[Preamble] Fix an undefined behavior when checking an empty preamble can be reused.
Summary: Passing nullptr to memcmp is UB.
Reviewers: ilya-biryukov
Reviewed By: ilya-biryukov
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D50967
llvm-svn: 340403
diff --git a/clang/lib/Frontend/PrecompiledPreamble.cpp b/clang/lib/Frontend/PrecompiledPreamble.cpp
index 4bff339..239e0dd 100644
--- a/clang/lib/Frontend/PrecompiledPreamble.cpp
+++ b/clang/lib/Frontend/PrecompiledPreamble.cpp
@@ -426,8 +426,8 @@
// new main file.
if (PreambleBytes.size() != Bounds.Size ||
PreambleEndsAtStartOfLine != Bounds.PreambleEndsAtStartOfLine ||
- memcmp(PreambleBytes.data(), MainFileBuffer->getBufferStart(),
- Bounds.Size) != 0)
+ !std::equal(PreambleBytes.begin(), PreambleBytes.end(),
+ MainFileBuffer->getBuffer().begin()))
return false;
// The preamble has not changed. We may be able to re-use the precompiled
// preamble.