In our project, there is a shared object with a reference counter, which will be increased if others acquire it and decreased if released. Once the reference counter is 0, the shared object can be reaped. Then we found the classical memory leak issue, i.e., the memory of shared object keeps growing. To debug this issue, I used libunwind.
The principle is simple: print the stack traces of every increment/decrement operations. I borrowed code from Programmatic access to the call stack in C++, and did some tweaks: mostly format the stack traces and output to file. The output is like this:
$ cat /tmp/backtrace.log
0x55ad59ec2556: (foo+0x9)
0x55ad59ec2562: (bar+0x9)
0x55ad59ec2579: (main+0x14)
0x7f941161ee0a: (__libc_start_main+0xea)
0x55ad59ec214a: (_start+0x2a)
A quick method to know the specific position in source code is through gdb: attach the program, then use “info line” command:
$ gdb program -p pid
......
(gdb) info line *0x55ad59ec2556
......
P.S., the code can be download here.