While loop memory error in C

Question

My code goes something like this:
char* function(char* string){
char* check=string;
int found=0;
while(*check!='\0'){
if(*check>='0' && *check<='9'){
found=1;
break;
}
check++;
}

if(found==0)
return NULL;
}
.
.
.

And I get memory error (Process exited with code 139) in line where the while loop is. Why is this happening?

Answer 1

Additionallly, looking at the code, it seems you were checking whether the argument given contains any digit. In which case I would probably prefer to return an `int` to signal the caller whether there is any digit in the given argument.