Why should I always enable compiler warnings?

Question

I often hear that when compiling C and C++ programs I should \"always enable compiler warnings\". Why is this necessary? How do I do that?

Sometimes I also hear tha

Answer 1

This is a specific answer to C, and why this is far more important to C than to anything else.

#include 
int main()
{
   FILE *fp = "some string";
}

This code compiles with a warning. What are and should be errors in just about every other language on the planet (barring assembly language) are warnings in C. Warnings in C are almost always errors in disguise. Warnings should be fixed, not suppressed.

With gcc, we do this as gcc -Wall -Werror.

This was also the reason for the high rantyness about some MS non-secure API warnings. Most people programming C have learned the hard way to treat warnings as errors and this stuff appeared that just wasn't the same kind of thing and wanted non-portable fixes.