r212060 - Consider module depedencies when checking a preamble in libclang

[Ben Langmuir]

> On Jul 7, 2014, at 10:03 AM, Ben Langmuir <blangmuir at apple.com> wrote:
> 
>> 
>> On Jul 7, 2014, at 9:27 AM, Ulrich Weigand <Ulrich.Weigand at de.ibm.com> wrote:
>> 
>> 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?
> 
> I’ll fix the test to specify a unique module cache path.

r212467

> In general, we use llvm::sys::path::system_temp_dir to create the default module cache location.  On Darwin, we use DARWIN_USER_CACHE_DIR, which is user-specific so this isn’t an issue.  On Linux, we seem to honour the environment variable TMPDIR, before falling back to /var/tmp. I don’t know if this is correct for Linux; perhaps you know of a better way?
> 
> Ben
> 
>> 
>> Bye,
>> Ulrich
> 
> 
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