Question

I’m using Dev-C++ v4.9.8.0 and I wrote the lines

const int i = 512;
i = 200;

and when I went to compile, I expected to see a compile-time error, but only got a warning. I told Dev-C++ that I want to compile this into a C program. My compiler under the hood is MinGW gcc v2.95, all of this running on a Windows 7 machine. I thought it was a language standard to generate a compile-time error when a program attempts to change a value declared with the const qualifier. Does the standard say this only warrants a warning?

Here’s my program:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
  const int i = 512;
  i = 250;

  system("PAUSE");  
  return 0;
}

And here’s the Compile Log:

7 C:\C_Programs\Practice\main.c
[Warning] assignment of read-only variable `i’

Answer 1

“Does the standard say this only warrants a warning?”

The standard make no distinction of warnings and errors. The standard only has diagnostic messages.

const int i = 512;
i = 200;

In this program, there is a constraint violation of the assignment operator. The implementation has to issue a diagnostic message. The compiler is then free to continue to translate this program. But a program with a constraint violation is not a C program.