stdout not working properly with linked assembly function in simple c program-CodePudding

I am trying to learn arm assembly currently, and I've been toying with blending c and asm together. What I made was a simple program that will enter an infinite loop (written in assembly) where a string is output to the console. The problem that I've run into is that the output when I run the assembly code by itself works as expected, but when I try to access the function from inside a C program, then the output is not the same as it was originally.

sample.c

#include <stdio.h>

void loop();

int main (void){

        printf("Before loop:\n");
        loop();
        printf("After loop:\n");

}

assembly.s

.global loop

loop:
        MOV R0, #1
        LDR R1, =message
        LDR R2, =len
        MOV R7, #4
        SWI 0
        b loop

.data
message:
        .asciz "Hello from inside loop\n"

len = .-message

I compiled it as follows

as assembly.s -o assembly.o
ld assembly.o -o assembly
gcc sample.c assembly -o sample
./sample
Before loop:

^C

However when I run the asm by itself, it runs without issue. Anyone have a second to explain this to me?

    ./assembly
    Before loop:
    Hello from inside loop
    Hello from inside loop
    Hello from inside loop
    Hello from inside loop
    ^C

EDIT: for clarification, there was a long string of unicode characters after the C version of the program, that were filtered out of this post. It was not the appropriate output but there was an infinite string of some character.

CodePudding user response：

As Jester stated in their comment, the answer is that I was not compiling correctly:

You need to link the object file not the executable. So do
gcc sample.c assembly.o -o sample
Note gcc can invoke the assembler for you so can do it in one step:
gcc sample.c assembly.s -o sample