MemoryBuffer: Add a missing error-check to getOpenFileImpl

Summary:
In case the function was called with a desired read size *and* the file
was not an "mmap()" candidate, the function was falling back to a
"pread()", but it was failing to check the result of that system call.
This meant that the function would return "success" even though the read
operation failed, and it returned a buffer full of uninitialized memory.

Reviewers: rnk, dblaikie

Subscribers: kristina, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66224

llvm-svn: 368977

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Support/MemoryBuffer.cpp b/llvm/lib/Support/MemoryBuffer.cpp
index d0e5bb154c1..2f31f059ddb 100644
--- a/llvm/lib/Support/MemoryBuffer.cpp
+++ b/llvm/lib/Support/MemoryBuffer.cpp
@@ -458,7 +458,9 @@ getOpenFileImpl(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
     return make_error_code(errc::not_enough_memory);
   }
 
-  sys::fs::readNativeFileSlice(FD, Buf->getBuffer(), Offset);
+  if (std::error_code EC =
+          sys::fs::readNativeFileSlice(FD, Buf->getBuffer(), Offset))
+    return EC;
 
   return std::move(Buf);
 }