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