From 74ecc89c464a858f261ec279dd202dfafa476d7d Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <peter@pcc.me.uk>
Date: Fri, 19 Jun 2015 22:40:05 +0000
Subject: [PATCH] COFF: Take reference to argument vector using
 std::vector::data() instead of operator[](0).

This avoids undefined behaviour caused by an out-of-range access if the
vector is empty, which can happen if an object file's directive section
contains only whitespace.

llvm-svn: 240183
---
 lld/COFF/DriverUtils.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lld/COFF/DriverUtils.cpp b/lld/COFF/DriverUtils.cpp
index 7328606c64d5..129b1b43cbf5 100644
--- a/lld/COFF/DriverUtils.cpp
+++ b/lld/COFF/DriverUtils.cpp
@@ -557,7 +557,7 @@ ArgParser::parse(std::vector<const char *> Argv) {
   unsigned MissingIndex;
   unsigned MissingCount;
   std::unique_ptr<llvm::opt::InputArgList> Args(Table.ParseArgs(
-      &Argv[0], &Argv[0] + Argv.size(), MissingIndex, MissingCount));
+      Argv.data(), Argv.data() + Argv.size(), MissingIndex, MissingCount));
   if (MissingCount) {
     llvm::errs() << "missing arg value for \""
                  << Args->getArgString(MissingIndex)
@@ -587,7 +587,7 @@ std::vector<const char *> ArgParser::tokenize(StringRef S) {
 // character. '@<filename>' is replaced by the file's contents.
 ErrorOr<std::vector<const char *>>
 ArgParser::replaceResponseFiles(std::vector<const char *> Argv) {
-  SmallVector<const char *, 256> Tokens(&Argv[0], &Argv[0] + Argv.size());
+  SmallVector<const char *, 256> Tokens(Argv.data(), Argv.data() + Argv.size());
   BumpPtrStringSaver Saver(AllocAux);
   ExpandResponseFiles(Saver, TokenizeWindowsCommandLine, Tokens);
   return std::vector<const char *>(Tokens.begin(), Tokens.end());
-- 
2.34.1