I've been experiencing random JSC crashes in the 2.4 branch for quite some time.
I don't have a detailed list of steps to reproduce this, but it happens relatively often (several times per day) with e.g Facebook.
The backtraces are not really meaningful:
Program received signal SIGSEGV, Segmentation fault.
#1 0x0000000000000000 in ?? ()
After some testing it seems that reverting r159826 solves the problem:
I tested this with WebKitGTK+ 2.4.1 and I haven't been able to crash the browser since then.
I haven't checked whether this affects master or if it has been fixed there, otherwise I propose that we revert that change in the stable branch.
Reverted in 2.4 branch in r168261. Thanks!