort(); }
^
gcc/ChangeLog
* doc/invoke.texi (Wnonnull): Also warns when comparing against NULL.
gcc/c/ChangeLog
* c-typeck.c (build_binary_op): Check and warn when nonnull arg
parm against NULL.
gcc/cp/ChangeLog
* typeck.c (cp_build_binary_op): Check and warn when nonnull arg
parm against NULL.
gcc/testsuite/ChangeLog
* c-c++-common/nonnull-1.c: New test.
---
gcc/ChangeLog | 4 ++++
gcc/c/ChangeLog | 5 +++++
gcc/c/c-typeck.c | 10 ++++++++++
gcc/cp/ChangeLog | 5 +++++
gcc/cp/typeck.c | 10 ++++++++++
gcc/doc/invoke.texi | 3 +++
gcc/testsuite/ChangeLog | 4 ++++
gcc/testsuite/c-c++-common/nonnull-1.c | 28 ++++++++++++++++++++++++++++
8 files changed, 69 insertions(+)
create mode 100644 gcc/testsuite/c-c++-common/nonnull-1.c
@@ -1,3 +1,7 @@
+2015-09-09 Mark Wielaard <mjw@redhat.com>
+
+ * doc/invoke.texi (Wnonnull): Also warns when comparing against NULL.
+
2015-09-09 Kyrylo Tkachov <kyrylo.tkachov@arm.com>
* config/arm/arm.md (*subsi3_compare0): Rename to...
@@ -1,3 +1,8 @@
+2015-09-09 Mark Wielaard <mjw@redhat.com>
+
+ * c-typeck.c (build_binary_op): Check and warn when nonnull arg
+ parm against NULL.
+
2015-09-09 Jakub Jelinek <jakub@redhat.com>
PR c/67501
@@ -10803,6 +10803,11 @@ build_binary_op (location_t location, enum tree_code code,
short_compare = 1;
else if (code0 == POINTER_TYPE && null_pointer_constant_p (orig_op1))
{
+ if (warn_nonnull
+ && TREE_CODE (op0) == PARM_DECL && nonnull_arg_p (op0))
+ warning_at (location, OPT_Wnonnull,
+ "nonnull argument %qD compared to NULL", op0);
+
if (TREE_CODE (op0) == ADDR_EXPR
&& decl_with_nonnull_addr_p (TREE_OPERAND (op0, 0)))
{
@@ -10823,6 +10828,11 @@ build_binary_op (location_t location, enum tree_code code,
}
else if (code1 == POINTER_TYPE && null_pointer_constant_p (orig_op0))
{
+ if (warn_nonnull
+ && TREE_CODE (op1) == PARM_DECL && nonnull_arg_p (op1))
+ warning_at (location, OPT_Wnonnull,
+ "nonnull argument %qD compared to NULL", op1);
+
if (TREE_CODE (op1) == ADDR_EXPR
&& decl_with_nonnull_addr_p (TREE_OPERAND (op1, 0)))
{
@@ -1,3 +1,8 @@
+2015-09-09 Mark Wielaard <mjw@redhat.com>
+
+ * typeck.c (cp_build_binary_op): Check and warn when nonnull arg
+ parm against NULL.
+
2015-09-09 Jakub Jelinek <jakub@redhat.com>
PR c++/67504
@@ -4438,6 +4438,11 @@ cp_build_binary_op (location_t location,
|| (code0 == POINTER_TYPE
&& TYPE_PTR_P (type1) && integer_zerop (op1)))
{
+ if (warn_nonnull
+ && TREE_CODE (op0) == PARM_DECL && nonnull_arg_p (op0))
+ warning_at (location, OPT_Wnonnull,
+ "nonnull argument %qD compared to NULL", op0);
+
if (TYPE_PTR_P (type1))
result_type = composite_pointer_type (type0, type1, op0, op1,
CPO_COMPARISON, complain);
@@ -4477,6 +4482,11 @@ cp_build_binary_op (location_t location,
|| (code1 == POINTER_TYPE
&& TYPE_PTR_P (type0) && integer_zerop (op0)))
{
+ if (warn_nonnull
+ && TREE_CODE (op1) == PARM_DECL && nonnull_arg_p (op1))
+ warning_at (location, OPT_Wnonnull,
+ "nonnull argument %qD compared to NULL", op1);
+
if (TYPE_PTR_P (type0))
result_type = composite_pointer_type (type0, type1, op0, op1,
CPO_COMPARISON, complain);
@@ -3720,6 +3720,9 @@ formats that may yield only a two-digit year.
Warn about passing a null pointer for arguments marked as
requiring a non-null value by the @code{nonnull} function attribute.
+Also warns when comparing an argument marked with the @code{nonnull}
+function attribute against null inside the function.
+
@option{-Wnonnull} is included in @option{-Wall} and @option{-Wformat}. It
can be disabled with the @option{-Wno-nonnull} option.
@@ -1,3 +1,7 @@
+2015-09-09 Mark Wielaard <mjw@redhat.com>
+
+ * c-c++-common/nonnull-1.c: New test.
+
2015-09-09 Kyrylo Tkachov <kyrylo.tkachov@arm.com>
* gcc.target/aarch64/mod_2.x: New file.
new file mode 100644
@@ -0,0 +1,28 @@
+/* Test for the bad usage of "nonnull" function attribute parms. */
+/* */
+/* { dg-do compile } */
+/* { dg-options "-Wnonnull" } */
+
+#include <stddef.h>
+#include <stdlib.h>
+
+void foo(void *bar) __attribute__((nonnull(1)));
+
+void foo(void *bar) { if (!bar) abort(); } /* { dg-warning "null" "argument ‘bar’ compared to NULL" } */
+
+extern int func (char *, char *, char *, char *) __attribute__((nonnull));
+
+int
+func (char *cp1, char *cp2, char *cp3, char *cp4)
+{
+ if (cp1) /* { dg-warning "nonnull argument" "cp1 compared to NULL" } */
+ return 1;
+
+ if (cp2 == NULL) /* { dg-warning "nonnull argument" "cp2 compared to NULL" } */
+ return 2;
+
+ if (NULL != cp3) /* { dg-warning "nonnull argument" "cp3 compared to NULL" } */
+ return 3;
+
+ return (cp4 != 0) ? 0 : 1; /* { dg-warning "nonnull argument" "cp4 compared to NULL" } */
+}
--
2.4.3