On 11/01/16 16:20, Jason Merrill wrote:
> On 10/17/2016 03:18 PM, Bernd Edlinger wrote:
>> +@item -Wbuiltin-function-redefined @r{(C++ and Objective-C++ only)}
>> +@opindex Wbuiltin-function-redefined
>> +@opindex Wno-builtin-function-redefined
>> +Do warn if built-in functions are redefined. This option is only
>> +supported for C++ and Objective-C++. It is implied by @option{-Wall},
>> +which can be disabled with @option{-Wno-builtin-function-redefined}.
>
> There's no redefinition here (only a redeclaration), so perhaps
> -Wbuiltin-redeclaration-mismatch?
>
Works for me. Thanks.
> I'm not even sure we need a new warning. Can we combine this warning
> with the block that currently follows?
>
After 20 years of not having a warning on that,
an implicitly enabled warning would at least break lots of bogus
test cases. Of course in C we have an implicitly enabled warning,
so I would like to at least enable the warning on -Wall, thus
-Wshadow is too weak IMO.
>> else if ((DECL_EXTERN_C_P (newdecl)
>> && DECL_EXTERN_C_P (olddecl))
>> || compparms (TYPE_ARG_TYPES (TREE_TYPE (newdecl)),
>> TYPE_ARG_TYPES (TREE_TYPE (olddecl))))
>> {
>> /* A near match; override the builtin. */
>>
>> if (TREE_PUBLIC (newdecl))
>> warning_at (DECL_SOURCE_LOCATION (newdecl), 0,
>> "new declaration %q#D ambiguates built-in "
>> "declaration %q#D", newdecl, olddecl);
>> else
>> warning (OPT_Wshadow,
>> DECL_BUILT_IN (olddecl)
>> ? G_("shadowing built-in function %q#D")
>> : G_("shadowing library function %q#D"),
>> olddecl);
>> }
>
> It seems to me that if we have an extern "C" declaration that doesn't
> match the built-in, we should just warn.
>
> I looked at some of the testcases you mentioned in the bug report, and
> those declarations aren't extern "C", so we shouldn't be warning about
> them. Does your current patch still warn about those?
>
No. After looking at the false positives with the previous patch,
I changed my mind about that.
This started because I wanted to add builtin functions for some
special_function_p names. And I wanted to warn the user if he uses a
name that is recognized by special_function_p, but the parameters
don't match. Now I think we need to teach special_function_p to
distinguish "C" functions from "C++" functions, which it currently
cannot do, because that knowledge is only in the C++ FE.
Bernd.
