Multiple Return Values in Assembly Language

Assembly language doesn’t have built-in support for multiple return values or high-level concepts like functions in the same way as high-level languages. However, we can simulate similar behavior using registers and the stack. Here’s an approximation of the concept:

section .data
    fmt_int db "%d", 10, 0  ; Format string for printing integers

section .text
    global main
    extern printf

vals:
    ; Simulating returning two values by putting them in registers
    mov eax, 3  ; First return value
    mov ebx, 7  ; Second return value
    ret

main:
    ; Calling our "function"
    call vals
    
    ; The "returned values" are now in eax and ebx
    ; We'll print them using printf
    
    ; Print the first value (in eax)
    push eax
    push fmt_int
    call printf
    add esp, 8  ; Clean up the stack
    
    ; Print the second value (in ebx)
    push ebx
    push fmt_int
    call printf
    add esp, 8  ; Clean up the stack
    
    ; Simulating using only one of the returned values
    call vals
    ; We'll only use the second "returned" value (in ebx)
    push ebx
    push fmt_int
    call printf
    add esp, 8  ; Clean up the stack
    
    ; Exit the program
    mov eax, 1  ; sys_exit system call
    xor ebx, ebx  ; Exit code 0
    int 0x80  ; Make the system call

In this Assembly language version:

1. We define a vals routine that simulates returning two values by putting them in the eax and ebx registers.

2. In the main routine, we call vals and then use the values in eax and ebx as if they were returned values.

3. We use the printf function to print these values, which simulates the behavior of the original program.

4. To demonstrate using only one of the “returned” values, we call vals again but only use the value in ebx.

5. The concept of ignoring a return value (using _ in the original code) is simulated by simply not using the value in eax after the second call to vals.

This Assembly code provides a low-level approximation of the behavior of the original program. However, it’s important to note that Assembly doesn’t have built-in support for multiple return values, and this implementation is a simplification that doesn’t capture all the nuances of higher-level language features.

To run this program, you would need to assemble it into an object file, link it with the C library (for printf), and then execute the resulting binary. The exact commands would depend on your system and the assembler you’re using.