[PATCH RFA] libstdc++: avoid __GLIBCXX__ redefinition

[Jason Merrill]

On 8/28/24 6:22 AM, Jason Merrill wrote:
> On 8/28/24 6:09 AM, Jonathan Wakely wrote:
>> On Wed, 28 Aug 2024 at 10:58, Jason Merrill <jason@redhat.com> wrote:
>>>
>>> On 8/28/24 5:55 AM, Jonathan Wakely wrote:
>>>> On Wed, 28 Aug 2024 at 10:54, Jason Merrill wrote:
>>>>>
>>>>> Tested x86_64-pc-linux-gnu, OK for trunk?
>>>>
>>>> Redefining that macro to invalidate PCH is a bit of a hack, but it's
>>>> what we have for now, so OK for trunk, thanks.
>>>
>>> If it's just to invalidate PCH, do we want to #undef instead?
>>
>> It might not even be necessary now, since r14-3276-g91315f23ba127e
>> removed any -include bits/stdc++.h from the flags. I'd need to look
>> into that though.
> 
> I suppose it could still find some random other PCH corresponding to the 
> first #include, though that seems very unlikely.
> 
>>>   Does
>>> anything care about the actual value of the macro?
>>
>> No, I don't think so.
>>
>> But #undef would only work if it comes after including
>> <bits/c++config.h>, so we'd need to force an include of that into the
>> flags.
> 
> I meant #undef before #define in c++config.h so we get the normal value.

Like so.  Do you prefer this or the original patch?


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