GNU bug report logs - #30756
GCC >= 6 '-isystem' and C_INCLUDE_PATH behavior changed, breaking #include_next

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From: Mark H Weaver <mhw <at> netris.org>
To: ludo <at> gnu.org (Ludovic Courtès)
Cc: 30756 <at> debbugs.gnu.org, Giel van Schijndel <giel <at> mortis.eu>
Subject: bug#30756: gcc7 doesn't find stdlib.h
Date: Fri, 04 May 2018 17:36:27 -0400

ludo <at> gnu.org (Ludovic Courtès) writes:

> Mark H Weaver <mhw <at> netris.org> skribis:
>
>> On my own private branch, I worked around this problem by adding
>> "-idirafter <LIBC>/include" to CXXFLAGS, but of course it's not a proper
>> fix.  My workaround happens to be in Savannah on the
>> 'reproduce-bug-29774' branch:
>>
>>   https://git.savannah.gnu.org/cgit/guix.git/commit/?h=reproduce-bug-29774&id=87022e2666c5e68e865eb160a4bd8e9cdcc1a955
>
> Perhaps we could achieve the same effect by adding “-idirafter
> LIBC/include” to the default spec file, under ‘cpp_options’?
> (We’d achieve that by modifying the value of ‘cpp_options’ in
> gcc/gcc.c.)

I guess that it might be better to avoid using -idirafter and instead
pay attention to the order in which the normal include search paths are
populated, and in particular for LIBC to last, but maybe that would be
awkward to arrange, dunno.

       Mark

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