[PATCH] D98798: Produce warning for performing pointer arithmetic on a null pointer.

[Jamie Schmeiser via Phabricator via cfe-commits]

jamieschmeiser added inline comments.


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Comment at: clang/test/Sema/pointer-addition.c:34
+  f = (char*)(f - (char*)0); // expected-warning {{performing pointer arithmetic on a null pointer has undefined behavior}}
+  f = (char*)((char*)0 - (char*)0); // expected-warning {{performing pointer arithmetic on a null pointer has undefined behavior}} expected-warning {{performing pointer arithmetic on a null pointer has undefined behavior}}
 }
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efriedma wrote:
> This is what I was afraid would happen.
> 
> C++ has a specific carveout in the standard that "null-null" isn't undefined. C doesn't, but I'm not sure warning is practically useful there.
> 
> In any case, printing the same warning twice isn't useful.
Yes, I see that [expr.add] p 7 says nullptr-nullptr is defined to be 0.  I will suppress the warning for this.


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  https://reviews.llvm.org/D98798/new/

https://reviews.llvm.org/D98798