I'm pretty new to programming, so I've been reading like, almost every HOWTO on C++.

I'm tring to run a program that uses the memset() function. It compiles fine, but during runtime, i get the ever-notorious "Segementation fault(core dumped)" error - which i've googled and read a million reasons why that error occurs. Usually due to accessing memory that hasn't yet been initialized.

the program sets up MCGA mode, sets up a function to set the screen a certain color, and sets up a funtion to put a pixel on the screen.

i put a small Main() function at the bottom to test out the functions.


#include <iostream>
#include <stdlib.h>
#include <cstring>


char vga[0xffff];

void setMCGA() {
asm("mov $0x13, %ax");
asm("int $0x10");
}

void screenSet(int color) { //int color is a number between 0 and 255

memset(vga, color, 0xffff);//0xffff = 64000
}

void pixelPut (int x, int y, unsigned char color) {

memset(vga-x-(y*320), color, 1);
}

int main() {
setMCGA();
screenSet(200);
pixelPut(300, 200, 0);
return 0;
}


I somehow think that my runtime error is due to my lack of knowledge on the memset() function. I've looked up usage for it, and I believe I'm doing this right, but apparently not.

Does anyone know??

thanks
giuseppe

A quick look tells me this is the suspect code

I agree with dmail.

To elaborate:
There's no such thing as "x=320, y=200" in a 320x200 video buffer. The coordinate range is "x=0..319, y=0..199".

'Hope that helps .. pSM