GDB print all values in char array

Question

I am storing various filenames in my array which are partitioned by null bytes. When debugging, I am only able to see the first filename. So, for instance if my array is like this: hello.txt00000hello2.txt, I am only able to see hello.txt. How can I print the entire array? I have trouble finding such command elsewhere.

Answer 1

With gdb, you can achieve to print the elements of your array using the following command:

(gdb) print *array@size

If my variable array is a type char*[] such as below

const char *array[] = {"first","second","third"};

Then I could display the 2 first char* entries of my array by using:

(gdb) print *array@2
$2 = { 0x..... "first", 0x..... "second"}

Using it in order to display the arguments of a program is very handy:

(gdb) print *argv@argc

It's also possible to do the same with x commands using x/Ns *argv, where N is the integer value of argc (i.e. for argc = 2, x/2s *argv)

The documentation for the whole magic of the print command is here.

Answer 2

You can use x/999bc, where 999 is the size of your array, for instance:

paul@thoth:~/src/sandbox$ gdb ./str
GNU gdb (GDB) 7.4.1-debian
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/paul/src/sandbox/str...done.
(gdb) list
1   int main(void) {
2       char * p = "hello\0world\0hahaha";
3       return 0;
4   }
5   
(gdb) b 3
Breakpoint 1 at 0x4004b8: file str.c, line 3.
(gdb) run
Starting program: /home/paul/src/sandbox/str 

Breakpoint 1, main () at str.c:3
3       return 0;
(gdb) print p
$1 = 0x40056c "hello"
(gdb) x/19bc p
0x40056c:   104 'h' 101 'e' 108 'l' 108 'l' 111 'o' 0 '\000'    119 'w' 111 'o'
0x400574:   114 'r' 108 'l' 100 'd' 0 '\000'    104 'h' 97 'a'  104 'h' 97 'a'
0x40057c:   104 'h' 97 'a'  0 '\000'
(gdb)