How to use "printf" in raspberry pi assembly language

Question

Does printf has a limit to the number of values you can print?

Here is my code.

.data
.balign 4       
   string: .asciz "\n%d %d %d %d\n"        
.text
.global main
.extern printf

main:
    push    {ip, lr}        @ push return address + dummy register
                            @ for alignment
    ldr     r0, =string     @ get address of string into r0
    mov     r1, #11
    mov     r2, #22
    mov     r3, #33
    mov     r4, #444
    bl      printf          @ print string and pass params
                            @ into r1, r2, and r3
    pop     {ip, pc}        @ pop return address into pc

When I compile and execute this code it prints this:

11 22 33 1995276288

As you can see, the value in R4 does not print the right value.

I don't know why?

Because only the first 4 arguments are passed in registers. Sounds like you forgot to read the calling convention documentation. — Jester
– Jester, Commented Nov 5, 2016 at 19:15

Chris Dodd · Accepted Answer · 2023-10-08 20:36:20Z

11

Only the first 4 arguments are passed in registers (r0-r3) on the ARM -- any additional args are passed on the stack. Check out the procedure call ABI for details.

edited Oct 8, 2023 at 20:36

answered Nov 5, 2016 at 19:17

Chris Dodd

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2 Comments

Daniel Robert Webb Over a year ago

That explains the problem. Thanks

Peter Cordes Over a year ago

@DanielRobertWebb: then you should click the checkmark on this answer.

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