[Modules] Early-exit if ReadOptionsBlock fails to avoid crashing

If we didn't tell ReadOptionsBlock to allow failures then we can't
assume that the stream is not in the middle of a block if it returns
out-of-date. This was causing a crash when we tried to continue reading.

Also, it's just generally a good idea to early-exit if we're doing
implicit module builds, since we will want to immediately rebuild this
module anyway and there's no reason to waste time continuing after
failure.

rdar://problem/24114938

llvm-svn: 260563

1 files changed, 4 insertions, 3 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index b2f59d1fa6c..ac78da26140 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -2269,9 +2269,10 @@ ASTReader::ReadControlBlock(ModuleFile &F,
               (AllowConfigurationMismatch && Result == ConfigurationMismatch))
             Result = Success;
 
-          // If we've diagnosed a problem, we're done.
-          if (Result != Success &&
-              isDiagnosedResult(Result, ClientLoadCapabilities))
+          // If we can't load the module, exit early since we likely
+          // will rebuild the module anyway. The stream may be in the
+          // middle of a block.
+          if (Result != Success)
             return Result;
         } else if (Stream.SkipBlock()) {
           Error("malformed block record in AST file");