Fixed a dependency issue of ThreadLocalPtr
Summary: When a child thread that uses ThreadLocalPtr, ThreadLocalPtr::OnThreadExit will be called when that child thread is destroyed. However, OnThreadExit will try to access a static singleton of ThreadLocalPtr, which will be destroyed when the main thread exit. As a result, when a child thread that uses ThreadLocalPtr exits AFTER the main thread exits, illegal memory access will occur. This diff includes a test that reproduce this legacy bug. ==2095206==ERROR: AddressSanitizer: heap-use-after-free on address 0x608000007fa0 at pc 0x959b79 bp 0x7f5fa7426b60 sp 0x7f5fa7426b58 READ of size 8 at 0x608000007fa0 thread T1 This patch fix this issue by having the thread local mutex never be deleted (but will leak small piece of memory at the end.) The patch also describe a better solution (thread_local) in the comment that requires gcc 4.8.1 and in latest clang as a future work once we agree to move toward gcc 4.8. Test Plan: COMPILE_WITH_ASAN=1 make thread_local_test -j32 ./thread_local_test --gtest_filter="*MainThreadDiesFirst" Reviewers: anthony, hermanlee4, sdong Reviewed By: sdong Subscribers: dhruba, leveldb Differential Revision: https://reviews.facebook.net/D53013
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