FLEX vs LLDB

FLEX is a free, open-source debugging and exploration library for iOS applications. It runs inside the app and places a toolbar in a window above it, allowing developers to inspect and change application state without an LLDB or Xcode connection or a remote debugging server. The tool can inspect view hierarchies, find live heap objects, show and modify properties and ivars, and call methods. Its network history covers NSURLConnection and NSURLSession requests with timing, headers, and responses. Developers can browse app bundles and sandboxes, inspect SQLite and Realm databases, and view or edit NSUserDefaults values, including strings, numbers, arrays, and dictionaries. FLEX works in the iOS Simulator and on physical devices, supports Objective-C and Swift, and requires an iOS 9-or-later target. Installation options include CocoaPods, Carthage, Buck, manual Xcode integration, and Swift Package Manager.

LLDB is a free debugger built from reusable components that use LLVM libraries, including Clang's expression parser and the LLVM disassembler. It is the default debugger in Xcode on macOS and supports debugging C, C++, and Objective-C on desktop and iOS devices and simulators. Its tools include breakpoints, watchpoints, process launching, and attaching to programs; remote debugging is also documented for Linux, Windows, Android, and iOS. Expression evaluation uses Clang infrastructure for current C-family language features, multiline expressions, and just-in-time evaluation where supported. Developers can use its shared-library C++ API and Python bindings for scripting, symbolication, disassembly, and inspecting object and symbol files. The lldb-dap adapter connects LLDB functionality to compatible editors and IDEs, including Visual Studio Code, Emacs, vim, and neovim. LLDB is available under the Apache 2.0 License with LLVM exceptions. Windows support remains under active development, with ARM and AArch64 described as more experimental. The lldb-dap interface documents no support for step-back, setting a variable, goto-target, or terminate requests.