Re: [PATCH] [12/11/10] Fix invalid format warnings on Windows

["Martin Liška" <mliska@suse.cz>]

On 1/12/22 14:34, Tomas Kalibera wrote:
> 
> On 1/11/22 2:37 PM, Martin Liška wrote:
>> Hello.
>>
>> I do support the patch, but I would ...
> 
> Thanks, Martin,  that makes the patch simpler and easier to maintain. Would the attached version do?
> 
> Thanks
> Tomas
> 
>>
>> On 1/7/22 19:33, Tomas Kalibera wrote:
>>> +          if (is_attribute_p ("format", get_attribute_name (aa)) &&
>>> +              fndecl && fndecl_built_in_p (fndecl, BUILT_IN_NORMAL))
>>> +            {
>>> +              switch (DECL_FUNCTION_CODE (fndecl))
>>> +            {
>>> +            case BUILT_IN_FSCANF:
>>> +            case BUILT_IN_PRINTF:
>>> +            case BUILT_IN_SCANF:
>>> +            case BUILT_IN_SNPRINTF:
>>> +            case BUILT_IN_SSCANF:
>>> +            case BUILT_IN_VFSCANF:
>>> +            case BUILT_IN_VPRINTF:
>>> +            case BUILT_IN_VSCANF:
>>> +            case BUILT_IN_VSNPRINTF:
>>> +            case BUILT_IN_VSSCANF:
>>> +            case BUILT_IN_DCGETTEXT:
>>> +            case BUILT_IN_DGETTEXT:
>>> +            case BUILT_IN_GETTEXT:
>>> +            case BUILT_IN_STRFMON:
>>> +            case BUILT_IN_STRFTIME:
>>> +            case BUILT_IN_SNPRINTF_CHK:
>>> +            case BUILT_IN_VSNPRINTF_CHK:
>>> +            case BUILT_IN_PRINTF_CHK:
>>> +            case BUILT_IN_VPRINTF_CHK:
>>> +              skipped_default_format = 1;
>>> +              break;
>>> +            default:
>>> +              break;
>>> +            }
>>> +            }
>>
>> ... skip this as the listed functions are only these that have defined ATTR_FORMAT_*:
>>
>> $ grep ATTR_FORMAT gcc/builtins.def
>> DEF_LIB_BUILTIN        (BUILT_IN_FSCANF, "fscanf", BT_FN_INT_FILEPTR_CONST_STRING_VAR, ATTR_FORMAT_SCANF_2_3)
>> DEF_LIB_BUILTIN        (BUILT_IN_PRINTF, "printf", BT_FN_INT_CONST_STRING_VAR, ATTR_FORMAT_PRINTF_1_2)
>> DEF_LIB_BUILTIN        (BUILT_IN_SCANF, "scanf", BT_FN_INT_CONST_STRING_VAR, ATTR_FORMAT_SCANF_1_2)
>> DEF_C99_BUILTIN        (BUILT_IN_SNPRINTF, "snprintf", BT_FN_INT_STRING_SIZE_CONST_STRING_VAR, ATTR_FORMAT_PRINTF_NOTHROW_3_4)
>> DEF_LIB_BUILTIN        (BUILT_IN_SSCANF, "sscanf", BT_FN_INT_CONST_STRING_CONST_STRING_VAR, ATTR_FORMAT_SCANF_NOTHROW_2_3)
>> DEF_C99_BUILTIN        (BUILT_IN_VFSCANF, "vfscanf", BT_FN_INT_FILEPTR_CONST_STRING_VALIST_ARG, ATTR_FORMAT_SCANF_2_0)
>> DEF_LIB_BUILTIN        (BUILT_IN_VPRINTF, "vprintf", BT_FN_INT_CONST_STRING_VALIST_ARG, ATTR_FORMAT_PRINTF_1_0)
>> DEF_C99_BUILTIN        (BUILT_IN_VSCANF, "vscanf", BT_FN_INT_CONST_STRING_VALIST_ARG, ATTR_FORMAT_SCANF_1_0)
