Parker Olson Parker Olson - 7 days ago 6
C Question

glCreateShader is crashing

I should have the newest version of Glew and Glut so that shouldn't be the problem. Everything should be linked, and I'm using MS visual studio 2010.
My program compiles but when I get to glCreateShader(GL_FRAGMENT_SHADER) it show an error: "0xC0000005: Access violation."

my program:

#include <GL\glew.h>
#include <GL\glut.h>
#include <stdio.h>
#include <stdlib.h>

GLuint program;

static char* readShaderSource(const char * shaderFile)
{
FILE* fp = fopen(shaderFile, "r");
char* buf;
long size;

if (fp == NULL) return NULL;
fseek(fp, 0L, SEEK_END);//go to end
size = ftell(fp); //get size
fseek(fp, 0L, SEEK_SET);//go to begining

buf = (char*) malloc((size +1) * sizeof(char));
fread(buf, 1, size, fp);
buf[size] = NULL;
fclose(fp);
return buf;
}

static void initShader(const GLchar * fsFile)
{
GLint status;
GLchar * fSource;
GLuint fShader;
GLuint fShader2;

//read file
fSource = readShaderSource(fsFile);
if (fSource == NULL)
{
printf("Fail to load file");
exit(EXIT_FAILURE);
}

//Create program and shader object
fShader2 = glCreateShader(GL_VERTEX_SHADER);
fShader = glCreateShader(GL_FRAGMENT_SHADER);
program = glCreateProgram();

//Attach shaders to program
glAttachShader(program, fShader);

//read shaders
glShaderSource(fShader, 1, (const GLchar**) &fSource, NULL);

//compile fragment shader
glCompileShader(fShader);

//error check
glGetShaderiv(fShader, GL_COMPILE_STATUS, &status);
if (status == GL_FALSE)
{
printf("Failed to compile the fragment shader.");
exit(EXIT_FAILURE);
}

//link and error check
glLinkProgram(program);
glGetProgramiv(program, GL_LINK_STATUS, &status);
if (status == GL_FALSE)
{
printf("program error");
exit(EXIT_FAILURE);
}

//use program object
glUseProgram(program);

//set up uniform parameter
//skipped for now
}

int main(int argc, char ** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(500,500);
glutCreateWindow("Matrix Fractal");
glClearColor(1.0, 1.0, 1.0, 1.0);
gluOrtho2D(0.0,0.0,(GLfloat) 500, (GLfloat) 500);

glutDisplayFunc(draw);
glutReshapeFunc(reshape);

initShader("fsFractal.glsl");

glutMainLoop();
}

Answer

You have to initialize GLEW before you can use it:

GLenum err = glewInit();

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