On 1/13/22 10:40 AM, Martin Liška wrote:
[...]
Apart from that, I support the patch (I cannot approve it). Note we're
now approaching
stage4 and this is definitelly a stage1 material (opens after GCC
12.1.0 gets released).
Thanks, Martin, I've updated the patch following your suggestions.
Cheers
Tomas
Cheers,
Martin
>From 4db4e6b35be5793902d8820d2c8e4d1f1cbba80d Mon Sep 17 00:00:00 2001
From: Tomas Kalibera <tomas.kalib...@gmail.com>
Date: Thu, 13 Jan 2022 05:25:32 -0500
Subject: [PATCH] c-family: Let stdio.h override built in printf format
[PR95130,PR92292]
Mingw32 targets use ms_printf format for printf, but mingw-w64 when
configured for UCRT uses gnu_format (via stdio.h). GCC then checks both
formats, which means that one cannot print a 64-bit integer without a
warning. All these lines issue a warning:
printf("Hello %"PRIu64"\n", x);
printf("Hello %I64u\n", x);
printf("Hello %llu\n", x);
because each of them violates one of the formats. Also, one gets a warning
twice if the format string violates both formats.
Fixed by disabling the built in format in case there are additional ones.
gcc/c-family/ChangeLog:
PR c/95130
PR c/92292
* c-common.c (check_function_arguments): Pass also function
declaration to check_function_format.
* c-common.h (check_function_format): Extra argument - function
declaration.
* c-format.c (check_function_format): For builtin functions with a
built in format and at least one more, do not check the first one.
---
gcc/c-family/c-common.c | 2 +-
gcc/c-family/c-common.h | 2 +-
gcc/c-family/c-format.c | 32 ++++++++++++++++++++++++++++++--
3 files changed, 32 insertions(+), 4 deletions(-)
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 4a6a4edb763..00fc734d28e 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -6064,7 +6064,7 @@ check_function_arguments (location_t loc, const_tree fndecl, const_tree fntype,
/* Check for errors in format strings. */
if (warn_format || warn_suggest_attribute_format)
- check_function_format (fntype, TYPE_ATTRIBUTES (fntype), nargs, argarray,
+ check_function_format (fndecl, fntype, TYPE_ATTRIBUTES (fntype), nargs, argarray,
arglocs);
if (warn_format)
diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index 8b7bf35e888..ee370eafbbc 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -856,7 +856,7 @@ extern void check_function_arguments_recurse (void (*)
unsigned HOST_WIDE_INT);
extern bool check_builtin_function_arguments (location_t, vec<location_t>,
tree, tree, int, tree *);
-extern void check_function_format (const_tree, tree, int, tree *,
+extern void check_function_format (const_tree, const_tree, tree, int, tree *,
vec<location_t> *);
extern bool attribute_fallthrough_p (tree);
extern tree handle_format_attribute (tree *, tree, tree, int, bool *);
diff --git a/gcc/c-family/c-format.c b/gcc/c-family/c-format.c
index afa77810a5c..bc2abee5146 100644
--- a/gcc/c-family/c-format.c
+++ b/gcc/c-family/c-format.c
@@ -1160,12 +1160,13 @@ decode_format_type (const char *s, bool *is_raw /* = NULL */)
attribute themselves. */
void
-check_function_format (const_tree fntype, tree attrs, int nargs,
+check_function_format (const_tree fndecl, const_tree fntype, tree attrs, int nargs,
tree *argarray, vec<location_t> *arglocs)
{
- tree a;
+ tree a, aa;
tree atname = get_identifier ("format");
+ bool skipped_default_format = false;
/* See if this function has any format attributes. */
for (a = attrs; a; a = TREE_CHAIN (a))
@@ -1176,6 +1177,33 @@ check_function_format (const_tree fntype, tree attrs, int nargs,
function_format_info info;
decode_format_attr (fntype, atname, TREE_VALUE (a), &info,
/*validated=*/true);
+
+ /* Mingw32 targets have traditionally used ms_printf format for the
+ printf function, and this format is built in GCC. But nowadays,
+ if mingw-w64 is configured to target UCRT, the printf function
+ uses the gnu_printf format (specified in the stdio.h header). This
+ causes GCC to check both formats, which means that there is no way
+ to e.g. print a long long unsigned without a warning (ms_printf
+ warns for %llu and gnu_printf warns for %I64u). Also, GCC would warn
+ twice about the same issue when both formats are violated, e.g.
+ for %lu used to print long long unsigned.
+
+ Hence, if there are multiple format specifiers, we skip the first
+ one. See PR 95130, PR 92292. */
+
+ if (!skipped_default_format && fndecl)
+ {
+ for(aa = TREE_CHAIN (a); aa; aa = TREE_CHAIN(aa))
+ if (is_attribute_p ("format", get_attribute_name (aa)) &&
+ fndecl && fndecl_built_in_p (fndecl, BUILT_IN_NORMAL))
+ {
+ skipped_default_format = true;
+ break;
+ }
+ if (skipped_default_format)
+ continue;
+ }
+
if (warn_format)
{
/* FIXME: Rewrite all the internal functions in this file
--
2.25.1
