Costava

// Example compilation:
// gcc index_out_of_bounds.c -std=c99 -Wall -Wextra
//
// Compiles with ZERO warnings/errors on gcc 10.2.0
//
// Adding -O2 or above causes 2 warnings
//  for the printf line (this is by design of gcc, not a bug):
// array subscript -80 is below array bounds of ‘const int[5]’ [-Warray-bounds]
// array subscript 80 is above array bounds of ‘const int[5]’ [-Warray-bounds]
//

Costava

// Tested with gcc 10.2.0 and -std=c99
// Author: github.com/Costava

int main(void) {
    // gcc will NOT warn about this line from -Wall or -Wextra
    // -Wsign-conversion is needed:
    /// warning: unsigned conversion from ‘int’ to ‘unsigned int’ changes
    //           value from ‘-1’ to ‘4294967295’ [-Wsign-conversion]
    const unsigned int foo0 = -1;

Costava

// Example compilation:
// gcc fizzbuzz.c -std=c99 -Wall -Wextra

#include <stdio.h>

int main(void) {
	for (int i = 1; i <= 100; i += 1) {
		if (i % 3 == 0) {
			if (i % 5 == 0) {
				puts("FizzBuzz");

Costava

// Example compilation:
// gcc print_double.c -std=c99 -Wall -Wextra

#include <stdio.h>

int main(void) {
    double num;

    num = 0.25; printf("%f %a\n", num, num);// 0.250000 0x1p-2
    num = 0.50; printf("%f %a\n", num, num);// 0.500000 0x1p-1

Costava

// Example compilation:
// gcc typesizes.c -o typesizes -std=c99 -Wall

// Info on integer types: https://en.cppreference.com/w/c/types/integer

#include <stdint.h>
#include <stdio.h>

int main(void) {
	printf("sizeof(int):            %ld\n", sizeof(int));

Costava

// Sort of a benchmark --- if touching every pixel every frame,
//  a real program should not hope to get a higher frames per second
//  than this simple demo.
//
// Single process and thread.
// Every frame:
// - Set every pixel in array to fully opaque rand color.
// - SDL_UpdateTexture
// - SDL_RenderCopy
// - SDL_RenderPresent

Costava

// Sort of a benchmark --- if touching every pixel every frame,
//  a real program should not hope to get a higher frames per second
//  than this simple demo.
//
// Single process and thread.
// Using SDL_Renderer:
// - SDL_SetRenderDrawColor then SDL_RenderDrawPoint for each pixel each frame.

#include <stdbool.h>
#include <stdio.h>

Costava

Windows 10 locks shared NTFS partition(s)

Problem: Windows 10 locks shared NTFS partition(s). From Linux (multiple boot), files on the NTFS partition(s) cannot be deleted and programs depending on the partition's data cannot function properly.

Try 0: Shut down Windows

1. Boot into Windows
2. Shut down Windows (specifically not restart)

Costava

; Continuously print 'A' at boot
;
; Tested with NASM version 2.15.04
;         and QEMU emulator version 5.1.0
;
; To compile:
;     nasm -f bin real_mode_boot_to_A.asm -o real_mode_boot_to_A.bin
;
; To run:
;     qemu-system-x86_64 real_mode_boot_to_A.bin

Costava

// If a texture has format SDL_PIXELFORMAT_ABGR8888,
//  then the red component is the first byte in the pixels array of the texture
// Tested on a little-endian (x86) system
// Would the red component also come first in the array on a big-endian system?
//
// Tested with SDL2 version 2.0.12

#include <stdbool.h>
#include <stdio.h>
#include <stdint.h>