On 18/04/16 20:32, Richard Smith wrote:
On Mon, Apr 18, 2016 at 6:28 AM, Vassil Vassilev <v.g.vassi...@gmail.com <mailto:v.g.vassi...@gmail.com>> wrote:

    On 08/04/16 03:24, Richard Smith via cfe-commits wrote:

        Author: rsmith
        Date: Thu Apr  7 20:23:59 2016
        New Revision: 265766

        URL: http://llvm.org/viewvc/llvm-project?rev=265766&view=rev
        Log:
        [modules] Add a comment to explain why -E leaves some
        #includes in the preprocessed output.

        Modified:
         cfe/trunk/lib/Frontend/PrintPreprocessedOutput.cpp
             cfe/trunk/test/Modules/preprocess.cpp

        Modified: cfe/trunk/lib/Frontend/PrintPreprocessedOutput.cpp
        URL:
        
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Frontend/PrintPreprocessedOutput.cpp?rev=265766&r1=265765&r2=265766&view=diff
        
==============================================================================
        --- cfe/trunk/lib/Frontend/PrintPreprocessedOutput.cpp (original)
        +++ cfe/trunk/lib/Frontend/PrintPreprocessedOutput.cpp Thu
        Apr  7 20:23:59 2016
        @@ -336,7 +336,9 @@ void PrintPPOutputPPCallbacks::Inclusion
                OS << "#include "
                   << (IsAngled ? '<' : '"')
                   << FileName
        -         << (IsAngled ? '>' : '"');
        +         << (IsAngled ? '>' : '"')
        +         << " /* clang -E: implicit import for module "
        +         << Imported->getFullModuleName() << " */";

    It seems that in some cases the FileName needs to be tweaked to be
    able to compile the output back. For instance:
    clang -I folder/ file.cxx
    cat file.cxx
    #include "subfolder/A.h"

    cat folder/subfolder/A.h
    #include "B.h"

    B.h resides in folder/subfolder/ and FileName argument would be
    B.h causing the printer to generate #include "B.h" /* clang -E:
    implicit import for... */ which cannot be compiled back.


Ugh, yeah, that makes sense.

It seems superficially that what we should do for a file found relative to the current file (or in MSVC mode, for a file found relative to a possibly-indirect includer of the current file) is to prepend the path from that file's search path to the current file. That is, if we find "foo/bar.h" in search path "includes/x", and we find "baz/quux.h" relative to bar.h, we should produce the path "foo/baz/quux.h" (to be found relative to "includes/x"). However, that won't work if there is a prior include path that also contains a "foo/baz/quux.h", so we would need to also include the search path in the include path. And *that* won't work if . is not a search path and one of the search paths is a relative path.
:( at first looked like an easy, nice solution, but apparently "twin peaks" killer phase is true again :)

I wonder whether the problem is really that we're handling #include search paths incorrectly in the presence of #line markers.
I am not sure I understand this. Could you give an example?
Perhaps for the relative path search we should somehow instruct clang to look for files relative to the presumed file rather than the physical file?
Could we detect that we are compiling a preprocessed file? I guess there are traces, eg. include stack push/pop values...
That would match our intent for these files. However, this doesn't match the GCC behavior, so we probably can't do it by default. =/

            }
              // Since we want a newline after the @import, but not a
        #<line>, start a new
              // line immediately.

        Modified: cfe/trunk/test/Modules/preprocess.cpp
        URL:
        
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/preprocess.cpp?rev=265766&r1=265765&r2=265766&view=diff
        
==============================================================================
        --- cfe/trunk/test/Modules/preprocess.cpp (original)
        +++ cfe/trunk/test/Modules/preprocess.cpp Thu Apr  7 20:23:59 2016
        @@ -1,6 +1,6 @@
          // RUN: rm -rf %t
          // RUN: %clang_cc1 -fmodules -fimplicit-module-maps
        -fmodules-cache-path=%t -I %S/Inputs -x c++ -E %s | \
        -// RUN:   FileCheck -strict-whitespace %s
        --check-prefix=CHECK --check-prefix=CXX
        +// RUN:   FileCheck -strict-whitespace %s
        --check-prefix=CHECK --check-prefix=CXX --check-prefix=CXX-DASHE
          // RUN: %clang_cc1 -fmodules -fimplicit-module-maps
        -fmodules-cache-path=%t -I %S/Inputs -x objective-c -E %s | \
          // RUN:   FileCheck -strict-whitespace %s
        --check-prefix=CHECK --check-prefix=OBJC
          // RUN: %clang_cc1 -fmodules -fimplicit-module-maps
        -fmodules-cache-path=%t -I %S/Inputs -x c++ -E
        -frewrite-includes %s | \
        @@ -14,7 +14,9 @@ foo bar baz
          // The weird {{ }} here is to prevent the -frewrite-includes
        test from matching its own CHECK lines.
            // CXX: #include{{ }}"dummy.h"
        +// CXX-DASHE-SAME: /* clang -E: implicit import for module
        dummy */
          // CXX: #include{{ }}"dummy.h"
        +// CXX-DASHE-SAME: /* clang -E: implicit import for module
        dummy */
          // CXX: foo bar baz
            // OBJC: @import{{ }}dummy; /* clang


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