How to pass arguments to a python gdb script launc

Question

I'd like to pass some command line arguments to a python script run via gdb command, but importing the gdb module in python removes the argv attribute from sys. How do I access arg1 and arg2 within my python script shown in my example?

Command line execution:

$ gdb -x a.py --args python -arg1 -arg2

a.py:

#!/usr/bin/env python
import gdb
import sys
print('The args are: {0}'.format(sys.argv))
gdb.execute('quit')

Error raised:

AttributeError: 'module' object has no attribute 'argv'

Versions:

• GNU gdb (GDB) 7.2
• Python 2.6.6

Edit:

The end target I'll be debugging is a C executable that is already running, so I'll be attaching to it later in the script, so gdb -x a.py --args python -arg1 -arg2 is not correct either since the python part prints a gdb error: Reading symbols from /usr/bin/python...(no debugging symbols found)...done....

Answer 1

It's not totally clear to me what you are trying to do.

An invocation of the form:

gdb --args something arg arg

Tells gdb to use something as the program to be debugged, with arg arg as the initial command-line arguments for the run command. You can inspect these inside gdb with show args.

So, your command is saying "I want to debug the python executable, passing it some arguments".

However, later you say you plan to attach to some already-running executable.

So, I think you're probably trying to script gdb in Python -- not debug the python executable.

The good news is, this is possible, just not the way you've written it. Instead you have a couple choices:

• Make a .py file holding your script and tell gdb to source it, e.g., with gdb -x myscript.py (which you've already done...)

• Use -ex to invoke some Python explicitly, like -ex 'python print 23'.

Answer 2

-ex py

This is a possibility:

argv.py:

print(arg0)
print(arg1)

Invocation:

gdb --batch -ex 'py arg0 = 12' -ex 'py arg1 = 3.4' -x argv.py

Then you could wrap that in the following script:

#!/usr/bin/env bash

doc="
Pass parameters to python script.

Usage:

  $0 scrpit.py 1 2

Where scrpit.py uses the arguments like:

  print(arg0)
  print(arg1)
"

py="$1"
shift
cli=''
i=0
for arg in $*; do
  cli="$cli -ex 'py arg$i = $arg'"
  i=$(($i+1))
done
eval gdb --batch $cli -x "$py"