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

[Jeff Law <jeffreyalaw@gmail.com>]

On 4/30/23 12:30, Jeff Law wrote:
> 
> 
> On 1/12/23 09:02, Longjun Luo via Gcc-patches wrote:
>>  From 0821df518b264e754d698d399f98be1a62945e32 Mon Sep 17 00:00:00 2001
>> From: Longjun Luo <luolongjuna@gmail.com>
>> Date: Thu, 12 Jan 2023 23:59:54 +0800
>> Subject: [PATCH] libcpp: suppress builtin macro redefined warnings for
>>   __LINE__
>>
>> As implied in
>> gcc.gnu.org/legacy-ml/gcc-patches/2008-09/msg00076.html,
>> gcc provides -Wno-builtin-macro-redefined to suppress warning when
>> redefining builtin macro. However, at that time, there was no
>> scenario for __LINE__ macro.
>>
>> But, when we try to build a live-patch, we compare sections by using
>> -ffunction-sections. Some same functions are considered changed because
>> of __LINE__ macro.
>>
>> At present, to detect such a changed caused by __LINE__ macro, we
>> have to analyse code and maintain a function list. For example,
>> in kpatch, check this commit
>> github.com/dynup/kpatch/commit/0e1b95edeafa36edb7bcf11da6d1c00f76d7e03d.
>>
>> So, in this scenario, when we try to compared sections, it would
>> be better to support suppress builtin macro redefined warnings for
>> __LINE__ macro.
>>
>> Signed-off-by: Longjun Luo <luolongjuna@gmail.com>
>> ---
>>   gcc/testsuite/gcc.dg/builtin-redefine-1.c | 49 +++++++++++++++++++++++
>>   gcc/testsuite/gcc.dg/builtin-redefine.c   | 24 +++++++++--
>>   libcpp/init.cc                            |  2 +-
>>   3 files changed, 70 insertions(+), 5 deletions(-)
>>   create mode 100755 gcc/testsuite/gcc.dg/builtin-redefine-1.c
> Thanks.  I added a suitable ChangeLog and pushed this to the trunk.
This is causing regressions on various targets for a few tests:

lm32-sim: c-c++-common/cpp/pr92296-2.c  -Wc++-compat   (test for 
warnings, line 41)
lm32-sim: gcc.dg/cpp/undef2.c  (test for warnings, line 9)
lm32-sim: gcc.dg/cpp/undef2.c (test for excess errors)

I have reverted this patch from the trunk.  Please address the 
regressions and resubmit.

Thanks,
Jeff