gl_compile_program.cpp

#include "gl_compile_program.hpp"

#include <vector>
#include <string>
#include <stdexcept>
#include <iostream>

static GLuint gl_compile_shader(GLenum type, std::string const &source) {
	GLuint shader = glCreateShader(type);
	GLchar const *str = source.c_str();
	GLint str_length = GLint(source.size());
	glShaderSource(shader, 1, &str, &str_length);
	glCompileShader(shader);
	GLint compile_status = GL_FALSE;
	glGetShaderiv(shader, GL_COMPILE_STATUS, &compile_status);
	if (compile_status != GL_TRUE) {
		std::cerr << "Failed to compile shader." << std::endl;
		GLint info_log_length = 0;
		glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &info_log_length);
		std::vector< GLchar > info_log(info_log_length, 0);
		GLsizei length = 0;
		glGetShaderInfoLog(shader, GLint(info_log.size()), &length, &info_log[0]);
		std::cerr << "Info log: " << std::string(info_log.begin(), info_log.begin() + length);
		glDeleteShader(shader);
		throw std::runtime_error("Failed to compile shader.");
	}
	return shader;
}

GLuint gl_compile_program(
	std::string const &vertex_shader_source,
	std::string const &fragment_shader_source
	) {

	GLuint vertex_shader = gl_compile_shader(GL_VERTEX_SHADER, vertex_shader_source);
	GLuint fragment_shader = gl_compile_shader(GL_FRAGMENT_SHADER, fragment_shader_source);

	GLuint program = glCreateProgram();
	glAttachShader(program, vertex_shader);
	glAttachShader(program, fragment_shader);

	//shaders are reference counted so this makes sure they are freed after program is deleted:
	glDeleteShader(vertex_shader);
	glDeleteShader(fragment_shader);

	//link the shader program and throw errors if linking fails:
	glLinkProgram(program);
	GLint link_status = GL_FALSE;
	glGetProgramiv(program, GL_LINK_STATUS, &link_status);
	if (link_status != GL_TRUE) {
		std::cerr << "Failed to link shader program." << std::endl;
		GLint info_log_length = 0;
		glGetProgramiv(program, GL_INFO_LOG_LENGTH, &info_log_length);
		std::vector< GLchar > info_log(info_log_length, 0);
		GLsizei length = 0;
		glGetProgramInfoLog(program, GLint(info_log.size()), &length, &info_log[0]);
		std::cerr << "Info log: " << std::string(info_log.begin(), info_log.begin() + length);
		throw std::runtime_error("failed to link program");
	}

	return program;
}