aaron.ballman added a comment.
In D123627#3707635 <https://reviews.llvm.org/D123627#3707635>, @efriedma wrote:
> If the declaration we're redeclaring is a builtin, should the diagnostic be
> in the "-Wincompatible-library-redeclaration" warning group? With this
> patch, we treat redefinitions of builtins without a prototype differently
> from redefinitions with a prototype, for example:
>
> void acos() {} // error
> void acos(void) {} // warning
>
> Just ran into some code in Android which is using the first form.
Er, I keep going back and forth on it. My initial inclination is that this is
closing a hole where we would incorrectly decide that these function signatures
are compatible enough to merge together when that's not the case, so an error
is appropriate. But the same can be said for redeclaring a builtin with an
incorrect prototype rather than declaring it without any prototype. Given that
these builtins are declared for the user automagically, I think I come down on
this being a case we'd rather warn instead of err. It'd be weird to allow the
user to define `void printf(void) {}` but not `void printf();` (except in C2x
mode).
If we make a change here, I think it'd be good to get it done for Clang 15. I'm
not certain I've got the bandwidth to make this change in that timeframe though
(I can hopefully start on this sometime this week, but I have prior commitments
with deadlines that take priority).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D123627/new/
https://reviews.llvm.org/D123627
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