Re: [PATCH] libcpp: suppress builtin macro redefined warnings for __LINE__

[Longjun Luo <luolongjuna@gmail.com>]

On 12/2/2022 3:07 AM, Joseph Myers wrote:
> On Fri, 2 Dec 2022, Longjun Luo via Gcc-patches wrote:
>
>> On 12/2/2022 1:01 AM, Joseph Myers wrote:
>>> On Thu, 1 Dec 2022, Longjun Luo via Gcc-patches wrote:
>>>
>>>> diff --git a/gcc/testsuite/gcc.dg/builtin-redefine.c
>>>> b/gcc/testsuite/gcc.dg/builtin-redefine.c
>>>> index 882b2210992..9d5b42252ee 100644
>>>> --- a/gcc/testsuite/gcc.dg/builtin-redefine.c
>>>> +++ b/gcc/testsuite/gcc.dg/builtin-redefine.c
>>>> @@ -71,7 +71,6 @@
>>>>    /* { dg-bogus "Expected built-in is not defined" "" { target *-*-* } .-1
>>>> } */
>>>>    #endif
>>>>    -#define __LINE__ 0           /* { dg-warning "-:\"__LINE__\" redef" }
>>>> */
>>>>    #define __INCLUDE_LEVEL__ 0  /* { dg-warning "-:\"__INCLUDE_LEVEL__\"
>>>> redef" } */
>>>>    #define __COUNTER__ 0        /* { dg-warning "-:\"__COUNTER__\" redef" }
>>>> */
>>> Is there some existing test that verifies that this redefinition is still
>>> diagnosed by default (in the absence of -Wno-builtin-macro-redefined)?
>> I am not sure I have fully understood your meaning. The problem here is that
>> if I try to redefine __LINE__ macro in the situation that projects use the
>> option '-Werror', the compile will fail.
> There are two cases:
>
> (a) Is redefinition of __LINE__ diagnosed *without*
> -Wno-builtin-macro-redefined?
>
> (b) Is redefinition of __LINE__ diagnosed *with*
> -Wno-builtin-macro-redefined?
>
> My understanding is that both (a) and (b) have answer "yes" at present,
> and your patch would change the answer to (b) to "no", without changing
> the answer to (a).
>
> My question is about whether there is a test verifying the answer to (a).
> If not, I think the patch should add one.


After some check for the source code, two similiar exist test cases for 
the situation (a).

They are ./gcc/testsuite/gcc.dg/cpp/warn-redefined.c and 
./gcc/testsuite/gcc.dg/cpp/warn-redefined-2.c

These two cases redefine the __TIME__ macro when using the option 
'-Wbuiltin-macro-redefined'.

I think I shoud add a test to verify __LINE__ macro in these two cases.

I will write a complete test for situation (a) and situation (b). But I 
need a little time to be familar with the gcc testcases.

So, the patch itself has no problem. What I need do is to rich its test 
cases and update change log, right?