aaron.ballman added a comment.
In D122983#3484064 <https://reviews.llvm.org/D122983#3484064>, @manojgupta
wrote:
> We are finding a lot of failures in our ToT builds with this change. here is
> an example for a configure script:
>
> $ cat tent.c
> int main ()
> {
> tgetent(0,0);
> return 0;
> }
> $ bin/clang -c tent.c -Wno-error
> tent.c:3:2: error: call to undeclared function 'tgetent'; ISO C99 and later
> do not support implicit function declarations
> [-Wimplicit-function-declaration]
> tgetent(0,0);
> ^
> 1 error generated.
>
> It feels very surprising that Wno-error does not suppress this warning. Is
> that expected?
Yes and no. Warnings which default to an error have very surprising behavior
(at least to me) in terms of `-Werror` and `-w`. Specifying `-Wno-error`
doesn't downgrade these diagnostics into a warning
(https://godbolt.org/z/c43zTqTj1) and specifying `-w` doesn't disable the
warning (https://godbolt.org/z/Y8YYYecTd). As you can see, that behavior is not
specific to this patch but is just a general behavior with these kinds of
diagnostics. I also find the behavior surprising (in both cases), but the last
time I asked around about it, it sounded like this behavior was intentional for
some reasons. More exploration is needed to know whether we should make any
changes there.
In the meantime, `-Wno-error=implicit-function-declaration` should downgrade
the error to a warning for you (but as you noticed, you can't later re-upgrade
it into an error; so yes, these things behave a bit strangely IMO).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D122983/new/
https://reviews.llvm.org/D122983
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