Custom Errors in Assembly Language

; Custom error structure
section .data
    argError:
        .arg     dd 0
        .message db "can't work with it", 0

; Function to print error message
section .text
global print_error
print_error:
    push ebp
    mov ebp, esp
    
    ; Print arg
    mov eax, 4
    mov ebx, 1
    mov ecx, [ebp+8]
    mov edx, 4
    int 0x80
    
    ; Print message
    mov eax, 4
    mov ebx, 1
    mov ecx, [ebp+12]
    mov edx, 17  ; Length of "can't work with it"
    int 0x80
    
    mov esp, ebp
    pop ebp
    ret

; Main function
global _start
_start:
    ; Call f(42)
    push 42
    call f
    add esp, 4
    
    ; Check if error occurred (eax will be -1 if error)
    cmp eax, -1
    jne no_error
    
    ; Print error
    push argError.message
    push argError.arg
    call print_error
    add esp, 8
    jmp end
    
no_error:
    ; Print result
    add eax, '0'  ; Convert to ASCII
    mov [result], eax
    mov eax, 4
    mov ebx, 1
    mov ecx, result
    mov edx, 1
    int 0x80
    
end:
    ; Exit program
    mov eax, 1
    xor ebx, ebx
    int 0x80

; Function f
f:
    push ebp
    mov ebp, esp
    
    ; Check if arg is 42
    cmp dword [ebp+8], 42
    jne not_42
    
    ; Return error
    mov eax, -1
    mov dword [argError.arg], 42
    jmp f_end
    
not_42:
    ; Return arg + 3
    mov eax, [ebp+8]
    add eax, 3
    
f_end:
    mov esp, ebp
    pop ebp
    ret

section .bss
    result resb 1

This Assembly Language code demonstrates a custom error implementation similar to the original Go example. Here’s a breakdown of the code:

We define a custom error structure argError with an arg field and a message field.
The print_error function is implemented to print the error message, which includes the arg value and the error message.
In the _start function (equivalent to main):
- We call f(42).
- If an error occurs (indicated by a return value of -1), we print the error message.
- If no error occurs, we print the result.
The f function:
- Checks if the argument is 42.
- If it is 42, it returns -1 (indicating an error) and sets the argError structure.
- Otherwise, it returns the argument plus 3.

This Assembly code mimics the behavior of the original Go code, including the custom error handling. However, it’s important to note that Assembly doesn’t have built-in error handling mechanisms like Go, so we have to implement error checking and handling manually.

To run this program, you would need to assemble it into an object file, link it, and then execute the resulting binary. The exact commands may vary depending on your system and assembler, but it might look something like this:

$ nasm -f elf custom_errors.asm
$ ld -m elf_i386 -o custom_errors custom_errors.o
$ ./custom_errors
42
can't work with it

This example demonstrates how to implement custom error handling in Assembly Language, albeit in a much more low-level and manual way compared to high-level languages like Go.

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Custom Errors in Assembly Language