GDB debugger skill for C/C++ programs. Use when starting a GDB session, setting breakpoints, stepping through code, inspecting variables, debugging crashes, using reverse debugging (record/replay), remote debugging with gdbserver, or loading core dumps. Activates on queries about GDB commands, segfa

GDB Purpose Walk agents through GDB sessions from first launch to advanced workflows: crash diagnosis, reverse debugging, remote debugging, and multi thread inspection. Triggers "My program segfaults / crashes — how do I debug it?" "How do I set a breakpoint on condition X?" "How do I inspect memory / variables in GDB?" "How do I debug a remote embedded target?" "GDB shows ?? frames / no source" "How do I replay a bug deterministically?" (record/replay) Workflow 1. Prerequisite: compile with debug info Always compile with g (GCC/Clang). Use Og or O0 for most debuggable code. For release builds: use g O2 and keep the binary with symbols (strip separately with objcopy ). 2. Start GDB 3. Essential commands Command Shortcut Effect run [args] r Start the program continue c Resume after break next n Step over (source line) step s Step into nexti ni Step over (instruction) stepi si Step into (instruction) finish Run to end of current function until N Run to line N return [val] Force return from function quit q Exit GDB 4. Breakpoints and watchpoints 5. Inspect state 6. Multi thread debugging 7. Reverse debugging (record/replay) Record requires target record full or target record btrace (Intel PT): 8. Remote debugging with gdbserver On target: On host: For cross compilation: use aarch64 linux gnu gdb on the host. 9. Common problems Symptom Cause Fix No symbol table Binary not compiled with g Recompile with g ?? frames in backtrace Missing debug info or stack corruption Install debuginfo package; check for stack smash Cannot access memory at address Null dereference / freed memory Check pointer before deref; use ASan SIGABRT in backtrace abort() or assertion failure Go up frames to find the assertion GDB hangs on run Binary waiting for input Redirect stdin: run < /dev/null Breakpoint in wrong place Optimiser moved code Compile with Og ; or use nexti 10. GDB init file (~/.gdbinit) For a command cheatsheet, see [references/cheatsheet.md](references/cheatsheet.md). For pretty printers and Python scripting, see [references/scripting.md](references/scripting.md). Related skills Use skills/debuggers/core dumps for loading core files Use skills/debuggers/lldb for LLDB based workflows Use skills/runtimes/sanitizers to catch bugs before needing the debugger Use skills/compilers/gcc for g flag details