manmanren added a comment.
In https://reviews.llvm.org/D25916#594844, @benlangmuir wrote:
> > Does it mean that a system module should only import system modules? If a
> > system module is allowed to import non-system modules, for a non-system
> > module, we will validate diagnostic options differently depending on
> > whether a system module or a non-system module imports it. This will cause
> > a non-system module that was validated earlier to be invalidated by a child
> > thread.
>
> It seems like we should validate the options the same way regardless of what
> the importer is, but I'm guessing this was done for a reason... What's the
> behaviour of a user-header imported by a system header (without modules)? If
> the user header warnings show up even without -Wsystem-headers, then we
> should be okay validating, right?
I tried a simple example:
cat test.mm
#include "a.h"
cat Inputs/System/a.h
#include "b.h"
cat Inputs/b.h
void double_declarator1(int *_Nonnull *); // expected-warning{{pointer is
missing a nullability type specifier (_Nonnull, _Nullable, or
_Null_unspecified)}}
clang -cc1 -fsyntax-only -fblocks -I Inputs/ -isystem Inputs/System/ test.mm
--> has no warning
~/llvm_gmail/debug/bin/clang -cc1 -fsyntax-only -fblocks -I Inputs/ -isystem
Inputs/System/ test.mm -Wsystem-headers
--> has one warning
Without modules, the user header warnings do not show up if it is included by a
system header (without -Wsystem-headers). To exactly match this behavior, user
modules need to be validated considering the importing context. We will need to
change the code snippets I mentioned earlier to re-validate the options when
the importing context changes.
Thanks,
Manman
https://reviews.llvm.org/D25916
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