code error : Thread 1: EXC_BAD_ACCESS (code=1, address=0x0) - c++

Question

I'm trying to write a code in C ++ using OpenGL (I use GLFW and GLEW libraries). Here is the code:
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#define numVAOs 1
GLuint renderingProgram;
GLuint vao[numVAOs];
GLuint createShaderProgram(){
const char*vshaderSource =
"#version 430 \n"
"void main(void) \n"
"{gl_Position = vec4(0.0,0.0,0.0,1.0)};";
const char*fshaderSource =
"#version 430 \n"
"out vec4 color; \n"
"void main(void) \n"
"{gl_Position = vec4(0.0,0.0,1.0,1.0)};";
GLuint vShader = glCreateShader(GL_VERTEX_SHADER);
GLuint fShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(vShader,1,&vshaderSource,NULL);
glShaderSource(fShader,1,&fshaderSource,NULL);
glCompileShader(vShader);
glCompileShader(fShader);
GLuint vfProgram = glCreateProgram();
glAttachShader(vfProgram,vShader);
glAttachShader(vfProgram,fShader);
glLinkProgram(vfProgram);
return vfProgram;
}
int main()
{
glfwInit();
// Define version and compatibility settings
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
glfwWindowHint(GLFW_OPENGL_PROFILE,GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
glGenVertexArrays(numVAOs,vao);
glBindVertexArray(vao[0]);
glUseProgram(renderingProgram);
glDrawArrays(GL_POINT,0,1);
// Create OpenGL window and context
GLFWwindow* window = glfwCreateWindow(1430, 800, "Davide", NULL, NULL);
glfwMakeContextCurrent(window);
// Check for window creation failure
if (!window)
{
// Terminate GLFW
glfwTerminate();
return 0;
}
glewExperimental = GL_TRUE; glewInit();
// Event loop
while(!glfwWindowShouldClose(window))
{
// Clear the screen to black
glClearColor(0.0f, 0.0f, 0.0f, 1.0f); glClear(GL_COLOR_BUFFER_BIT);
glfwSwapBuffers(window);
glfwPollEvents();
}
// Terminate GLFW
glfwTerminate(); return 0;
}
Unfortunately when I run the code I get an error code:
Thread 1: EXC_BAD_ACCESS (code = 1, address = 0x0).
It should appear a black screen with a dot in the center.

Answer 1

Multiple issues:
You're calling GL functions before you have a current GL context:
glGenVertexArrays(numVAOs,vao); // nope
glBindVertexArray(vao[0]); // nope
glUseProgram(renderingProgram); // nope
glDrawArrays(GL_POINT,0,1); // nope
// Create OpenGL window and context
GLFWwindow* window = glfwCreateWindow(1430, 800, "Davide", NULL, NULL);
glfwMakeContextCurrent(window);
Move those calls to after glfwMakeContextCurrent() (and your GL loader init) so they have a GL context to operate on (and check if window is NULL before using it in glfwMakeContextCurrent()):
// Create OpenGL window and context
GLFWwindow* window = glfwCreateWindow(1430, 800, "Davide", NULL, NULL);
// Check for window creation failure
if (!window)
{
// Terminate GLFW
glfwTerminate();
return 0;
}
glfwMakeContextCurrent(window);
glewExperimental = GL_TRUE; glewInit();
glGenVertexArrays(numVAOs,vao);
glBindVertexArray(vao[0]);
glUseProgram(renderingProgram);
glDrawArrays(GL_POINT,0,1);
You should also initialize renderingProgram before glUseProgram()ing it, perhaps with createShaderProgram()?
gl_Position isn't valid in a fragment shader. You're thinking of gl_Color or a user-defined output like your color output.
If you're requesting a GL 3.2 context then #version 430 isn't valid either. Either upgrade to GL 4.3 or downgrade your shaders to #version 150.
GL_POINT isn't a valid input to glDrawArrays(). You're thinking of GL_POINTS.
Call glDrawArrays() each frame instead of once at the beginning of your draw-loop so you have a chance to actually see your point.
GLSL statements require a semicolon after them.
Invalid:
void main(void)
{
gl_Position = vec4(0.0,0.0,0.0,1.0)
};
Valid:
void main(void)
{
gl_Position = vec4(0.0,0.0,0.0,1.0); // note the semicolon
} // note the lack of semicolon
All together:
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>
void CheckStatus( GLuint obj, bool isShader )
{
GLint status = GL_FALSE, log[ 1 << 11 ] = { 0 };
( isShader ? glGetShaderiv : glGetProgramiv )( obj, isShader ? GL_COMPILE_STATUS : GL_LINK_STATUS, &status );
if( status == GL_TRUE ) return;
( isShader ? glGetShaderInfoLog : glGetProgramInfoLog )( obj, sizeof( log ), NULL, (GLchar*)log );
std::cerr << (GLchar*)log << "\n";
std::exit( EXIT_FAILURE );
}
void AttachShader( GLuint program, GLenum type, const char* src )
{
GLuint shader = glCreateShader( type );
glShaderSource( shader, 1, &src, NULL );
glCompileShader( shader );
CheckStatus( shader, true );
glAttachShader( program, shader );
glDeleteShader( shader );
}
const char* const vert = 1 + R"GLSL(
#version 150
void main()
{
gl_Position = vec4(0.0,0.0,0.0,1.0);
}
)GLSL";
const char* const frag = 1 + R"GLSL(
#version 150
out vec4 color;
void main()
{
color = vec4(0.0,0.0,1.0,1.0);
}
)GLSL";
#define numVAOs 1
GLuint renderingProgram;
GLuint vao[ numVAOs ];
int main()
{
glfwInit();
// Define version and compatibility settings
glfwWindowHint( GLFW_CONTEXT_VERSION_MAJOR, 3 );
glfwWindowHint( GLFW_CONTEXT_VERSION_MINOR, 2 );
glfwWindowHint( GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE );
glfwWindowHint( GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE );
glfwWindowHint( GLFW_RESIZABLE, GL_FALSE );
// Create OpenGL window and context
GLFWwindow* window = glfwCreateWindow( 320, 240, "Davide", NULL, NULL );
// Check for window creation failure
if( !window )
{
// Terminate GLFW
glfwTerminate();
return 0;
}
glfwMakeContextCurrent( window );
glewExperimental = GL_TRUE;
glewInit();
glGenVertexArrays( numVAOs, vao );
glBindVertexArray( vao[ 0 ] );
GLuint renderingProgram = glCreateProgram();
AttachShader( renderingProgram, GL_VERTEX_SHADER, vert );
AttachShader( renderingProgram, GL_FRAGMENT_SHADER, frag );
glLinkProgram( renderingProgram );
CheckStatus( renderingProgram, false );
glUseProgram( renderingProgram );
// Event loop
while( !glfwWindowShouldClose( window ) )
{
// Clear the screen to black
glClearColor( 0.0f, 0.0f, 0.0f, 1.0f );
glClear( GL_COLOR_BUFFER_BIT );
glDrawArrays( GL_POINTS, 0, 1 );
glfwSwapBuffers( window );
glfwPollEvents();
}
// Terminate GLFW
glfwTerminate();
return 0;
}