Writing Secure C and Secure C Idioms

Question

\"The average man does not want to be free. He simply wants to be safe.\" - H. L. Menken

I am attempting to write very secure C. Below I

Answer 1

Don't use gets() for input, use fgets(). To use fgets(), if your buffer is automatically allocated (i.e., "on the stack"), then use this idiom:

char buf[N];
...
if (fgets(buf, sizeof buf, fp) != NULL)

This will keep working if you decide to change the size of buf. I prefer this form to:

#define N whatever
char buf[N];
if (fgets(buf, N, fp) != NULL)

because the first form uses buf to determine the second argument, and is clearer.

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Check the return value of fclose().

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