Segfault in bbcov on gcc-4.6

_From [peter.goodman](https://code.google.com/u/peter.goodman/) on October 07, 2013 17:39:57_

What steps will reproduce the problem? 1. Run bbcov on gcc (e.g. gcc-4.6). What is the expected output? What do you see instead? Expected output is that DR does not report a SEGFAULT. I see a SEGFAULT.

What happens:
gcc does a vfork, and the child process (sharing the parent process address space) does an execve with cc1. Right before the execve, bbcov's pre_syscall_event clears all memory, which is shared with the parent. After the execve finishes, the parent resumes and segfaults because its global data structures were destroyed.

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=1288_