Bp on a matching string. Run as `gcc test.c; gdb -q -x bp.py ./a.out`

bp.py

import gdb

class MyBreakpoint (gdb.Breakpoint):
    def stop (self):
        rdi = int(gdb.parse_and_eval("$rdi").cast(gdb.lookup_type('uint64_t')))
        print("x(%x)" % (rdi)), 
        result = gdb.selected_inferior().read_memory(rdi, 10)
        if b'\x00' in result:
            result = bytearray(result).split(b'\x00')[0]
        if result == b'pol': # breaks if True is returned else just continues
            return True
        return False

MyBreakpoint("x")

test.c

/*
 * untitled.c
 *
 * Copyright 2018 Sudhakar Verma <sudhakar@payatu.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02110-1301, USA.
 *
 *
 */


#include <stdio.h>
void x(char *in){
    puts(in);
}

int main(int argc, char **argv){
    x("lol");
    x("pol");
    x("dol");
    return 0;
}