The aplication throws SIGSEGV when run under gdb debuger.

[dembekadam]

We updated libprotobut to 23.4.0 that is using abls 2023_01_25.
Normally application works fine but when run under gdb it throws SIGSEGV.

0x00007f063124de52 in absl::lts_20230125::base_internal::LowLevelAlloc::Free(void*) ()
from /opt/3rd/lib64/libprotobuf.so.23.4.0
(gdb) bt
#0 0x00007f063124de52 in absl::lts_20230125::base_internal::LowLevelAlloc::Free(void*) ()
from /opt/3rd/lib64/libprotobuf.so.23.4.0
#1 0x00007f06311e1be0 in absl::lts_20230125::synchronization_internal::ReclaimThreadIdentity(void*) ()
from /opt/3rd/lib64/libprotobuf.so.23.4.0
#2 0x00007f062dc17451 in __nptl_deallocate_tsd () at pthread_create.c:301
#3 0x00007f062dc181eb in __nptl_deallocate_tsd () at pthread_create.c:256
#4 start_thread (arg=) at pthread_create.c:490

I have looked at ReclaimThreadIdentity and this is a destructor caled when thread ends to cleanup some data set by mutex.cc
// Called in debug mode when a thread is about to acquire a lock in a way that
// may block.
SynchLocksHeld *all_locks = Synch_GetAllLocks();

Do I understand it correctly that those locks are added only when run under gdb ? What is the purpose of this ?

Also the address calculation LowLevelAlloc::Free sems quire strange.

LowLevelAlloc::Free(void *v)
AllocList *f = reinterpret_cast<AllocList *>(
reinterpret_cast<char *>(v) - sizeof (f->header));

It refers to some address before passed *v. I suspect this is causing SIGSEGV

What is the reelection between AllocList structure used in LowLevelAlloc::Free and SynchLocksHeld *all_locks passed as *v ?

[derekmauro]

Do I understand it correctly that those locks are added only when run under gdb?

No.

It refers to some address before passed *v.

The raw allocation has metadata associated with it that comes before the address that gets handed out. The code calculates the real address to release.

[dembekadam]

The problem was cause by different thread writing to incorrect memory, not related to absl.