As reported in bug 112556, GCC wrongly rejects conversion of null
pointer constants with bool or enum type to pointers in
convert_for_assignment (assignment, initialization, argument passing,
return). Fix the code there to allow BOOLEAN_TYPE and ENUMERAL_TYPE;
it already allowed INTEGER_TYPE and BITINT_TYPE.
This bug (together with -std=gnu23 meaning false has type bool rather
than int) has in turn resulted in people thinking they need to fix
code using false as a null pointer constant for C23 compatibility.
While such a usage is certainly questionable, it has nothing to do
with C23 compatibility and the right place for warnings about such
usage is -Wzero-as-null-pointer-constant. I think it would be
appropriate to extend -Wzero-as-null-pointer-constant to cover
BOOLEAN_TYPE, ENUMERAL_TYPE and BITINT_TYPE (in all the various
contexts in which that option generates warnings), though this patch
doesn't do anything about that option.
Bootstrapped with no regressions for x86-64-pc-linux-gnu.
PR c/112556
gcc/c/
* c-typeck.cc (convert_for_assignment): Allow conversion of
ENUMERAL_TYPE and BOOLEAN_TYPE null pointer constants to pointers.
gcc/testsuite/
* gcc.dg/c11-null-pointer-constant-1.c,
gcc.dg/c23-null-pointer-constant-1.c: New tests.
diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index 26ee0ebf91f0..a701dd090fb8 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -8457,6 +8457,8 @@ convert_for_assignment (location_t location, location_t
expr_loc, tree type,
}
else if (codel == POINTER_TYPE
&& (coder == INTEGER_TYPE
+ || coder == ENUMERAL_TYPE
+ || coder == BOOLEAN_TYPE
|| coder == NULLPTR_TYPE
|| coder == BITINT_TYPE))
{
diff --git a/gcc/testsuite/gcc.dg/c11-null-pointer-constant-1.c
b/gcc/testsuite/gcc.dg/c11-null-pointer-constant-1.c
new file mode 100644
index 000000000000..f463a1a59da3
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c11-null-pointer-constant-1.c
@@ -0,0 +1,55 @@
+/* Test zero with different types as null pointer constant: bug 112556. */
+/* { dg-do compile } */
+/* { dg-options "-std=c11 -pedantic-errors -Wno-pointer-compare" } */
+
+enum e { ZERO };
+
+void *p1 = 0;
+void *p2 = 0LL;
+void *p3 = (char) 0;
+void *p4 = 0UL;
+void *p5 = (_Bool) 0;
+void *p6 = (enum e) ZERO;
+
+void f (void *);
+
+void *
+g (void)
+{
+ p1 = 0;
+ p2 = 0LL;
+ p3 = (char) 0;
+ p4 = 0UL;
+ p5 = (_Bool) 0;
+ p6 = (enum e) ZERO;
+ f (0);
+ f (0ULL);
+ f (0L);
+ f ((char) 0);
+ f ((_Bool) 0);
+ f ((enum e) ZERO);
+ (1 ? p1 : 0);
+ (1 ? p1 : 0L);
+ (1 ? p1 : 0ULL);
+ (1 ? p1 : (char) 0);
+ (1 ? p1 : (_Bool) 0);
+ (1 ? p1 : (enum e) 0);
+ p1 == 0;
+ p1 == 0LL;
+ p1 == 0U;
+ p1 == (char) 0;
