how to use gdb to explore the stack/heap?

Could anyone please开发者_开发技巧 give me a quick overview/point me to documentation of a way to inspect the stack (and heap?) of a C program? I thought this should be done with GDB, but if there are other more straighforward alternatives, then that should be fine as well.

Thanks.

you can dump raw memory with the 'x' command

so if you want to look at bits of the stack or heap try things like

x/10b &stackvar
x/200b &heapvar-20

The last one will show you 200 bytes starting from 20 bytes before heapvar. So if you just malloced that you can see the heap header too

View stack: gdb> backtrace

View current stack frame: gdb> info frame

View arguments of current stack frame: gdb> info args

View local variable of current stack frame: gdb> info locals

Navigate to parent stack frame: gdb> frame 1

Examining the Stack

My first approach to using GDB for debugging is to setup breakpoints. This is done like so:

prompt> gdb ./x_bstree.c
(gdb) #prompt
(gdb) b 123 #break at line 123
(gdb) r #start program

Now your program halts at line 123 of your program. Now you can examine variables in stack or heap using print. For stack variables just use print <varname>. For heap variables (pointers) use print <*varname>. Not sure there is anything special to do for examining stack/heap variables?

Of course to debug multi-threaded applications you would need to make it run in single-threaded mode & then dubug Otherwise it becomes difficult to predict what's happening.

For anything else there is extensive documentation of gdb & many sites also provide gdb cheat sheets.

Try using ddd. ddd manual

Ok. Maybe I elaborate a little. I use it like this.

compile my program with debug symbols:

gcc -g program.c -o program

run ddd:

ddd program

In gui you can do all sorts of things, view machine code, view memory, etc. . Look around. In manual there is also a section of examining stack. ddd provides good interface for you to examine C program.

core_analyzer has gdb plugin and stand alone tool.
Latest version is only gdb plugin.

gdb plugin command shows memory statistic.

(gdb)
heap  [/verbose or /v]  [/leak or /l]
heap  [/block or /b]  [/cluster or /c]  <addr_exp>
heap  [/usage or /u]  <var_exp>
heap  [/topblock or /tb]  [/topuser or /tu]  <num>

stand alone tool has horizontal search and vertical search and it might be near what you expect.

[0] Print General Core Information
[1] Find References to an Object (horizontal search)
[2] What Is This Address and Underlying Object Type (vertical search)
[3] Objects Shared Between Threads
[4] Memory Pattern Analysis
[5] Query Heap Memory Block
[6] Page Walk (check the integrity of surrounding memory blocks)
[7] Heap Walk (check the whole heap for corruption and memory usage)
[8] Biggest heap memory blocks
[9] Biggest Heap Memory Owners (variables)
[10] Heap Memory Leak Candidates
[11] Quit

In my case, I could not get exprected result from core_analyzer.