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

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: 261552

1 files changed, 2 insertions, 2 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index cf4b5cf20a1..feace7ec770 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -2344,8 +2344,8 @@ createVFSFromCompilerInvocation(const CompilerInvocation &CI,
       return IntrusiveRefCntPtr<vfs::FileSystem>();
     }
 
-    IntrusiveRefCntPtr<vfs::FileSystem> FS =
-        vfs::getVFSFromYAML(std::move(Buffer.get()), /*DiagHandler*/ nullptr);
+    IntrusiveRefCntPtr<vfs::FileSystem> FS = vfs::getVFSFromYAML(
+        std::move(Buffer.get()), /*DiagHandler*/ nullptr, File);
     if (!FS.get()) {
       Diags.Report(diag::err_invalid_vfs_overlay) << File;
       return IntrusiveRefCntPtr<vfs::FileSystem>();