Segfault on glProgramUniform1i [closed] - c++

Question

Closed. This question needs debugging details. It is not currently accepting answers.
Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 8 years ago.
Improve this question
I'm trying to get screenWidth and screenHeight into my fragment shader through uniform variables. Here's my main.cpp where the offender lies, I can get the location (non -1) but when it actually sets the uniform variable thingy I segfault.
#include <GL/glew.h>
#include <GL/freeglut.h>
#include <stdio.h>
#include "math_3d.h"
#include "shader.h"
// Global
GLuint VBO;
static void RenderSceneCB()
{
glClear(GL_COLOR_BUFFER_BIT);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableVertexAttribArray(0);
glutSwapBuffers();
}
static void CreateVertexBuffer()
{
Vector3f Verticies[3];
Verticies[0] = Vector3f(-1.0f, -1.0f, 0.0f);
Verticies[1] = Vector3f(1.0f, -1.0f, 0.0f);
Verticies[2] = Vector3f(0.0f, 1.0f, 0.0f);
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(Verticies), Verticies, GL_STATIC_DRAW);
}
int main(int argc, char** argv)
{
const int SCREEN_WIDTH = 800, SCREEN_HEIGHT = 600;
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGBA);
glutInitWindowSize(SCREEN_WIDTH, SCREEN_HEIGHT);
glutInitWindowPosition(100, 100);
glutCreateWindow("Test Window");
glutDisplayFunc(RenderSceneCB);
GLenum res = glewInit();
if(res != GLEW_OK)
{
fprintf(stderr, "Error: '%s'\n", glewGetErrorString(res));
return 1;
}
const GLubyte* renderer = glGetString(GL_RENDERER);
const GLubyte* version = glGetString(GL_VERSION);
printf("Renderer: %s\n", renderer);
printf("Version: %s\n", version);
Shader vertexShader(GL_VERTEX_SHADER, "shader.vs");
Shader fragShader(GL_FRAGMENT_SHADER, "shader.fs");
GLuint program = glCreateProgram();
glAttachShader(program, vertexShader.shader);
glAttachShader(program, fragShader.shader);
glLinkProgram(program);
GLint status;
glGetProgramiv(program, GL_LINK_STATUS, &status);
if (status == GL_FALSE)
{
printf("No link\n");
}
glValidateProgram(program);
glGetProgramiv(program, GL_VALIDATE_STATUS, &status);
if (status == GL_FALSE)
{
printf("No validate\n");
}
glUseProgram(program);
printf("UNIFORM\n");
// Set uniform variables
GLint location = glGetUniformLocation(program, "screenWidth");
printf("loc: %d\n", location);
glProgramUniform1i(program, location, 800);
/*
GLint location2 = glGetUniformLocation(program, "screenHeight");
printf("loc: %d\n", location2);
glProgramUniform1i(program, location2, 600);
printf("uniform done\n");
*/
glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
glPointSize(10.0f);
CreateVertexBuffer();
glutMainLoop();
return 0;
}
The shader looks like this:
#version 130
uniform int screenWidth = 800;
uniform int screenHeight = 600;
out vec4 FragColor;
void main()
{
FragColor = vec4(gl_FragCoord.x/screenWidth, gl_FragCoord.y/screenHeight, 0.0, 1.0);
}

Answer 1

Your problem is actually that glProgramUniform1i (...) is relatively new. You have not come out and stated your OpenGL version explicitly, but your shader targets GLSL 1.30 (OpenGL 3.0) so chances are very good your implementation does not understand that function.
That function started out life in the Direct State Access extension (GL_EXT_direct_state_access), where it goes by the name glProgramUniform1iEXT (...) and was promoted to core when Separate Shader Objects were (GL 4.1).
The only difference between the two functions (glUniform1i (...) and glProgramUniform1i{EXT} (...)) is that one uses the currently bound program object, and the other lets you pass the one you need.

Answer 2

Changed how I set the uniform variables to this and everything worked out. I changed glProgramUniform1i to glUniform1i and took away the program parameter.
Here's the final main.cpp, look for the uniform section to see my changes.
#include <GL/glew.h>
#include <GL/freeglut.h>
#include <stdio.h>
#include "math_3d.h"
#include "shader.h"
// Global
GLuint VBO;
static void RenderSceneCB()
{
glClear(GL_COLOR_BUFFER_BIT);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableVertexAttribArray(0);
glutSwapBuffers();
}
static void CreateVertexBuffer()
{
Vector3f Verticies[3];
Verticies[0] = Vector3f(-1.0f, -1.0f, 0.0f);
Verticies[1] = Vector3f(1.0f, -1.0f, 0.0f);
Verticies[2] = Vector3f(0.0f, 1.0f, 0.0f);
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(Verticies), Verticies, GL_STATIC_DRAW);
}
int main(int argc, char** argv)
{
const int SCREEN_WIDTH = 800, SCREEN_HEIGHT = 600;
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGBA);
glutInitWindowSize(SCREEN_WIDTH, SCREEN_HEIGHT);
glutInitWindowPosition(100, 100);
glutCreateWindow("Test Window");
glutDisplayFunc(RenderSceneCB);
GLenum res = glewInit();
if(res != GLEW_OK)
{
fprintf(stderr, "Error: '%s'\n", glewGetErrorString(res));
return 1;
}
const GLubyte* renderer = glGetString(GL_RENDERER);
const GLubyte* version = glGetString(GL_VERSION);
printf("Renderer: %s\n", renderer);
printf("Version: %s\n", version);
Shader vertexShader(GL_VERTEX_SHADER, "shader.vs");
Shader fragShader(GL_FRAGMENT_SHADER, "shader.fs");
GLuint program = glCreateProgram();
glAttachShader(program, vertexShader.shader);
glAttachShader(program, fragShader.shader);
glLinkProgram(program);
GLint status;
glGetProgramiv(program, GL_LINK_STATUS, &status);
if (status == GL_FALSE)
{
printf("No link\n");
}
glValidateProgram(program);
glGetProgramiv(program, GL_VALIDATE_STATUS, &status);
if (status == GL_FALSE)
{
printf("No validate\n");
}
glUseProgram(program);
// Set uniform variables
GLint location = glGetUniformLocation(program, "screenWidth");
glUniform1i(location, 800);
GLint location2 = glGetUniformLocation(program, "screenHeight");
glUniform1i(location2, 600);
glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
glPointSize(10.0f);
CreateVertexBuffer();
glutMainLoop();
return 0;
}