Descartes and C Programming

"Whatever I have up till now accepted as most true and assured I have gotten either from the sense or through the senses. But from time to time I have found that the senses deceive, and it is prudent never to trust completely those who have deceived us even once." - René Descartes

I have always been moved by the nature of thought that produced the ideas of Descartes and the Cartesian coordinate. Also, I am writing C codes for the last thirteen years. I would say that I find it to be the closest of the idea of the Cartesian coordinate.

I have not yet went through one standards of the C language fully. I have found C to be intuitive and I thought know how things can be achieved with it. I have been proven wrong earlier as well. Very recently, I wrote a code similar to this and it crashed with newer GCC.

	#include<stdio.h>
	#include<stdlib.h>
	#include<string.h>
	int main(int argc, char *argv[])
	{
	const char *const line= "25,82,42,71";
	const char *ptr= line;
	while(NULL!= ptr- 1) {
	/* I will check like above because I know NULL is 0x0 ;) */
	/* this essentially becomes "while(1)" */
	int type, val;
	if(2!= sscanf(ptr, "%d,%d", &type, &val)) { break; }
	ptr= strchr(ptr, ',')+ 1; ptr= strchr(ptr, ',')+ 1;
	/* I save so much by not checking for NULL here! */
	printf("%d: %d\n", type, val); fflush(stdout);
	}
	return 0;
	}

view raw nullptr.c hosted with ❤ by GitHub

It turns out, that if I perform pointer arithmetic, I tell the compiler that it is a valid pointer and it is guaranteed to be not equal to NULL and such checks can be optimised out (or "in")!

I tried with GCC-8.3.0 and 9.3.0 with "-O3" option and the latter crashes because the while always evaluates to true.

Please refrain from suggesting "better" ways to do something. This post is contains a snippet and not the whole code and the post is about standard behaviour and not how to write better C code ;)

Just like life, it is wise to be not too trusting with C.