[PATCH] D67986: [InstCombine] snprintf (d, size, "%s", s) -> memccpy (d, s, '\0', size - 1), d[size - 1] = 0

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In D67986#1692020 <https://reviews.llvm.org/D67986#1692020>, @efriedma wrote:

> Oh, hmm... actually, just realized something; is the new formulation actually equivalent?  Specifically, is it okay to write to "d[size - 1]" if the string is short?  Say, for example, you have something like `snprintf(buf, 10, "%s", "x")`.  That normally writes to two elements of the array: 0 and 1.  The rewritten version writes to three elements: 0, 1, and 9.


Sounds like this should be guarded to only work for simple (non-volatile, non-atomic) pointers?


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https://reviews.llvm.org/D67986