[Lldb-commits] [lldb] [LLDB] Fix completion of space-only lines in the REPL on Linux (PR #83203)

[Walter Erquinigo via lldb-commits]

https://github.com/walter-erquinigo created https://github.com/llvm/llvm-project/pull/83203

https://github.com/modularml/mojo/issues/1796 discovered that if you try to complete a space-only line in the REPL on Linux, LLDB crashes. I suspect that editline doesn't behave the same way on linux and on darwin, because I can't replicate this on darwin.

Adding a boundary check in the completion code prevents the crash from happening.

>From 8dcc86a33bf10547f4a1c4175830b50a0508efe0 Mon Sep 17 00:00:00 2001
From: walter erquinigo <walter at modular.com>
Date: Tue, 27 Feb 2024 17:59:20 -0500
Subject: [PATCH] [LLDB] Fix completion of space-only lines in the REPL on
 Linux

https://github.com/modularml/mojo/issues/1796 discovered that if you try to complete a space-only line in the REPL on Linux, LLDB crashes. I suspect that editline doesn't behave the same way on linux and on darwin, because I can't replicate this on darwin.

Adding a boundary check in the completion code prevents the crash from happening.
---
 lldb/source/Host/common/Editline.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lldb/source/Host/common/Editline.cpp b/lldb/source/Host/common/Editline.cpp
index ce707e530d008b..e66271e8a6ee99 100644
--- a/lldb/source/Host/common/Editline.cpp
+++ b/lldb/source/Host/common/Editline.cpp
@@ -1029,8 +1029,11 @@ unsigned char Editline::TabCommand(int ch) {
     case CompletionMode::Normal: {
       std::string to_add = completion.GetCompletion();
       // Terminate the current argument with a quote if it started with a quote.
-      if (!request.GetParsedLine().empty() && request.GetParsedArg().IsQuoted())
+      Args &parsedLine = request.GetParsedLine();
+      if (!parsedLine.empty() && request.GetCursorIndex() < parsedLine.size() &&
+          request.GetParsedArg().IsQuoted()) {
         to_add.push_back(request.GetParsedArg().GetQuoteChar());
+      }
       to_add.push_back(' ');
       el_deletestr(m_editline, request.GetCursorArgumentPrefix().size());
       el_insertstr(m_editline, to_add.c_str());