.arch armv6
    .fpu vfp
    .text

@ seg-fault at the end of the pgm!

    .global sub
sub:
    sub r0, r0, r1
    bx  lr

    .global add
add:
    push    {lr}
    add r0, r0, r1
    bl  sub
    pop {pc}

    .global main
main:
    mov r0, #5
    mov r1, #5
    bl  add
    mov r0, #1
end:

(gdb)
main () at stacks.s:24
24              mov     r0, #1
(gdb)
0x000083b8 in __libc_csu_init ()
(gdb)
Single stepping until exit from function __libc_csu_init,
which has no line number information.
Cannot access memory at address 0x0
add () at stacks.s:17
17              pop     {pc}
(gdb)
Cannot access memory at address 0x0

Program received signal SIGSEGV, Segmentation fault.
0x00000000 in ?? ()
(gdb)
Cannot find bounds of current function