GDB === ###### tags: `Debug` `Linux Tools` ## Basic Commands ### Quick Start - [Introduction to GDB a Tutorial - Harvard CS50](https://www.youtube.com/watch?v=sCtY--xRUyI) ### Compile & Debug ``` gcc -g -Werror -o hello hello.c gdb -tui hello ``` :::info -Werror make all warnings into errors. ::: ### TUI commands * Display the named window: ```layout src```, ```layout asm```, ```layout regs``` * Set the focus to the named window: ```focus src```, ```focus asm```, ```focus regs``` * Change the height of the window name by count lines: ```winheight name +count```, ```winheight name -count``` ### Save command history ``` set history filename ./gdb_cmd_history set history save on SOME COMMAND SOME COMMAND SOME COMMAND quit ``` 重開GDB ``` source ./gdb_cmd_history ``` ## Glossary * Endianness 位元組順序(Endianness)是指資料在記憶體中的放置順序，不同的 CPU架構可能會採用不同的放置規則，若遇到需要在不同機器或是網路之間交換低階的二進位資料時，就必須注意這個問題。 * Memory Pointer Register * Program Pointer A register that points to where the data immediately need to be accessed by processor. * Frame Pointer(=Local Base Pointer) vs. Stack Pointer SP指向stack的最頂端(最低位址)。 FP指向stack的固定位址，以FP計算local variable和parameter較方便。 ![](https://i.imgur.com/dxyE9KJ.png) :::info Stack: reserved RAM memory for temporary data storage. ::: * Symbol Table There are two sets of symbols that gdb uses: * Debugging symbols The gcc **-g** option set allows to see source code and variables while debugging. * Linking symbols This set lives in the ELF (Executable Linkable Format) symbol table that contain addresses of the things in your executable, library, or object file. ## Tutorials - [RMS's gdb Debugger Tutorial](http://www.unknownroad.com/rtfm/gdbtut/gdbtoc.html) - [基本gdb](http://www.study-area.org/cyril/opentools/opentools/x1253.html) - [進階gdb](http://www.study-area.org/cyril/opentools/opentools/x1265.html)