FYI: s390x: Require GCC 7.1 or later to build glibc due to __builtin_add_overflow

[Stefan Liebler]

Hi gnulib-developers,

just as information, I've committed the glibc patch

"s390x: Require GCC 7.1 or later to build glibc."
http://sourceware.org/git/?p=glibc.git;a=commit;h=844b4d8b4b937fe6943d2c0c80ce7d871cdb1eb5

as if build with gcc 6.5.0, __builtin_add_overflow incorrectly detects
overflow on s390x.

Please find the link to gcc-Bug on the discussion on libc-alpha:

On 12/17/20 6:35 PM, Adhemerval Zanella wrote:
> On 15/12/2020 11:18, Stefan Liebler via Libc-alpha wrote:
>> GCC 6.5 fails to correctly build ldconfig with recent ld.so.cache
>> commits, e.g.:
>> 785969a047ad2f23f758901c6816422573544453
>> elf: Implement a string table for ldconfig, with tail merging
>>
>> If glibc is build with gcc 6.5.0:
>> __builtin_add_overflow is used in
>> <glibc>/elf/stringtable.c:stringtable_finalize()
>> which leads to ldconfig failing with "String table is too large".
>> This is also recognizable in following tests:
>> FAIL: elf/tst-glibc-hwcaps-cache
>> FAIL: elf/tst-glibc-hwcaps-prepend-cache
>> FAIL: elf/tst-ldconfig-X
>> FAIL: elf/tst-ldconfig-bad-aux-cache
>> FAIL: elf/tst-ldconfig-ld_so_conf-update
>> FAIL: elf/tst-stringtable
>>
>> See gcc "Bug 98269 - gcc 6.5.0 __builtin_add_overflow() with small
>> uint32_t values incorrectly detects overflow"
>> (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98269)
> 
> In any case, it would be good to alert gnulib developers about this
> potential issue.

Bye,
Stefan