>> DEF_C99_BUILTIN        (BUILT_IN_VSNPRINTF, "vsnprintf", BT_FN_INT_STRING_SIZE_CONST_STRING_VALIST_ARG, ATTR_FORMAT_PRINTF_NOTHROW_3_0)
>> DEF_C99_BUILTIN        (BUILT_IN_VSSCANF, "vsscanf", BT_FN_INT_CONST_STRING_CONST_STRING_VALIST_ARG, ATTR_FORMAT_SCANF_NOTHROW_2_0)
>> DEF_EXT_LIB_BUILTIN    (BUILT_IN_DCGETTEXT, "dcgettext", BT_FN_STRING_CONST_STRING_CONST_STRING_INT, ATTR_FORMAT_ARG_2)
>> DEF_EXT_LIB_BUILTIN    (BUILT_IN_DGETTEXT, "dgettext", BT_FN_STRING_CONST_STRING_CONST_STRING, ATTR_FORMAT_ARG_2)
>> DEF_EXT_LIB_BUILTIN    (BUILT_IN_GETTEXT, "gettext", BT_FN_STRING_CONST_STRING, ATTR_FORMAT_ARG_1)
>> DEF_EXT_LIB_BUILTIN    (BUILT_IN_STRFMON, "strfmon", BT_FN_SSIZE_STRING_SIZE_CONST_STRING_VAR, ATTR_FORMAT_STRFMON_NOTHROW_3_4)
>> DEF_LIB_BUILTIN        (BUILT_IN_STRFTIME, "strftime", BT_FN_SIZE_STRING_SIZE_CONST_STRING_CONST_TM_PTR, ATTR_FORMAT_STRFTIME_NOTHROW_3_0)
>> DEF_EXT_LIB_BUILTIN    (BUILT_IN_SNPRINTF_CHK, "__snprintf_chk", BT_FN_INT_STRING_SIZE_INT_SIZE_CONST_STRING_VAR, ATTR_FORMAT_PRINTF_NOTHROW_5_6)
>> DEF_EXT_LIB_BUILTIN    (BUILT_IN_VSNPRINTF_CHK, "__vsnprintf_chk", BT_FN_INT_STRING_SIZE_INT_SIZE_CONST_STRING_VALIST_ARG, ATTR_FORMAT_PRINTF_NOTHROW_5_0)
>> DEF_EXT_LIB_BUILTIN    (BUILT_IN_PRINTF_CHK, "__printf_chk", BT_FN_INT_INT_CONST_STRING_VAR, ATTR_FORMAT_PRINTF_2_3)
>> DEF_EXT_LIB_BUILTIN    (BUILT_IN_VPRINTF_CHK, "__vprintf_chk", BT_FN_INT_INT_CONST_STRING_VALIST_ARG, ATTR_FORMAT_PRINTF_2_0)
>>
>> Martin

Few inline comments:

> From 82a659c7e5b24bbd39ac567dff3f79cc4c1e083f Mon Sep 17 00:00:00 2001
> From: Tomas Kalibera <tomas.kalibera@gmail.com>
> Date: Wed, 12 Jan 2022 08:17:21 -0500
> Subject: [PATCH] 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:

Please shorted the commit message's first line and put the rest to next lines.

> 
>   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 | 31 +++++++++++++++++++++++++++++--
>  3 files changed, 31 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..da72d85f66e 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");
> +  int skipped_default_format = 0;

Use bool type: bool skipped_default_format = false;

>  
>    /* See if this function has any format attributes.  */
>    for (a = attrs; a; a = TREE_CHAIN (a))
> @@ -1176,6 +1177,32 @@ 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 = 1;
> +			break;
> +		  }
> +	      if (skipped_default_format) continue;

continue on next line please.

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).

Cheers,
Martin

> +	    }
> +
>  	  if (warn_format)
>  	    {
>  	      /* FIXME: Rewrite all the internal functions in this file
> -- 
> 2.25.1
>