[PATCH] D53342: [SimplifyLibCalls] Mark known arguments with nonnull

Wed Aug 21 04:57:24 PDT 2019

xbolva00 added a comment.

It is still a UB and UBSanitizer warns. If somebody uses (typical combo) clang and gcc, one may be very surprised why debug/dev (with clang) builds work and release (with gcc) builds not.

While in 2014 or so there was no way to find this UB in codebases, we have now UB Sanitizer. In 2019 there is no excuse "it is a UB but it still kinda work (except gcc, ds9k,  ..)".  Add simple "if" - problem solved. For general case, anybody can send a paper to specify this behaviour to C committee.

Now, because of "memcpy(NULL, NULL, 0) fans" we cannot optimize null checks (imagine you have a wrappers above standard string functions..) - "no good reason". ?
I see a lot of opportunity from nonnull/dereferenceable annotation so I dont see why we should not to do it (ok, few codes may break - any sane codebase is checked by sanitizers anyway).

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D53342/new/

https://reviews.llvm.org/D53342