Re: -Wformat-security warnings generated in gcc build

[Prathamesh Kulkarni <bilbotheelffriend@gmail.com>]

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On Thu, Jan 23, 2014 at 8:24 PM, Dodji Seketeli <dodji@redhat.com> wrote:
> Prathamesh Kulkarni <bilbotheelffriend@gmail.com> writes:
>
>>
>> Shall it be correct then to replace calls to error() and friends,
>> taking only format string with no-argument specifiers
>> to error_at_no_args() ? (similarly we shall need warning_at_no_args,
>> pedwarn_no_args, etc.)
>
> I would guess so, yes.
>
>>>
>>> Also, you'd need to modify cp/error.c:cp_printer in a similar way, to
>>> issue an internal_error each time we try to access a null test->args_ptr.
>>
>> Shall check for text->args_ptr be required in each case label of
>> argument specifier in pp_format()
>> and client-specific functions like cp_printer() ?
>
> Yes, I think so.  Maybe you can make that a bit more maintainable by
> creating a macro like those used to access text->args_ptr in cp_printer,
> e.g:
>
>     #define next_int     va_arg (*text->args_ptr, int)
>
> In that macro, make the check for text->args_ptr before accessing it,
> and then use that macro to access text->args_ptr through the function.
>

I was going through diagnostic.c, it appears that many functions in
(error(), error_at(), warning(), etc.) share common code (mostly
contains call to diagnostic_set_info() followed by call to
report_diagnostic()), which I guess can be re-written in terms of
emit_diagnostic(), however since it's variadic that's not possible. I
wrote a v_emit_diagnostic() function, that takes same arguments as
emit_diagnostic(), with additional va_list * at end (va_list * instead
of va_list, so I could pass NULL for error_no_args() and friends). Is
it correct to write these other functions (emit_diagnostic(), error(),
inform(), etc.) in terms of v_emit_diagnostic() ?





> --
>                 Dodji

[-- Attachment #2: diagnostic.patch --]
[-- Type: text/x-patch, Size: 5704 bytes --]

Index: diagnostic.c
===================================================================
--- diagnostic.c	(revision 206867)
+++ diagnostic.c	(working copy)
@@ -884,29 +884,38 @@ diagnostic_append_note (diagnostic_conte
   va_end (ap);
 }
 
-bool
-emit_diagnostic (diagnostic_t kind, location_t location, int opt,
-		 const char *gmsgid, ...)
+static bool
+v_emit_diagnostic (diagnostic_t kind, location_t location, int opt, const char *gmsgid, va_list *ap_p)
 {
   diagnostic_info diagnostic;
-  va_list ap;
   bool ret;
-
-  va_start (ap, gmsgid);
+  
   if (kind == DK_PERMERROR)
     {
-      diagnostic_set_info (&diagnostic, gmsgid, &ap, location,
+      diagnostic_set_info (&diagnostic, gmsgid, ap_p, location,
 			   permissive_error_kind (global_dc));
       diagnostic.option_index = permissive_error_option (global_dc);
     }
   else {
-      diagnostic_set_info (&diagnostic, gmsgid, &ap, location, kind);
+      diagnostic_set_info (&diagnostic, gmsgid, ap_p, location, kind);
       if (kind == DK_WARNING || kind == DK_PEDWARN)
 	diagnostic.option_index = opt;
   }
 
   ret = report_diagnostic (&diagnostic);
-  va_end (ap);
+  return ret;
+}
+
+bool
+emit_diagnostic (diagnostic_t kind, location_t location, int opt,
+		 const char *gmsgid, ...)
+{
+  va_list ap;
+  bool ret;
+
+  va_start (ap, gmsgid);
+  ret = v_emit_diagnostic (kind, location, opt, gmsgid, &ap);
+  va_end (ap); 
   return ret;
 }
 
@@ -915,12 +924,10 @@ emit_diagnostic (diagnostic_t kind, loca
 void
 inform (location_t location, const char *gmsgid, ...)
 {
-  diagnostic_info diagnostic;
   va_list ap;
 
   va_start (ap, gmsgid);
-  diagnostic_set_info (&diagnostic, gmsgid, &ap, location, DK_NOTE);
-  report_diagnostic (&diagnostic);
+  v_emit_diagnostic (DK_NOTE, location, 0, gmsgid, &ap);
   va_end (ap);
 }
 