+ p1 == (_Bool) 0;
+ p1 == (enum e) 0;
+ p1 != 0;
+ p1 != 0LL;
+ p1 != 0U;
+ p1 != (char) 0;
+ p1 != (_Bool) 0;
+ p1 != (enum e) 0;
+ return 0;
+ return 0UL;
+ return 0LL;
+ return (char) 0;
+ return (_Bool) 0;
+ return (enum e) 0;
+}
diff --git a/gcc/testsuite/gcc.dg/c23-null-pointer-constant-1.c
b/gcc/testsuite/gcc.dg/c23-null-pointer-constant-1.c
new file mode 100644
index 000000000000..71b66cc35d6b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c23-null-pointer-constant-1.c
@@ -0,0 +1,120 @@
+/* Test zero with different types as null pointer constant: bug 112556. */
+/* { dg-do compile } */
+/* { dg-options "-std=c23 -pedantic-errors -Wno-pointer-compare" } */
+
+enum e { ZERO };
+enum e2 : bool { BZERO };
+enum e3 : long { LZERO };
+
+void *p1 = 0;
+void *p2 = 0LL;
+void *p3 = (char) 0;
+void *p4 = 0UL;
+void *p5 = (bool) 0;
+void *p6 = (enum e) ZERO;
+void *p7 = false;
+void *p8 = BZERO;
+void *p9 = (enum e2) 0;
+void *p10 = LZERO;
+void *p11 = (enum e3) 0;
+#ifdef __BITINT_MAXWIDTH__
+void *p12 = 0wb;
+void *p13 = 0uwb;
+#endif
+
+void f (void *);
+
+void *
+g (void)
+{
+ p1 = 0;
+ p2 = 0LL;
+ p3 = (char) 0;
+ p4 = 0UL;
+ p5 = (bool) 0;
+ p6 = (enum e) ZERO;
+ p7 = false;
+ p8 = BZERO;
+ p9 = (enum e2) 0;
+ p10 = LZERO;
+ p11 = (enum e3) 0;
+#ifdef __BITINT_MAXWIDTH__
+ p12 = 0wb;
+ p13 = 0uwb;
+#endif
+ f (0);
+ f (0ULL);
+ f (0L);
+ f ((char) 0);
+ f ((bool) 0);
+ f ((enum e) ZERO);
+ f (false);
+ f (BZERO);
+ f ((enum e2) 0);
+ f (LZERO);
+ f ((enum e3) 0);
+#ifdef __BITINT_MAXWIDTH__
+ f (0wb);
+ f (0uwb);
+#endif
+ (1 ? p1 : 0);
+ (1 ? p1 : 0L);
+ (1 ? p1 : 0ULL);
+ (1 ? p1 : (char) 0);
+ (1 ? p1 : (bool) 0);
+ (1 ? p1 : (enum e) 0);
+ (1 ? p1 : false);
+ (1 ? p1 : BZERO);
+ (1 ? p1 : (enum e2) 0);
+ (1 ? p1 : LZERO);
+ (1 ? p1 : (enum e3) 0);
+#ifdef __BITINT_MAXWIDTH__
+ (1 ? p1 : 0wb);
+ (1 ? p1 : 0uwb);
+#endif
+ p1 == 0;
+ p1 == 0LL;
+ p1 == 0U;
+ p1 == (char) 0;
+ p1 == (bool) 0;
+ p1 == (enum e) 0;
+ p1 == false;
+ p1 == BZERO;
+ p1 == (enum e2) 0;
+ p1 == LZERO;
+ p1 == (enum e3) 0;
+#ifdef __BITINT_MAXWIDTH__
+ p1 == 0wb;
+ p1 == 0uwb;
+#endif
+ p1 != 0;
+ p1 != 0LL;
+ p1 != 0U;
+ p1 != (char) 0;
+ p1 != (bool) 0;
+ p1 != (enum e) 0;
+ p1 != false;
+ p1 != BZERO;
+ p1 != (enum e2) 0;
+ p1 != LZERO;
+ p1 != (enum e3) 0;
+#ifdef __BITINT_MAXWIDTH__
+ p1 != 0wb;
+ p1 != 0uwb;
+#endif
+ return 0;
+ return 0UL;
+ return 0LL;
+ return (char) 0;
+ return (bool) 0;
+ return (enum e) 0;
+ return false;
+ return BZERO;
+ return (enum e2) 0;
+ return LZERO;
+ return (enum e3) 0;
+#ifdef __BITINT_MAXWIDTH__
+ return 0wb;
+ return 0uwb;
+#endif
+}
--
Joseph S. Myers
josmy...@redhat.com
