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    A bit speculative (since this is a hammer looking for a nail), but perhaps alloca() would really outshine malloc() in a multithreaded environment because of the lock contention in the latter. But this is a real stretch since small arrays should just use a fixed size, and large arrays will probably need the heap anyway. Commented Mar 14, 2013 at 13:57
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    @chrisaycock Yes, very much hammer looking for a nail, but a hammer which actually exists (be it C99 VLA or the not-actually-in-any-standard alloca, which I think are basically same thing). But that multithreaded thing is good, editing question to include it! Commented Mar 14, 2013 at 14:06
  • One disadvantage of VLAs is that there's no mechanism for detecting an allocation failure; if there's not enough memory, the behavior is undefined. (The same is true for fixed-size arrays -- and for alloca().) Commented Mar 14, 2013 at 15:38
  • @KeithThompson Well, there's no guarantee that malloc/new detects allocation failure either, for example see Notes for Linux malloc man page (linux.die.net/man/3/malloc). Commented Mar 14, 2013 at 15:42
  • @hyde: And it's debatable whether Linux's malloc behavior conforms to the C standard. Commented Mar 14, 2013 at 18:53