[Object] Always initialized StartOfFile in Archive::Child::Child constructor.

Fixes uninitialized memory access revealed by https://reviews.llvm.org/D146534.

In empty archives, we use Child(nullptr,nullptr,nullptr) in Archive constructor in setFirstRegular. This copies unitialized StartOfFile to FirstRegularStartOfFile, which child_begin may use later.

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D148955

diff --git a/llvm/lib/Object/Archive.cpp b/llvm/lib/Object/Archive.cpp
index 6ddbe35..081ff79 100644 (file)
--- a/llvm/lib/Object/Archive.cpp
+++ b/llvm/lib/Object/Archive.cpp
@@ -468,6 +468,7 @@ Archive::Child::Child(const Archive *Parent, const char *Start, Error *Err)
     : Parent(Parent) {
   if (!Start) {
     Header = nullptr;
+    StartOfFile = -1;
     return;
   }