Reapply [VFS] Add 'overlay-relative' field to YAML files

This reapplies r261552.

The VFS overlay mapping between virtual paths and real paths is done through
the 'external-contents' entries in YAML files, which contains hardcoded paths
to the real files.

When a module compilation crashes, headers are dumped into <name>.cache/vfs
directory and are mapped via the <name>.cache/vfs/vfs.yaml. The script
generated for reproduction uses -ivfsoverlay pointing to file to gather the
mapping between virtual paths and files inside <name>.cache/vfs. Currently, we
are only capable of reproducing such crashes in the same machine as they
happen, because of the hardcoded paths in 'external-contents'.

To be able to reproduce a crash in another machine, this patch introduces a new
option in the VFS yaml file called 'overlay-relative'. When it's equal to
'true' it means that the provided path to the YAML file through the
-ivfsoverlay option should also be used to prefix the final path for every
'external-contents'.

Example, given the invocation snippet "... -ivfsoverlay
<name>.cache/vfs/vfs.yaml" and the following entry in the yaml file:

"overlay-relative": "true",
"roots": [
...
  "type": "directory",
  "name": "/usr/include",
  "contents": [
    {
      "type": "file",
      "name": "stdio.h",
      "external-contents": "/usr/include/stdio.h"
    },
...

Here, a file manager request for virtual "/usr/include/stdio.h", that will map
into real path "/<absolute_path_to>/<name>.cache/vfs/usr/include/stdio.h.

This is a useful feature for debugging module crashes in machines other than
the one where the error happened.

Differential Revision: http://reviews.llvm.org/D17457

rdar://problem/24499339

llvm-svn: 263748

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/unittests/Basic/VirtualFileSystemTest.cpp b/clang/unittests/Basic/VirtualFileSystemTest.cpp
index 9448ad4..d2f4a7d 100644
--- a/clang/unittests/Basic/VirtualFileSystemTest.cpp
+++ b/clang/unittests/Basic/VirtualFileSystemTest.cpp
@@ -662,7 +662,7 @@ public:
   getFromYAMLRawString(StringRef Content,
                        IntrusiveRefCntPtr<vfs::FileSystem> ExternalFS) {
     std::unique_ptr<MemoryBuffer> Buffer = MemoryBuffer::getMemBuffer(Content);
-    return getVFSFromYAML(std::move(Buffer), CountingDiagHandler, this,
+    return getVFSFromYAML(std::move(Buffer), CountingDiagHandler, "", this,
                           ExternalFS);
   }