This patch enables the Wzero-as-null-pointer-constant for C.
Bootstrapped and regression tested on x86_64.
c: add Wzero-as-null-pointer-constant [PR117059]
Add warnings for the use of zero as a null pointer constant to the C FE.
PR c/117059
gcc/c-family/ChangeLog:
* c.opt (Wzero-as-null-pointer-constant): Enable for C and ObjC.
gcc/c/ChangeLog:
* c-typeck.cc (parse_build_binary_op): Add warning.
(build_conditional_expr): Add warning.
(convert_for_assignment): Add warning.
gcc/testsuite/ChangeLog:
* gcc.dg/Wzero-as-null-pointer-constant.c: New test.
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 9b9f5e744f6..b4e967ce000 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -1632,7 +1632,7 @@ C ObjC C++ ObjC++ Var(warn_xor_used_as_pow) Warning
Init(1)
Warn about xor operators where it appears the user meant exponentiation.
Wzero-as-null-pointer-constant
-C++ ObjC++ Var(warn_zero_as_null_pointer_constant) Warning
+C ObjC C++ ObjC++ Var(warn_zero_as_null_pointer_constant) Warning
Warn when a literal '0' is used as null pointer.
Wzero-length-bounds
diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index 3fdf3437bf5..0266d685933 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -4600,15 +4600,24 @@ parser_build_binary_op (location_t location, enum
tree_code code,
"comparison with string literal results in unspecified "
"behavior");
- if (true
- && TREE_CODE_CLASS (code) == tcc_comparison
- && ((TREE_CODE (type1) == POINTER_TYPE
- && TREE_CODE (type2) == INTEGER_TYPE
- && null_pointer_constant_p (arg2.value))
- || (TREE_CODE (type2) == POINTER_TYPE
- && TREE_CODE (type1) == INTEGER_TYPE
- && null_pointer_constant_p (arg1.value))))
- warning_at (location, 0, "zero as null pointer constant");
+ if (warn_zero_as_null_pointer_constant
+ && c_inhibit_evaluation_warnings == 0
+ && TREE_CODE_CLASS (code) == tcc_comparison)
+ {
+ if ((TREE_CODE (type1) == POINTER_TYPE
+ || TREE_CODE (type1) == NULLPTR_TYPE)
+ && TREE_CODE (type2) == INTEGER_TYPE
+ && null_pointer_constant_p (arg2.value))
+ warning_at (arg2.get_location(), OPT_Wzero_as_null_pointer_constant,
+ "zero as null pointer constant");
+
+ if ((TREE_CODE (type2) == POINTER_TYPE
+ || TREE_CODE (type2) == NULLPTR_TYPE)
+ && TREE_CODE (type1) == INTEGER_TYPE
+ && null_pointer_constant_p (arg1.value))
+ warning_at (arg1.get_location(), OPT_Wzero_as_null_pointer_constant,
+ "zero as null pointer constant");
+ }
if (warn_array_compare
&& TREE_CODE_CLASS (code) == tcc_comparison
@@ -5975,6 +5984,20 @@ build_conditional_expr (location_t colon_loc, tree
ifexp, bool ifexp_bcp,
t1, t2);
}
+ if (warn_zero_as_null_pointer_constant
+ && c_inhibit_evaluation_warnings == 0)
+ {
+ if ((code1 == POINTER_TYPE || code1 == NULLPTR_TYPE)
+ && code2 == INTEGER_TYPE && null_pointer_constant_p (orig_op2))
+ warning_at (op2_loc, OPT_Wzero_as_null_pointer_constant,
+ "zero as null pointer constant");
+
+ if ((code2 == POINTER_TYPE || code2 == NULLPTR_TYPE)
+ && code1 == INTEGER_TYPE && null_pointer_constant_p (orig_op1))
+ warning_at (op1_loc, OPT_Wzero_as_null_pointer_constant,
+ "zero as null pointer constant");
+ }
+
/* Quickly detect the usual case where op1 and op2 have the same type
after promotion. */
if (TYPE_MAIN_VARIANT (type1) == TYPE_MAIN_VARIANT (type2))
@@ -8406,8 +8429,9 @@ convert_for_assignment (location_t location, location_t
expr_loc, tree type,
|| coder == NULLPTR_TYPE
|| coder == BITINT_TYPE))
{
- if (null_pointer_constant)
- warning_at (location, 0, "zero as null pointer constant");
+ if (null_pointer_constant && c_inhibit_evaluation_warnings == 0)
+ warning_at (location, OPT_Wzero_as_null_pointer_constant,
+ "zero as null pointer constant");
/* An explicit constant 0 or type nullptr_t can convert to a pointer,
or one that results from arithmetic, even including a cast to
diff --git a/gcc/testsuite/gcc.dg/Wzero-as-null-pointer-constant.c
b/gcc/testsuite/gcc.dg/Wzero-as-null-pointer-constant.c
new file mode 100644
index 00000000000..f493b2ea2c7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wzero-as-null-pointer-constant.c
@@ -0,0 +1,31 @@
+/* { dg-do compile } */
+/* { dg-options "-std=c23 -Wzero-as-null-pointer-constant" } */
+
+#define NULL (void*)0
+
+void foo(void*);
+void bar()
+{
+ foo(0); /* { dg-warning "zero as null pointer
constant" } */
+ foo(NULL);
+
+ void *p = 0; /* { dg-warning "zero as null pointer
constant" } */
+ void *r = NULL;
+ void *q = { 0 }; /* { dg-warning "zero as null pointer
constant" } */
+ void *s = { NULL };
+ struct { void *q; } x = { 0 }; /* { dg-warning "zero as null pointer
constant" } */
+ struct { void *q; } y = { NULL };
+
+ 1 ? 0 : p; /* { dg-warning "zero as null pointer
constant" } */
+ 1 ? p : 0; /* { dg-warning "zero as null pointer
constant" } */
+ 1 ? 0 : NULL; /* { dg-warning "zero as null pointer
constant" } */
+ 1 ? NULL : 0; /* { dg-warning "zero as null pointer
constant" } */
+
+ if (p == 0); /* { dg-warning "zero as null pointer
constant" } */
+ if (0 == p); /* { dg-warning "zero as null pointer
constant" } */
+ if (NULL == 0); /* { dg-warning "zero as null pointer
constant" } */
+ if (0 == NULL); /* { dg-warning "zero as null pointer
constant" } */
+ if (0 == nullptr); /* { dg-warning "zero as null pointer
constant" } */
+ if (nullptr == 0); /* { dg-warning "zero as null pointer
constant" } */
+}
+
