jamieschmeiser added inline comments.
================
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}}
}
----------------
jamieschmeiser wrote:
> 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.
I disagree with the comment that the two warnings are not useful. While it is
the same warning, the section of code indicated by each warning is different
and both need to be corrected to clear the code of warnings. A single warning
would likely be more confusing in that a user would see the same warning and
not notice that a different section of code is indicated after fixing the
indicated problem. I would expect the typical response to be the user assuming
that they had made a mistake and removing the initial fix and fixing the
second, only to again receive a same warning again with a different section of
code. The different code sections indicated would likely be overlooked,
leading to frustration whereas two warnings clearly indicates there are 2
problems.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D98798/new/
https://reviews.llvm.org/D98798
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