From 966fac1941ea99e076a7654d229b27e1e6e4ad17 Mon Sep 17 00:00:00 2001
From: Sam McCall <sam.mccall@gmail.com>
Date: Mon, 9 Dec 2019 12:04:05 +0100
Subject: [PATCH] [clang][Tooling] Fix potential UB in
 ExpandResponseFilesCompilationDatabase

Summary:
`vector::assign` will cause UB at here.

fixes: https://github.com/clangd/clangd/issues/223

Reviewers: kadircet, sammccall, hokein

Reviewed By: sammccall

Subscribers: merge_guards_bot, ilya-biryukov, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D71172
---
 clang/lib/Tooling/ExpandResponseFilesCompilationDatabase.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Tooling/ExpandResponseFilesCompilationDatabase.cpp b/clang/lib/Tooling/ExpandResponseFilesCompilationDatabase.cpp
index 84936ba..9929831 100644
--- a/clang/lib/Tooling/ExpandResponseFilesCompilationDatabase.cpp
+++ b/clang/lib/Tooling/ExpandResponseFilesCompilationDatabase.cpp
@@ -61,7 +61,9 @@ private:
       llvm::StringSaver Saver(Alloc);
       llvm::cl::ExpandResponseFiles(Saver, Tokenizer, Argv, false, false, *FS,
                                     llvm::StringRef(Cmd.Directory));
-      Cmd.CommandLine.assign(Argv.begin(), Argv.end());
+      // Don't assign directly, Argv aliases CommandLine.
+      std::vector<std::string> ExpandedArgv(Argv.begin(), Argv.end());
+      Cmd.CommandLine = std::move(ExpandedArgv);
     }
     return Cmds;
   }
-- 
2.7.4