shoyu of lysu

0. Purpose

I’m a freshman to use gdb or c, because I mainly use java, but there is some situation for java programer to use gdb tools to solve problem. So I ‘mark’ this article~

1. Debug Target

gdb could debug many kinds of programming languages, like c, c++, objective-c, and so on. It doesn’t like debug tools in java, we often use it’s command-line interface instead of GUI.

Before we start to debug, we should take code compile with debug information.

for example, using gcc we should add -g flag

$ gcc example.c -g -o example

This is the reason why if we want to debug jvm, we must build it with debug info first.

2. Run as debug

using

$ gdb ./example

then we enter the gdb-commandline, and we can use tab key to complete or list all command

there are some basic command

	command	description
	dir [directories]	set source code folder
	r	run it
	b [where]	add a break, where is an express like ‘xx_method’ or linenum
	b [where] if [condition]	break when condition
	l	list code
	step	step into a method
	c	continue
	finish	finish current method
	p [var name]	watch a variable value
	x/? [address]	watch the memory address
	dump memory [file] [sadd] [eadd]	dump memory between to address into file
	info thread	list threads
	info break	list all break
	thread [tid]	switch thread
	bt	show stacktrace
	[enter]	redo last command

and so on…

2. Attach to running process

using

$ gdb ./example [pid]

to attach to pid process..

3. Run with coredump file

using

$ gdb ./example [coredump file path]

the previous blog tell some detail of debug coredump file.

Also see

• GDB调试程序