(windows) DevC++ GCC compiler hangs up or prints infinite characters - c

Question

I am trying to write some C code, and while running the following, my compiler terminates abruptly, after printing 'A'. Why?
//report expected thing
void Expected(char *s){
int i=0;
int n = sizeof(s)/sizeof(s[0]);
while (i< n)
printf ("%c", s[i]);
printf(" expected.\n");
}
int main(int argc, char *argv){
printf("%c",65); //after this compiler hangs and asks for exit abnormally
char *Arr ={'a'};
Expected(Arr);
return 0;
}
Also, if I put
char *Arr ={"a"}; //note the double quotes
then it starts printing out infinite number of 'a's. Why should this happen?

Answer 1

int n = sizeof(s)/sizeof(s[0]);
is not how to get the length of the array of which the pointer passed as the argument points at the first element.
Pass the size of the array if you want to let your function know that.
char *Arr ={'a'};
Is not good because 'a' is a integer and you converted it to a pointer, then the result has too little chance to be a valid pointer.
char *Arr ={"a"};
is OK because it is a valid pointer, but it will be infinite loop because i is not updated in the while loop.
The type of main() function is implementation-defined. You should use standard type unless you have some reason to use special main().
Your code should be like this:
#include <stdio.h>
//report expected thing
void Expected(const char *s, size_t n){ /* add const because the contents of array won't be modified */
size_t i=0; /* use size_t to match type of n */
while (i < n)
printf ("%c", s[i++]); /* update i */
printf(" expected.\n");
}
int main(void){ /* use standard main(). int main(int argc, char **argv) is the another standard type */
printf("%c",65); //after this compiler hangs and asks for exit abnormally
char Arr[] ={'a'}; /* declare an array instead of a pointer */
Expected(Arr, sizeof(Arr)/sizeof(Arr[0]));
return 0;
}
Finally, if it is really not your produced executable but your compiler that is crashing, throw the broken compiler away and get a new one.