Support relative paths in VFSFromYAML

Use llvm::sys::fs::make_absolute to get an absolute path before
matching. Also, allow "." directories to enable testing.  ".." is still
not supported, and will require crossing file system boundaries to
implement correctly.

llvm-svn: 202903

clang/lib/Basic/VirtualFileSystem.cpp

@@ -733,8 +733,12 @@ VFSFromYAML *VFSFromYAML::create(MemoryBuffer *Buffer,
 }
 
 ErrorOr<Entry *> VFSFromYAML::lookupPath(const Twine &Path_) {
-  SmallVector<char, 256> Storage;
-  StringRef Path = Path_.toNullTerminatedStringRef(Storage);
+  SmallString<256> Path;
+  Path_.toVector(Path);
+
+  // Handle relative paths
+  if (error_code EC = sys::fs::make_absolute(Path))
+    return EC;
 
   if (Path.empty())
     return error_code(errc::invalid_argument, system_category());
@@ -753,7 +757,10 @@ ErrorOr<Entry *> VFSFromYAML::lookupPath(const Twine &Path_) {
 ErrorOr<Entry *> VFSFromYAML::lookupPath(sys::path::const_iterator Start,
                                          sys::path::const_iterator End,
                                          Entry *From) {
-  // FIXME: handle . and ..
+  if (Start->equals("."))
+    ++Start;
+
+  // FIXME: handle ..
   if (CaseSensitive ? !Start->equals(From->getName())
                     : !Start->equals_lower(From->getName()))
     // failure to match

clang/test/VFS/relative-path.c

@@ -0,0 +1,11 @@
+// RUN: mkdir -p %t
+// RUN: cd %t
+// RUN: sed -e "s:INPUT_DIR:%S/Inputs:g" -e "s:OUT_DIR:%t:g" %S/Inputs/vfsoverlay.yaml > %t.yaml
+// RUN: %clang_cc1 -Werror -I . -ivfsoverlay %t.yaml -fsyntax-only %s
+// REQUIRES: shell
+
+#include "not_real.h"
+
+void foo() {
+  bar();
+}