# GDB

## gdb

* make sure debug flag is enabled when compiling the program. 
  * e.g., `gcc -g` 
  * e.g., `set(CMAKE_BUILD_TYPE RelWithDebInfo)` or `cmake -DCMAKE_BUILD_TYPE=Debug` 
* `gdb <program_name>`
* `gdb --args <program_name> arg1 arg2 arg3`
* `(gdb) break main` add a breakpoint at `main` function
* `(gdb) r` run the program
* `(gdb) list` list current function (in its original programming language)
* `(gdb) tbreak 48` add a temporary breakpoint at line 48 of current function
* `(gdb) c` continue running the program
* `(gdb) bt` print backtrace (of current stack)
* `(gdb) print <var>` print a variable
* `(gdb) info locals` print all local variables (of current stack)
* `(gdb) x /x 0x7fffffffd9b0` exam the memory at this address using hex format
* `(gdb) q` quit

More useful commands

* `(gdb) s` step into next function
* `(gdb) n` go to next instruction
* `(gdb) bt full` print full stack info including variables
* `(gdb) info args` print local `argc` and `argv` information&#x20;
* `(gdb) whatis v` check variable type
* `(gdb) disas` disassemble current function into assembly language
* `(gdb) list <filename:function_name>` list a function
* `(gdb) list <filename:line_number>` list a file around this line number
* `(gdb) tbreak 0x000055555576bf00` add a temporary breakpoint at the address (of an instruction)
* `(gdb) x /2xw 0xffff` print two-word length of the memory at this address using hex format
  * `b` byte, `h` half-word (2 bytes), `w` word (4 bytes), `g` giant word (8 bytes)
  * `x` hex, `a` pointer, `c` char, `d` integer, `u` uint, `s` string, `t` binary, `f` float, `o` octal

Fancy usage of extended gdb commands

* need to download and `source stl-views-1.0.3.gdb` ; can be added to `~/.gdbinit`&#x20;
* `(gdb) pvector <name>` print information about the STL vector class `std::vector<T>`&#x20;
* `(gdb) pmap <name>` print information about the STL map class `std::map<T,T>`&#x20;

references: [gdb cheatsheet](https://darkdust.net/files/GDB%20Cheat%20Sheet.pdf); [gdb commands](http://www.yolinux.com/TUTORIALS/GDB-Commands.html); [gdb STL support](https://sourceware.org/gdb/wiki/STLSupport); [download stl-views-1.0.3.gdb](https://sourceware.org/gdb/wiki/STLSupport?action=AttachFile\&do=view\&target=stl-views-1.0.3.gdb);&#x20;