bug#36882: Qemu 4.2.0 build for x86_64-linux fails

["Ludovic Courtès" <ludo@gnu.org>]

Hi,

Mathieu Othacehe <m.othacehe@gmail.com> skribis:

>> So is it expected that C_INCLUDE_PATH comes before the hard-coded GCC
>> include directory?  How can we work around that?
>
> Turns out, the best source of documentation here is
> gcc/incpath.c. Here's a summary of my understanding.
>
> Header search list:
>
> * QUOTE
>  -> -iquote 
> * BRACKET
>  -> -I goes here
>  -> CPATH goes here
> * SYSTEM
>  -> -isystem goes here
>  -> C_INCLUDE_PATH goes here
>  -> Hardcoded includes (gcc + glibc) goes here
> * AFTER
> -> -idirafter goes here.
>
> Duplicates inside SYSTEM are deleted, the first occurence is kept. So as
> long as we have glibc in C_INCLUDE_PATH it will trigger deletion of
> glibc in hardcoded includes and AFTER section.
>
> So I can see only two solutions here.
>
> 1. Go back to using CPATH (sad!), because when there is duplication
> between BRACKET and SYSTEM, the include from SYSTEM is kept (why it
> works on master).
>
> 2. Find a way to remove glibc from C_INCLUDE_PATH, but I have no clue
> how to do this properly. Maybe using some kind of filter on
> search-path-specifications.

I’d rather go for #2.  To do that, we could modify the ‘set-paths’ phase
to manually remove glibc from C_INCLUDE_PATH (fragile), or we could
modify GCC (perhaps removing the ‘remove_duplicates’ call for SYSTEM).

Either way, this wouldn’t work well with ‘guix environment’, where glibc
ends up in /gnu/store/…-profile, so it does not appear as duplicate to
GCC.

On ‘core-updates’, I see:

--8<---------------cut here---------------start------------->8---
$ git log | head -3
commit 5afcb5caa53615c0a432e0c1781155398d747218
Author: Ludovic Courtès <ludo@gnu.org>
Date:   Sat Feb 22 21:39:27 2020 +0100
$ ./pre-inst-env guix environment -C -e '(@@ (gnu packages commencement) coreutils-final)'
[env]$ gcc -v -x c -E /dev/null
Using built-in specs.
COLLECT_GCC=gcc
Target: x86_64-unknown-linux-gnu
Configured with: 
Thread model: posix
gcc version 7.5.0 (GCC) 
COLLECT_GCC_OPTIONS='-v' '-E' '-mtune=generic' '-march=x86-64'
 /gnu/store/0pjrnr8vhp94ykvarysd9wg7hcvfqkl5-gcc-7.5.0/libexec/gcc/x86_64-unknown-linux-gnu/7.5.0/cc1 -E -quiet -v /dev/null -mtune=generic -march=x86-64
ignoring duplicate directory "/gnu/store/k9l4v4530p1a69j8qs0aijbmn8lwak20-profile/include"
ignoring nonexistent directory "/no-gcc-local-prefix/include"
ignoring nonexistent directory "/gnu/store/adrw71v03nawqwyblxc0mdhcc41j5vnn-gcc-7.5.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.5.0/../../../../../../../x86_64-unknown-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /gnu/store/k9l4v4530p1a69j8qs0aijbmn8lwak20-profile/include
 /gnu/store/adrw71v03nawqwyblxc0mdhcc41j5vnn-gcc-7.5.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.5.0/include
 /gnu/store/adrw71v03nawqwyblxc0mdhcc41j5vnn-gcc-7.5.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.5.0/include-fixed
 /gnu/store/ccjj5wg0qkjs1zfjr98nhb8cpr434izw-glibc-2.31/include
End of search list.
# 1 "/dev/null"
# 1 "<built-in>"
# 1 "<command-line>"
# 31 "<command-line>"
# 1 "/gnu/store/k9l4v4530p1a69j8qs0aijbmn8lwak20-profile/include/stdc-predef.h" 1 3
# 32 "<command-line>" 2
# 1 "/dev/null"
COMPILER_PATH=/gnu/store/0pjrnr8vhp94ykvarysd9wg7hcvfqkl5-gcc-7.5.0/libexec/gcc/x86_64-unknown-linux-gnu/7.5.0/:/gnu/store/0pjrnr8vhp94ykvarysd9wg7hcvfqkl5-gcc-7.5.0/libexec/gcc/x86_64-unknown-linux-gnu/7.5.0/:/gnu/store/0pjrnr8vhp94ykvarysd9wg7hcvfqkl5-gcc-7.5.0/libexec/gcc/x86_64-unknown-linux-gnu/:/gnu/store/adrw71v03nawqwyblxc0mdhcc41j5vnn-gcc-7.5.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.5.0/:/gnu/store/adrw71v03nawqwyblxc0mdhcc41j5vnn-gcc-7.5.0-lib/lib/gcc/x86_64-unknown-linux-gnu/
LIBRARY_PATH=/gnu/store/k9l4v4530p1a69j8qs0aijbmn8lwak20-profile/lib/:/gnu/store/k9l4v4530p1a69j8qs0aijbmn8lwak20-profile/lib/:/gnu/store/adrw71v03nawqwyblxc0mdhcc41j5vnn-gcc-7.5.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.5.0/:/gnu/store/adrw71v03nawqwyblxc0mdhcc41j5vnn-gcc-7.5.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.5.0/../../../:/gnu/store/ccjj5wg0qkjs1zfjr98nhb8cpr434izw-glibc-2.31/lib
COLLECT_GCC_OPTIONS='-v' '-E' '-mtune=generic' '-march=x86-64'
--8<---------------cut here---------------end--------------->8---

Looking at ‘cppdefault.c’ in GCC, I don’t see where glibc-2.31/include
comes from; it seems that ‘INCLUDE_DEFAULTS’ is undefined on glibc
systems.

Thoughts?

Incidentally, do we have problems building anything other than QEMU?

Thanks,
Ludo’.