pass the reason for failure up from MemoryBuffer and report it

in diagnostics when we fail to open a file.  This allows us to
report things like:

$ clang test.c -I.
test.c:2:10: fatal error: error opening file './foo.h': Permission denied
#include "foo.h"
         ^

llvm-svn: 90276

2 files changed, 7 insertions, 4 deletions

diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index 9caca339be3..028593f39c7 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -1112,9 +1112,10 @@ void Preprocessor::HandleIncludeDirective(Token &IncludeTok,
   }
 
   // Finally, if all is good, enter the new file!
-  if (EnterSourceFile(FID, CurDir))
+  std::string ErrorStr;
+  if (EnterSourceFile(FID, CurDir, &ErrorStr))
     Diag(FilenameTok, diag::err_pp_error_opening_file)
-      << std::string(SourceMgr.getFileEntryForID(FID)->getName());
+      << std::string(SourceMgr.getFileEntryForID(FID)->getName()) << ErrorStr;
 }
 
 /// HandleIncludeNextDirective - Implements #include_next.
diff --git a/clang/lib/Lex/PPLexerChange.cpp b/clang/lib/Lex/PPLexerChange.cpp
index 8a61d7b9c24..1580b87dac6 100644
--- a/clang/lib/Lex/PPLexerChange.cpp
+++ b/clang/lib/Lex/PPLexerChange.cpp
@@ -64,7 +64,8 @@ PreprocessorLexer *Preprocessor::getCurrentFileLexer() const {
 
 /// EnterSourceFile - Add a source file to the top of the include stack and
 /// start lexing tokens from it instead of the current buffer.
-bool Preprocessor::EnterSourceFile(FileID FID, const DirectoryLookup *CurDir) {
+bool Preprocessor::EnterSourceFile(FileID FID, const DirectoryLookup *CurDir,
+                                   std::string *ErrorStr) {
   assert(CurTokenLexer == 0 && "Cannot #include a file inside a macro!");
   ++NumEnteredSourceFiles;
 
@@ -79,7 +80,8 @@ bool Preprocessor::EnterSourceFile(FileID FID, const DirectoryLookup *CurDir) {
   }
   
   // Get the MemoryBuffer for this FID, if it fails, we fail.
-  const llvm::MemoryBuffer *InputFile = getSourceManager().getBuffer(FID);
+  const llvm::MemoryBuffer *InputFile =
+    getSourceManager().getBuffer(FID, ErrorStr);
   if (InputFile == 0)
     return true;