debugger gdb evaluate expression - gdb

Question

is there eval function? I've read "help" and I didnt find
I want to make eval("gdb command")
because I want to create my own function for grepping using this method
How to grep on gdb print.
I want to make eval($arg1)

Answer 1

There is an eval command, but it doesn't really do what you want. It provides a limited form of substitution of values into commands.
For a command along the lines of grep, I would suggest writing it in Python. This would be relatively easy to do. The idea would be to use gdb.execute to capture the output of a command into a string, and then use Python to search the string however you like. If done from Python you have complete control of how to parse the command-line, something that's not true if you use the gdb define command.

Answer 2

Oddly enough, I wrote a grep python gdb function earlier today for another question. These couple of files make a new command that checks if the call stack contains _malloc. This should be a pretty good start for other string searching and evaluation functions.
Here is a script for gdb
# gdb script: pygdb-logg.gdb
# easier interface for pygdb-logg.py stuff
# from within gdb: (gdb) source -v pygdb-logg.gdb
# from cdmline: gdb -x pygdb-logg.gdb -se test.exe
# first, "include" the python file:
source -v pygdb-logg.py
# define shorthand for inMalloc():
define inMalloc
python inMalloc()
end
Here is the python file:
#!/usr/bin/python
# gdb will 'recognize' this as python
# upon 'source pygdb-logg.py'
# however, from gdb functions still have
# to be called like:
# (gdb) python print logExecCapture("bt")
import sys
import gdb
import os
def logExecCapture(instr):
# /dev/shm - save file in RAM
ltxname="/dev/shm/c.log"
gdb.execute("set logging file "+ltxname) # lpfname
gdb.execute("set logging redirect on")
gdb.execute("set logging overwrite on")
gdb.execute("set logging on")
gdb.execute("bt")
gdb.execute("set logging off")
replyContents = open(ltxname, 'r').read() # read entire file
return replyContents
# in malloc?
def inMalloc():
isInMalloc = -1;
# as long as we don't find "Breakpoint" in report:
while isInMalloc == -1:
REP=logExecCapture("n")
#Look for calls that have '_malloc' in them
isInMalloc = REP.find("_malloc")
if(isInMalloc != -1):
# print ("Malloc:: ", isInMalloc, "\n", REP)
gdb.execute("set $inMalloc=1")
return True
else:
# print ("No Malloc:: ", isInMalloc, "\n", REP)
gdb.execute("set $inMalloc=0")
return False