s_shader.h

/***********************************************************
* OpenGL shader load helper                                *
* no warranty implied | use at your own risk               *
* author: Andreas Mantler (ands) | last change: 13.04.2018 *
*                                                          *
* License:                                                 *
* This software is in the public domain.                   *
* Where that dedication is not recognized,                 *
* you are granted a perpetual, irrevocable license to copy *
* and modify this file however you want.                   *
***********************************************************/

static GLuint s_loadShader(GLenum type, const char *source)
{
	GLuint shader = glCreateShader(type);
	if (shader == 0)
	{
		fprintf(stderr, "Could not create shader!\n");
		return 0;
	}
	glShaderSource(shader, 1, &source, NULL);
	glCompileShader(shader);
	GLint compiled;
	glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
	if (!compiled)
	{
		fprintf(stderr, "Could not compile shader!\n");
		GLint infoLen = 0;
		glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLen);
		if (infoLen)
		{
			char* infoLog = (char*)malloc(infoLen);
			glGetShaderInfoLog(shader, infoLen, NULL, infoLog);
			fprintf(stderr, "%s\n", infoLog);
			free(infoLog);
		}
		glDeleteShader(shader);
		return 0;
	}
	return shader;
}

static GLuint s_loadProgram(const char *vp, const char *fp, const char **attributes, int attributeCount)
{
	GLuint vertexShader = s_loadShader(GL_VERTEX_SHADER, vp);
	if (!vertexShader)
		return 0;
	GLuint fragmentShader = s_loadShader(GL_FRAGMENT_SHADER, fp);
	if (!fragmentShader)
	{
		glDeleteShader(vertexShader);
		return 0;
	}

	GLuint program = glCreateProgram();
	if (program == 0)
	{
		fprintf(stderr, "Could not create program!\n");
		return 0;
	}
	glAttachShader(program, vertexShader);
	glAttachShader(program, fragmentShader);
    
    for (int i = 0; i < attributeCount; i++)
        glBindAttribLocation(program, i, attributes[i]);
    
	glLinkProgram(program);
	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);
	GLint linked;
	glGetProgramiv(program, GL_LINK_STATUS, &linked);
	if (!linked)
	{
		fprintf(stderr, "Could not link program!\n");
		GLint infoLen = 0;
		glGetProgramiv(program, GL_INFO_LOG_LENGTH, &infoLen);
		if (infoLen)
		{
			char* infoLog = (char*)malloc(sizeof(char) * infoLen);
			glGetProgramInfoLog(program, infoLen, NULL, infoLog);
			fprintf(stderr, "%s\n", infoLog);
			free(infoLog);
		}
		glDeleteProgram(program);
		return 0;
	}
	return program;
}