llvm-cov: Slightly improved error checking.

- readInt() should check all 4 bytes can be read, not just 1.
- In the event of false data in the gcno file, it was possible to index
  into a non-existent index of SmallVector, causing assertion error.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194639 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 2 deletions

diff --git a/include/llvm/Support/GCOV.h b/include/llvm/Support/GCOV.h
index 469a9e3ef9..0aa716aac0 100644
--- a/include/llvm/Support/GCOV.h
+++ b/include/llvm/Support/GCOV.h
@@ -152,11 +152,11 @@ public:
   }
 
   bool readInt(uint32_t &Val) {
-    StringRef Str = Buffer->getBuffer().slice(Cursor, Cursor+4);
-    if (Str.empty()) {
+    if (Buffer->getBuffer().size() < Cursor+4) {
       errs() << "Unexpected end of memory buffer: " << Cursor+4 << ".\n";
       return false;
     }
+    StringRef Str = Buffer->getBuffer().slice(Cursor, Cursor+4);
     Cursor += 4;
     Val = *(const uint32_t *)(Str.data());
     return true;