[Valgrind-developers] Bug 345928: Fix regtest threadname on amd64 / Fix problem with short stacks

[Matthias S. <zz...@ge...>]

Hi!

I analysed why the test memcheck/tests/threadname fails on amd64.

See also https://bugs.kde.org/show_bug.cgi?id=345928

On amd64 it has this on stderr:
==32123== Thread 2:
==32123== Invalid write of size 1
==32123==    at 0x40083F: bad_things (threadname.c:16)
==32123==  Address 0x53e71e2 is 0 bytes after a block of size 2 alloc'd
==32123==    at 0x4C28BEF: malloc (vg_replace_malloc.c:299)
==32123==    by 0x40082D: bad_things (threadname.c:15)
==32123==    by 0x40094E: child_fn_0 (threadname.c:61)
==32123==    by 0x4E3C203: start_thread (pthread_create.c:310)
==32123==

I then enabled debug and added more printf-statements:

The check "if (fp_min + 256 >= fp_max)" in coregrind/m_stacktrace.c:501
is triggered here.

By changing it to "if (fp_min + 128 >= fp_max)" it can be fixed.

I think amd64 is having problems here because some functions do not need
additional local variables but can use the redzone, so the stackframes
are small.

Regards
Matthias