I've seen the wiki but this is the first time i use gdb so i do things without necessarily understanding.
I just saw i forgot to create the ~/.gdbinit file. With this file, the backtrace seems much smaller :
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fee1f8cb7e0 (LWP 18400)]
0x0000000000464f63 in CUpDownClient::ClearDownloadBlockRequests (this=0x41a3490)
at ../../src/BaseClient.cpp:1177
1177 in ../../src/BaseClient.cpp