[Lldb-commits] [lldb] [lldb][ConstString] Prevent GetString from constructing a std::string with a nullptr (PR #95175)

[Michael Buch via lldb-commits]

https://github.com/Michael137 created https://github.com/llvm/llvm-project/pull/95175

This patch prevents passing a `nullptr` to the `std::string` constructor in `GetString`. This prevents UB arising from calling `GetString` on a default-constructed `ConstString`.

>From adacdee08b3d4f13beffff32ae3223a8272c15f7 Mon Sep 17 00:00:00 2001
From: Michael Buch <michaelbuch12 at gmail.com>
Date: Tue, 11 Jun 2024 22:23:56 +0100
Subject: [PATCH] [lldb][ConstString] Prevent GetString from constructing a
 std::string with a nullptr

This patch prevents passing a `nullptr` to the `std::string`
constructor in `GetString`. This prevents UB arising from
calling `GetString` on a default-constructed `ConstString`.
---
 lldb/include/lldb/Utility/ConstString.h    | 4 +++-
 lldb/unittests/Utility/ConstStringTest.cpp | 1 +
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/lldb/include/lldb/Utility/ConstString.h b/lldb/include/lldb/Utility/ConstString.h
index f7f7ec7605eba..692ecb63bd763 100644
--- a/lldb/include/lldb/Utility/ConstString.h
+++ b/lldb/include/lldb/Utility/ConstString.h
@@ -199,7 +199,9 @@ class ConstString {
   }
 
   /// Get the string value as a std::string
-  std::string GetString() const { return std::string(m_string, GetLength()); }
+  std::string GetString() const {
+    return std::string(AsCString(""), GetLength());
+  }
 
   /// Get the string value as a C string.
   ///
diff --git a/lldb/unittests/Utility/ConstStringTest.cpp b/lldb/unittests/Utility/ConstStringTest.cpp
index 716f2d8d6c804..7018248991b6e 100644
--- a/lldb/unittests/Utility/ConstStringTest.cpp
+++ b/lldb/unittests/Utility/ConstStringTest.cpp
@@ -88,6 +88,7 @@ TEST(ConstStringTest, NullAndEmptyStates) {
   EXPECT_TRUE(!null);
   EXPECT_TRUE(null.IsEmpty());
   EXPECT_TRUE(null.IsNull());
+  EXPECT_TRUE(null.GetString().empty());
 }
 
 TEST(ConstStringTest, CompareConstString) {