r212060 - Consider module depedencies when checking a preamble in libclang

[Ulrich Weigand]

Ben Langmuir <blangmuir at apple.com> wrote on 07.07.2014 18:12:21:

> > And indeed running clang directly against the temporary files created
by
> > the test case I get:
> > uweigand at bns:~> ./llvm/build/llvm-head-debug/Debug+Asserts/bin/clang
> > -fmodules
-I /tmp/libclang-test-6a8ede /tmp/libclang-test-6a8ede/MFile.m
> > /tmp/libclang-test-6a8ede/MFile.m:2:25: error: variable has incomplete
type
> > 'struct Foo'
> > int main() { struct Foo foo; foo.bar = 7; foo.baz = 8; }
> >                        ^
> > /tmp/libclang-test-6a8ede/MFile.m:2:21: note: forward declaration of
> > 'struct Foo'
> > int main() { struct Foo foo; foo.bar = 7; foo.baz = 8; }
> >                    ^
> > 1 error generated.
>
> Could you try this again with the additional flags -Wmodule-build -
> Wauto-import as a sanity check that the module is being found?  It
> looks like the module isn’t being imported properly...

Hmm, interesting.  I get:

uweigand at bns:~> ./llvm/build/llvm-head-debug/Debug+Asserts/bin/clang
-fmodules -I /tmp/libclang-test-75f2f2 /tmp/libclang-test-75f2f2/MFile.m
-Wmodule-build -Wauto-import
/tmp/libclang-test-75f2f2/MFile.m:1:1: warning: treating #include as an
import of module 'A' [-Wauto-import]
#include "HeaderFile.h"
^~~~~~~~~~~~~~~~~~~~~~~
@import A;
/tmp/libclang-test-75f2f2/MFile.m:1:2: remark: building module 'A' as
'/var/tmp/org.llvm.clang/ModuleCache/1MXAFKYV64X0T/A-25ZFQ1VWL2WP7.pcm' [-Rmodule-build]

#include "HeaderFile.h"
 ^
/tmp/libclang-test-75f2f2/MFile.m:2:25: error: variable has incomplete type
'struct Foo'
int main() { struct Foo foo; foo.bar = 7; foo.baz = 8; }
                        ^
/tmp/libclang-test-75f2f2/MFile.m:2:21: note: forward declaration of
'struct Foo'
int main() { struct Foo foo; foo.bar = 7; foo.baz = 8; }
                    ^
1 warning and 1 error generated.

However, the really interesting fact is that afterwards,
there is no /var/tmp/org.llvm.clang/ModuleCache/1MXAFKYV64X0T
directory -- and there cannot be, because there is a
/var/tmp/org.llvm.clang/ModuleCache directory, owned
by another user on the system, and my user ID does not
have the privileges to create subdirectories there ...


After I've removed that directory, the test case now passes!
(But it will presumably fail for other users now ...)

How is this supposed to work on a multi-user machine?

Bye,
Ulrich