r307384 - [Frontend] Verify that the bitstream is not empty before reading

[Alex Lorenz via cfe-commits]

Author: arphaman
Date: Fri Jul  7 03:25:12 2017
New Revision: 307384

URL: http://llvm.org/viewvc/llvm-project?rev=307384&view=rev
Log:
[Frontend] Verify that the bitstream is not empty before reading
the serialised diagnostics

Clang should avoid calling report_fatal_error when the file with the serialised
diagnostics is empty. This commit changes Clang's serialised diagnostic reader,
now it reports an appropriate error instead of crashing.

rdar://31939877

Differential Revision: https://reviews.llvm.org/D35069

Added:
    cfe/trunk/test/Index/Inputs/empty.dia
    cfe/trunk/test/Index/read-empty-diags.test
Modified:
    cfe/trunk/lib/Frontend/SerializedDiagnosticReader.cpp

Modified: cfe/trunk/lib/Frontend/SerializedDiagnosticReader.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Frontend/SerializedDiagnosticReader.cpp?rev=307384&r1=307383&r2=307384&view=diff
==============================================================================
--- cfe/trunk/lib/Frontend/SerializedDiagnosticReader.cpp (original)
+++ cfe/trunk/lib/Frontend/SerializedDiagnosticReader.cpp Fri Jul  7 03:25:12 2017
@@ -27,6 +27,9 @@ std::error_code SerializedDiagnosticRead
   llvm::BitstreamCursor Stream(**Buffer);
   Optional<llvm::BitstreamBlockInfo> BlockInfo;
 
+  if (Stream.AtEndOfStream())
+    return SDError::InvalidSignature;
+
   // Sniff for the signature.
   if (Stream.Read(8) != 'D' ||
       Stream.Read(8) != 'I' ||

Added: cfe/trunk/test/Index/Inputs/empty.dia
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Index/Inputs/empty.dia?rev=307384&view=auto
==============================================================================
    (empty)

Added: cfe/trunk/test/Index/read-empty-diags.test
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Index/read-empty-diags.test?rev=307384&view=auto
==============================================================================
--- cfe/trunk/test/Index/read-empty-diags.test (added)
+++ cfe/trunk/test/Index/read-empty-diags.test Fri Jul  7 03:25:12 2017
@@ -0,0 +1,2 @@
+// RUN: not c-index-test -read-diagnostics %S/Inputs/empty.dia 2>&1 | FileCheck %s
+// CHECK: Trouble deserializing file (Invalid File): Invalid diagnostics signature