How to print the next N executed lines automatically in GDB?

Question

I have been trying to find a way for some time to automate progress in GDB tracking program control flow.

Even an easy way to automate the n command so that you can see in which order the order is called.

I understand that you can release nx , where x is the number of GDB steps, but the problem is that it shows the command, but not the address of the subroutine! But if you press n manually in GDB (then press return to execute the previous command), it will display the address.

In GDB, I tried the following:

 (after setting a breakpoint at say 0x0123456) b *0x0123456 

GDB says <breakpoint 1 at 0x123456> . I am typing:

 commands 1 n 1000 c end 

but it does not loop as expected, and does not display the address: - (.

Any help would be appreciated! Of course, it should be just for automatic login, are the procedures called ??

Answer 1

How about using strace for system calls and ltrace for library calls to see traces instead of using gdb? strace for system calls and ltrace for library calls work with any application, even if you do not have the source code.

If you have access to the source code, you can also use your own code for tracking. Gcc has a mode that allows you to do this. Here is an example .

Then you only need to analyze the log files.

If you want to use simple GDB, you can use Breakpoint Command Lists

You can give any breakpoint (or watchpoint or breakpoint) a sequence of commands to execute when your program stops because of that breakpoint. For example, you can print the values ​​of certain expressions or include other breakpoints.

And in particular:

for example, here is how you could use breakpoint commands to print the value of x when entering foo whenever x is positive.

 break foo if x>0 commands silent printf "x is %d\n",x cont end 

Answer 2

It is simple, really. I will give you bare bones, and you can change them to your taste.

 (gdb) define nstep > set $foo = $arg0 > while ($foo--) > step > end > end (gdb) nstep 100 

I have done this many times. Hope this helps!

Answer 3

There is a shell script for automated calls to the trace function using gdb:

http://blog.superadditive.com/2007/12/01/call-graphs-using-the-gnu-project-debugger/

Since the link is now dead, I am posting a copy of the text here (author - Juan M. Bello Rivas - jmbr): http://web.archive.org/web/20090317091725/http://blog.superadditive.com/2007/12/ 01 / call-graphs-using-the-gnu-project-debugger /

Call graphs using the GNU project debugger

Chris Ball asked everyone who loves Unix for a tool that will make calls, which strace and ltrace are for system and library calls, respectively.

I wanted to write this myself for a long time, but what prevented me from doing this was that I came up with a trivial shell / awk script that achieved almost the same goal. Since this little program was useful for someone other than me, I thought Id would polish it a bit and post it here.

The purpose of these tools was to print a graph of calls from this program. It works by controlling GDB and automatically setting breakpoints with every function call. Of course, the executable should contain debugging symbols (that is, it must be compiled with the gccs -g option). Has some sample output (format: caller arguments):

 xmltree_parse xmltree_itor_next (self=0x80571e8) xmltree_itor_next xmlnode_stack_push (stack=0x80571f0, n=0x8056780) xmltree_parse h_requires (n=0x8056808, u=0xbff9d504) h_requires xmlnode_get_attr (self=0x8056808, name=0x80520ea "plugin") h_requires probe_get_name (self=0x8056af0) h_requires htab_lookup (self=0x8058100, key=0x8056868, len=3, create=0, value=0x0) 

You can use the included cg2dot.awk script to create files suitable for processing with graphviz .

Program (archive size 2110 bytes, md5 54b583e637d19be0502ccadfa6174756):

http://web.archive.org/web/20110902010824/http://superadditive.com/software/callgraph.tar.gz

It resets all functions from the program and generates a gdb batch file with breakpoints for each function. At each breakpoint, " backtrace 2 " and " continue " are executed (via commands ).

This script is rather slow in a large project (~ thousands of functions), so I added a filter to the list of functions (via egrep). It was very easy. I use this script almost every month.

PS: there is a copy of callgraph.tar.gz for the case when archive.org removes it from the archives. Use xxd -r to restore

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Answer 4

Fenris is the tool you are looking for, not gdb. Fenris Homepage

Written by legondary Michal Zalewski , exactly what you are looking for.

Answer 5

Here is my attempt at something similar using the python gdb API - c - GDB auto-detection - auto-print strings when run free?

Answer 6

I created a script for this specifically, it automates gdb to send 's', and then continuously output the output of gdb, and then output the result to a text file and to the terminal.

The script is in C and it is published on my blog.

http://www.codeground.net/coding/gdb-step-into-all-lines-to-get-full-application-flow/

I came to this question looking for this script, and could not find something like that, so I hope this helps someone else.

 wget http://www.codeground.net/downloads/gdbwalkthrough.c gcc gdbwalkthrough.c -o gdbwalkthrough ./gdbwalkthrough <application full path> [application arguments] 

This script can be easily modified to go through only a set of lines or to step only a predetermined number of times, just replace

 while(1) writeDebugger("s",NULL); 

with this

 int x=1000; while(x--) writeDebugger("s",NULL); 

Answer 7

AFAIK, it’s not easy to automate gdb. You can try insight to see if a small amount of tcl scritability will help you.

You can try to automate gdb / MI, and some expect a script.

In automatic debuggers, i'vd found that Sun dbx is better. It has "ksh" integrated into It. It is available on linux