CPU Asm Exercise: Processing Text in Assembly Language and C Language errors and warning once debugged-Frdm-KL25Z board

#include "MKL25Z4.h" // Device header

__asm void my_strcpy(const char *src, char *dst)
{
loop
LDRB r2, [r0] //; Load byte into r2 from memory pointed to by r0 (src pointer)
ADDS r0, #1 //; Increment src pointer
STRB r2, [r1] //; Store byte in r2 into memory pointed to by (dst pointer)
ADDS r1, #1 //; Increment dst pointer
CMP r2, #0 //; Was the byte 0?
BNE loop //; If not, repeat the loop
BX lr //; Else return from subroutine
}
__asm void my_capitalize(char *str)
{
cap_loop
LDRB r1,[r0] //; Load byte into r1 from memory pointed to by r0 (str pointer)
CMP r1, #'a'-1 //; compare it with the character before 'a'
BLS cap_skip //; If byte is lower or same, then skip this byte

CMP r1, #'z' //; Compare it with the 'z' character
BHI cap_skip //; If it is higher, then skip this byte

SUBS r1,#32 //; Else subtract out difference to capitalize it
STRB r1,[r0] //; Store the capitalized byte back in memory
cap_skip
ADDS r0, r0, #1 //; Increment str pointer
CMP r1, #0 //; Was the byte 0?
BNE cap_loop //; If not, repeat the loop
BX lr //; Else return from subroutine
}

int main(void)
{
const char a[] = "Hello world!";
char b[20];

my_strcpy (a, b);
my_capitalize(b);
while (1);
}

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