如何在ARM汇编中打印数字? [英] How to print a number in ARM assembly?

问题描述

我正在尝试打印我已存储的号码.我不确定我是否要关闭或离开.任何帮助将不胜感激.这是我的代码:

I am trying to print a number that I have stored. I'm not sure if I am close or way off. Any help would be appreciated though. Here is my code:

.data
.balign 4
a: .word 4

.text
.global main
main:
        ldr r0, addr_of_a
        mov r1, #8
        str r1, [r0]
write:
        mov r0, #1
        ldr r1, addr_of_a
        mov r2, #4
        mov r7, #4
        swi #0
        bx lr

addr_of_a: .word a

它可以编译并运行，但是我看不到任何内容.据我了解，我需要在r1中开始打印的地址，r2中有多少字节，r0中的文件描述符以及r7(如果将其设置为#4)指定写调用的地址.我只是想存储#8，然后打印存储的号码.

It compiles and runs, but I don't see anything printed. From what I understand, I need the address of where to start printing in r1, how many bytes in r2, the file descriptor in r0, and r7 specifies the write call if it is set to #4. I am simply trying to store #8, then print the stored number.

推荐答案

系统调用写入将第二个参数(r1)作为指向您要打印的字符串的指针.您正在向它传递一个指向整数的指针，这就是为什么它不打印任何内容的原因，因为要传递给它的内存区域中没有ASCII字符.

The syscall write takes on the second argument (r1) as a pointer to the string you want to print. You are passing it a pointer to an integer, which is why it's not printing anything, because there are no ASCII characters on the memory region you are passing to it.

在下面，您将使用syscall写入找到一个"Hello World"程序.

Below you'll find a "Hello World" program using the syscall write.

.text
.global main
main:
        push {r7, lr}

        mov r0, #1
        ldr r1, =string
        mov r2, #12
        mov r7, #4
        svc #0

        pop {r7, pc}

.data
string: .asciz "Hello World\n"

如果要打印数字，可以使用C库中的printf函数.像这样:

If you want to print a number you can use the printf function from the C library. Like this:

.text
.global main
.extern printf
main:
        push {ip, lr}

        ldr r0, =string
        mov r1, #1024
        bl printf

        pop {ip, pc}

.data
string: .asciz "The number is: %d\n"

最后，如果要使用syscall写入来打印数字，还可以实现itoa函数(将整数转换为字符串的函数).

Finally, if you want to print the number with the syscall write you can also implement a itoa function (one that converts an integer to a string).

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