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Re: [PATCH 11/13] Fix va_start related location

Gabriel Dos Reis <> writes:

> On Wed, Apr 25, 2012 at 10:20 AM, Dodji Seketeli <> wrote:
>> Gabriel Dos Reis <> writes:
>>> On Wed, Apr 25, 2012 at 9:04 AM, Dodji Seketeli <> wrote:
>>>> In gcc/testsuite/gcc.dg/pr30457.c, the first warning was not being
>>>> emitted because the relevant location was inside the var_start macro
>>>> defined in a system header. ÂIt can even point to a token for a
>>>> builtin macro there. ÂThis patch unwinds to the first token in real
>>>> source code in that case.
>>> While you are at it, could you also use a non-zero value for the second
>>> argument argument to warning_at?
>> I couldn't find any obvious value for it. ÂI am thinking maybe it would
>> make sense to introduction a new -Wva_start to warn about possible
>> dangerous uses of the va_start macro and use that as the second argument
>> for the relevant warnings emitted by fold_builtin_next_arg. ÂWhat do you
>> think?
> or -Wvarargs?

OK, I have cooked up a patch for this that I will send in a separate
thread shortly.

>> In any case, this topic seems logically unrelated to the purpose of
>> enable -ftrack-macro-expansion by default, so IMHO it would be better to
>> do this in a separate self contain patch. ÂAmong other things, this
>> would ease possible future back-ports. ÂWould you agree?
> OK.

While testing the separate patch, I realized that this one was missing
adjusting the location in another spot.  So I have updated this patch
accordingly.  The patch that adds -Wvarargs will come on top of it, and
will add some needed regression tests for the whole.

Tested on x86_64-unknown-linux-gnu against trunk.  Bootstrap is still
running ...

	* builtins.c (fold_builtin_next_arg): Unwinds to the first
	location in real source code.
 gcc/builtins.c |   23 +++++++++++++++++++----
 1 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/gcc/builtins.c b/gcc/builtins.c
index b47f218..5ddc47b 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -12095,6 +12095,13 @@ fold_builtin_next_arg (tree exp, bool va_start_p)
   tree fntype = TREE_TYPE (current_function_decl);
   int nargs = call_expr_nargs (exp);
   tree arg;
+  /* There is good chance the current input_location points inside the
+     definition of the va_start macro (perhaps on the token for
+     builtin) in a system header, so warnings will not be emitted.
+     Use the location in real source code.  */
+  source_location current_location =
+    linemap_unwind_to_first_non_reserved_loc (line_table, input_location,
+					      NULL);
   if (!stdarg_p (fntype))
@@ -12119,7 +12126,9 @@ fold_builtin_next_arg (tree exp, bool va_start_p)
 	  /* Evidently an out of date version of <stdarg.h>; can't validate
 	     va_start's second argument, but can still work as intended.  */
-	  warning (0, "%<__builtin_next_arg%> called without an argument");
+	  warning_at (current_location,
+		      0,
+		      "%<__builtin_next_arg%> called without an argument");
 	  return true;
       else if (nargs > 1)
@@ -12154,7 +12163,9 @@ fold_builtin_next_arg (tree exp, bool va_start_p)
 	     argument.  We just warn and set the arg to be the last
 	     argument so that we will get wrong-code because of
 	     it.  */
-	  warning (0, "second parameter of %<va_start%> not last named argument");
+	  warning_at (current_location,
+		      0,
+		      "second parameter of %<va_start%> not last named argument");
       /* Undefined by C99 (va_start):
@@ -12164,8 +12175,12 @@ fold_builtin_next_arg (tree exp, bool va_start_p)
          the default argument promotions, the behavior is undefined."
       else if (DECL_REGISTER (arg))
-        warning (0, "undefined behaviour when second parameter of "
-                 "%<va_start%> is declared with %<register%> storage");
+	{
+	  warning_at (current_location,
+		      0,
+		      "undefined behaviour when second parameter of "
+		      "%<va_start%> is declared with %<register%> storage");
+	}
       /* We want to verify the second parameter just once before the tree
 	 optimizers are run and then avoid keeping it in the tree,

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