@@ -947,15 +954,11 @@ inform_n (location_t location, int n, co
 bool
 warning (int opt, const char *gmsgid, ...)
 {
-  diagnostic_info diagnostic;
   va_list ap;
   bool ret;
 
   va_start (ap, gmsgid);
-  diagnostic_set_info (&diagnostic, gmsgid, &ap, input_location, DK_WARNING);
-  diagnostic.option_index = opt;
-
-  ret = report_diagnostic (&diagnostic);
+  ret = v_emit_diagnostic (DK_WARNING, input_location, opt, gmsgid, &ap);
   va_end (ap);
   return ret;
 }
@@ -967,14 +970,11 @@ warning (int opt, const char *gmsgid, ..
 bool
 warning_at (location_t location, int opt, const char *gmsgid, ...)
 {
-  diagnostic_info diagnostic;
   va_list ap;
   bool ret;
 
   va_start (ap, gmsgid);
-  diagnostic_set_info (&diagnostic, gmsgid, &ap, location, DK_WARNING);
-  diagnostic.option_index = opt;
-  ret = report_diagnostic (&diagnostic);
+  ret = emit_diagnostic (DK_WARNING, location, opt, gmsgid, &ap);
   va_end (ap);
   return ret;
 }
@@ -995,14 +995,11 @@ warning_at (location_t location, int opt
 bool
 pedwarn (location_t location, int opt, const char *gmsgid, ...)
 {
-  diagnostic_info diagnostic;
   va_list ap;
   bool ret;
 
   va_start (ap, gmsgid);
-  diagnostic_set_info (&diagnostic, gmsgid, &ap, location,  DK_PEDWARN);
-  diagnostic.option_index = opt;
-  ret = report_diagnostic (&diagnostic);
+  ret = v_emit_diagnostic (DK_PEDWARN, location, opt, gmsgid, &ap);
   va_end (ap);
   return ret;
 }
@@ -1017,15 +1014,11 @@ pedwarn (location_t location, int opt, c
 bool
 permerror (location_t location, const char *gmsgid, ...)
 {
-  diagnostic_info diagnostic;
   va_list ap;
   bool ret;
 
   va_start (ap, gmsgid);
-  diagnostic_set_info (&diagnostic, gmsgid, &ap, location,
-                       permissive_error_kind (global_dc));
-  diagnostic.option_index = permissive_error_option (global_dc);
-  ret = report_diagnostic (&diagnostic);
+  ret = v_emit_diagnostic (DK_PERMERROR, location, 0, gmsgid, &ap);
   va_end (ap);
   return ret;
 }
@@ -1035,12 +1028,10 @@ permerror (location_t location, const ch
 void
 error (const char *gmsgid, ...)
 {
-  diagnostic_info diagnostic;
   va_list ap;
 
   va_start (ap, gmsgid);
-  diagnostic_set_info (&diagnostic, gmsgid, &ap, input_location, DK_ERROR);
-  report_diagnostic (&diagnostic);
+  v_emit_diagnostic (DK_ERROR, input_location, 0, gmsgid, &ap);
   va_end (ap);
 }
 
@@ -1065,12 +1056,10 @@ error_n (location_t location, int n, con
 void
 error_at (location_t loc, const char *gmsgid, ...)
 {
-  diagnostic_info diagnostic;
   va_list ap;
 
   va_start (ap, gmsgid);
-  diagnostic_set_info (&diagnostic, gmsgid, &ap, loc, DK_ERROR);
-  report_diagnostic (&diagnostic);
+  v_emit_diagnostic (DK_ERROR, loc, 0, gmsgid, &ap); 
   va_end (ap);
 }
 
@@ -1080,12 +1069,10 @@ error_at (location_t loc, const char *gm
 void
 sorry (const char *gmsgid, ...)
 {
-  diagnostic_info diagnostic;
   va_list ap;
 
   va_start (ap, gmsgid);
-  diagnostic_set_info (&diagnostic, gmsgid, &ap, input_location, DK_SORRY);
-  report_diagnostic (&diagnostic);
+  v_emit_diagnostic (DK_SORRY, input_location, 0, gmsgid, &ap);
   va_end (ap);
 }
 
@@ -1103,12 +1090,10 @@ seen_error (void)
 void
 fatal_error (const char *gmsgid, ...)
 {
-  diagnostic_info diagnostic;
   va_list ap;
 
   va_start (ap, gmsgid);
-  diagnostic_set_info (&diagnostic, gmsgid, &ap, input_location, DK_FATAL);
-  report_diagnostic (&diagnostic);
+  v_emit_diagnostic (DK_FATAL, input_location, 0, gmsgid, &ap);
   va_end (ap);
 
   gcc_unreachable ();
@@ -1121,12 +1106,10 @@ fatal_error (const char *gmsgid, ...)
 void
 internal_error (const char *gmsgid, ...)
 {
-  diagnostic_info diagnostic;
   va_list ap;
 
   va_start (ap, gmsgid);
-  diagnostic_set_info (&diagnostic, gmsgid, &ap, input_location, DK_ICE);
-  report_diagnostic (&diagnostic);
+  v_emit_diagnostic (DK_ICE, input_location, 0, gmsgid, &ap);
   va_end (ap);
 
   gcc_unreachable ();