[PATCH] Implement variable-sized alloca instrumentation (take 2).

[Yury Gribov]

> I did not give much thought to dynamic allocas, but what if we simply replace them with run-time calls somehow?


We could hide Max's linked lists behind an internal API, something like

  // Poison redzones and store metadata for new_alloca
  void asan_poison_alloca(uptr new_alloca, uptr size, uptr prev_alloca);
  
  // Unpoison all allocas below bound
  uptr asan_unpoison_allocas(uptr prev_alloca, uptr bound);

The ugly bound parameter is necessary to model the equally ugly alloca/VLA interwork. From https://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html :

  If you use both variable-length arrays and alloca in the same function, deallocation of a variable-length array also deallocates anything more recently allocated with alloca.


REPOSITORY
  rL LLVM

http://reviews.llvm.org/D7098

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