FLEX vs GDB

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.

GDB is a free debugger for inspecting a program as it runs or after it crashes. It can launch programs, stop execution under specified conditions, examine the stopped state, and change program state for experimentation. A target can run on the same machine, remotely, or in a simulator. GDB runs on popular UNIX variants, Microsoft Windows, and macOS, and supports languages including C, C++, Rust, Go, Ada, Fortran, Assembly, and others. Debugging options include conditional and exception breakpoints, core dump debugging, and record-and-replay with forward and reverse execution on supported platforms. For remote debugging, gdbserver connects a program to GDB. The console interpreter and GDB/MI are available, while Python extensions and the Debugger Adapter Protocol require Python support at build time. GDB is part of the GNU Project and is free software under the GNU General Public License, which allows copying, adaptation, and redistribution with source access. Official releases are available from GNU and Sourceware, with signature verification through the GNU keyring. Version 18.1 was released on September 25, 2026.