Why is it allowed to modify a constant using a pointer in C?

Asked May 15 '18 at 00:34

Active May 15 '18 at 00:37

Viewed 34 times

I was wondering why it is allowed to modify a constant using a pointer?

int main( int argc, char ** argv ) {
  const int my_const = 9;
  int *ptr = &my_const;
  *ptr += 10;
  printf("%d", my_const);
  return 0;
}

This prints 19 without any error.
Is this a compiler specific behavior? (I am running gcc 4.7 on Windows)

Thanks...

asked May 15 '18 at 00:34

user6341457

1

It's not allowed. Your program breaks the rules of the language. Pay attention to the diagnostic messages emitted by the compiler – M.M May 15 '18 at 00:40
Curious, what did you expect the code to be required to do? Did you expect the code was required to stop and report a message? – chux - Reinstate Monica May 15 '18 at 02:31
Hi M.M, I actually ran the code. There was only a warning to use a constant integer pointer instead of the regular one. – user6341457 May 15 '18 at 02:36
Hi chux, I was expecting some kind of runtime error since I was modifying a constant. – user6341457 May 15 '18 at 02:37

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