[DN-03]GDB 使用紀錄

開始試著用 GDB 來檢查追蹤程式流程和記憶體分配，跟著 GDB 來學習…
透過 GDB 來觀察 merge_soft 程式 https://github.com/Lukechin/mergesort_doubly_linked_list/blob/master/mergesort.c

首先使用 GDB 蹤程式前，需要在編譯階段增加 ”-g” 參數來產生 debugging info
我們先編譯 merge_soft.c 並產生含有 debugging info 的執行檔 ”merge_soft”

$ gcc -g -o merge_soft merge_soft.c

$ gcc -E -P

$ gdb merge_soft

b <line_number> - setting breakpoint at <line_number>
info b - print breakpoints information
disable b <break_number> - disable target breakpoint
continue - run after code…
Next - run next instruct (no entry sub function)
Step - run next instruct (entry sub funxtion)
List - list the source code and each execution’s corresponding line number
Backtrace - show trace of all function calls in stack
Info frame - List address, language, address of arguments/local variables and which registers were saved in frame.
- This will show where the return address is saved
- Return address is in Register EIP
- Calling stack pointer is in Register EBP
x &variable - show the address and value of a local variable (in hex format)
x address - print binary representation of 4 bytes of memory pointed to by address.