CC = clang

all: redirect-dump

redirect-dump: redirect-dump.c

$(CC) -O0 -ggdb3 redirect-dump.c -o redirect-dump

clean:

$(RM) redirect-dump

.PHONY: all clean

This is a simple example on how to redirect an internal `dump` function and

return the dumped value as a string.

Run gdb and either use the redirect-dump.gdb file to load the extension, or do

so manually. Run and break in `break_here` and call the new `$dump_arr` function.

The result should be:

#include <stdlib.h>

#include <stdio.h>

void fdump_arr(FILE* stream, int* arr, size_t len)

{

for (int i = 0; i < len; ++i) {

fprintf(stream, "%d: %d\n", i, arr[i]);

}

}

void dump_arr(int* arr, size_t len)

{

fdump_arr(stdout, arr, len);

}

void break_here(int* arr, size_t len)

{

// Do nothing, set breakpoint here

}

int main(void)

{

int* arr = calloc(10, sizeof(int));

for (int i = 0; i < 10; ++i) {

arr[i] = i;

}

break_here(arr, 10);

free(arr);

return 0;

}

source redirect-dump.py

break break_here

import gdb

import tempfile

class DumpArr(gdb.Function):

"""Dump an array"""

def __init__(self):

super(DumpArr, self).__init__("dump_arr")

def invoke(self, arr, length):

with tempfile.NamedTemporaryFile() as tmp:

name = tmp.name

s = gdb.parse_and_eval('(FILE*)fopen("{}", "w")'.format(name))

gdb.parse_and_eval('fdump_arr({}, {}, {})'.format(s, arr, length))

gdb.parse_and_eval('(int)fclose({})'.format(s))

with open(name, 'r') as f:

return f.read()

DumpArr()