[libclang] Fix crash when a #pragma diagnostic is included in the preamble.

A PCH file keeps track of #pragma diagnostics state; when loading the preamble, they conflicted
with the #pragma diagnostic state already present in the DiagnosticsEngine object due to
parsing the preamble.

Fix this by clearing the state of the DiagnosticsEngine object.
Fixes rdar://10363572 && http://llvm.org/PR11254.

llvm-svn: 143644

1 files changed, 3 insertions, 7 deletions

diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
index 015e92dfcd7..0dd3a38da47 100644
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -1388,8 +1388,6 @@ llvm::MemoryBuffer *ASTUnit::getMainBufferWithPrecompiledPreamble(
 
         // Set the state of the diagnostic object to mimic its state
         // after parsing the preamble.
-        // FIXME: This won't catch any #pragma push warning changes that
-        // have occurred in the preamble.
         getDiagnostics().Reset();
         ProcessWarningOptions(getDiagnostics(), 
                               PreambleInvocation->getDiagnosticOpts());
@@ -1940,11 +1938,9 @@ bool ASTUnit::Reparse(RemappedFile *RemappedFiles, unsigned NumRemappedFiles) {
     OverrideMainBuffer = getMainBufferWithPrecompiledPreamble(*Invocation);
     
   // Clear out the diagnostics state.
-  if (!OverrideMainBuffer) {
-    getDiagnostics().Reset();
-    ProcessWarningOptions(getDiagnostics(), Invocation->getDiagnosticOpts());
-  }
-  
+  getDiagnostics().Reset();
+  ProcessWarningOptions(getDiagnostics(), Invocation->getDiagnosticOpts());
+
   // Parse the sources
   bool Result = Parse(OverrideMainBuffer);