[PATCH] D47894: [clang]: Add support for "-fno-delete-null-pointer-checks"

[Stephen Hines via Phabricator via cfe-commits]

srhines added a comment.

In https://reviews.llvm.org/D47894#1125728, @jyknight wrote:

> In https://reviews.llvm.org/D47894#1125653, @efriedma wrote:
>
> > The problem would come from propagating nonnull-ness from something which isn't inherently nonnull.  For example, strlen has a nonnull argument, so `strlen(NULL)` is UB, therefore given `int z = strlen(x); if (x) {...}`, we can remove the null check.  (Not sure we actually do this transform at the moment, but it's something we could do in the future.)
>
>
> I think the question there is actually whether we need to, in addition to supporting null pointer dereference, also cause all `__attribute__((nonnull))` annotations at the C/C++ level to be ignored.
>
> And, yes, I believe we should.


Is that what the kernel community actually wants though? There are certainly others who want a way to strip `__attribute__((nonnull))` completely, which seems a bit orthogonal to the removal of null checks in general. I think it would be good to support such a flag, but the presence of `nonnull` inside kernel sources leads me to believe they want those cases to be treated specially.


Repository:
  rC Clang

https://reviews.llvm.org/D47894