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I typed help while I was in the GDB but didn't find anything about step-into, step-over and step-out. I put a breakpoint in an Assembly program in _start (break _start). Afterwards I typed next and it finished the debugging. I guess it was because it finished _start and didn't step-into as I wanted.

3
  • Read the full GDB docs. As I recall, they were quite helpful about this, when I was first learning it. Unfortunately, I haven't needed to debug any program at that level for several decades, so the actual commands seem to have gotten swapped out in my brain. So, I can't really write an answer. But, if you do figure it out from the manuals, then you can answer your own question for a bonus.
    – MAP
    Jul 24, 2016 at 17:32
  • @MAP I'll try again. I tried to use a better debugger (KDbg) but I don't succeed to use it in Ubuntu. Jul 24, 2016 at 17:38
  • gdb is a good debugger. You may want to use Emacs as its frontend. Jan 2, 2020 at 6:50

3 Answers 3

83

help running provides some hints:

There are step and next instuctions (and also nexti and stepi).

(gdb) help next
Step program, proceeding through subroutine calls.
Usage: next [N]
Unlike "step", if the current source line calls a subroutine,
this command does not enter the subroutine, but instead steps over
the call, in effect treating it as a single source line.

So we can see that step steps into subroutines, but next will step over subroutines.

The step and stepi (and the next and nexti) are distinguishing by "line" or "instruction" increments.

step -- Step program until it reaches a different source line
stepi -- Step one instruction exactly

Related is finish:

(gdb) help finish
Execute until selected stack frame returns.
Usage: finish
Upon return, the value returned is printed and put in the value history.

A lot more useful information is at https://sourceware.org/gdb/onlinedocs/gdb/Continuing-and-Stepping.html

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  • What does it mean by until it reaches a different source line? Jul 24, 2016 at 18:04
  • 2
    for(i=0;i<10;i++) { printf("%d\n",i); } is one source line but multiple instructions. Jul 24, 2016 at 18:06
  • 7
    Is there a way to step-out? I couldn't find it in help running.
    – nukeguy
    Aug 23, 2017 at 16:34
  • 4
    What do you mean by "step-out"? The finish command will complete the current stack frame, which will normally complete the current subroutine and return to the caller. Aug 24, 2017 at 2:03
  • 5
    finish or fin in GDB, is the step-out in IDEA or Eclipse.
    – Eric
    Feb 23, 2020 at 8:18
6

Use command 'finish'; this sometimes does the same thing as 'step-out'. It'll finish what the stack is doing (a function, usually), and go to the next line after that. Look up the command for more info.

3

I came here because I had the same question. I eventually figured that for my purpose any time I could use something like "step-out" of a loop I can just set another breakpoint after the loop and then let the program continue to finish the loop and run into the breakpoint afterward. Sorry if that is obvious to most people but it is probably helpful for someone looking for an answer to this question.

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  • 1
    "Step out" in most other debuggers is "finish" in gdb. Not really to do with exiting a loop.
    – RichieHH
    Mar 2, 2021 at 19:00

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