What is wrong with my shader initialization code? - c++

Question

I wrote this little function to init a shader while trying to get the hang of GLSL.
void createShader(string code, GLuint type) {
GLint success;
GLuint errorLogSize = 1024;
vector<GLchar> errorLog(errorLogSize);
cout << "trying to add shader, shader version is " << glGetString(GL_SHADING_LANGUAGE_VERSION) << " and opengl version is " << glGetString(GL_VERSION) << endl;
GLuint program = glCreateProgram();
GLuint obj = glCreateShader(type);
if (obj == 0) {
cout << "failed to create shader" << endl;
return;
} else {
cout << "created shader" << endl;
}
const GLchar* p = code.c_str();
GLint length = strlen(code.c_str());
cout << "trying to compile shader:" << endl << p << endl << "length: " << length << endl;
glShaderSource(obj, 1, &p, &length);
glCompileShader(obj);
glGetShaderiv(obj, GL_COMPILE_STATUS, &success);
if (success == 0) {
glGetProgramInfoLog(program, errorLogSize, NULL, &errorLog[0]);
cout << "error in shader compiling" << endl;
for (auto c : errorLog) cout << c;
cout << endl;
glGetShaderInfoLog(program, errorLogSize, NULL, &errorLog[0]);
for (auto c : errorLog) cout << c;
cout << endl;
}
glAttachShader(program, obj);
glLinkProgram(program);
glGetProgramiv(program, GL_LINK_STATUS, &success);
if (success == 0) {
glGetProgramInfoLog(program, errorLogSize, NULL, &errorLog[0]);
cout << "error in shader linking" << endl;
for (auto c : errorLog) cout << c;
cout << endl;
glGetShaderInfoLog(program, errorLogSize, NULL, &errorLog[0]);
for (auto c : errorLog) cout << c;
cout << endl;
}
glValidateProgram(program);
glGetProgramiv(program, GL_VALIDATE_STATUS, &success);
if (success == 0) {
glGetProgramInfoLog(program, errorLogSize, NULL, &errorLog[0]);
cout << "error in shader validating" << endl;
for (auto c : errorLog) cout << c;
cout << endl;
glGetShaderInfoLog(program, errorLogSize, NULL, &errorLog[0]);
for (auto c : errorLog) cout << c;
cout << endl;
}
glUseProgram(program);
}
I call it like this:
createShader("#version 150 out vec4 colorOut; void main() { colorOut = vec4(1.0, 0.0, 0.0, 1.0); }", GL_FRAGMENT_SHADER);
When I run the program it outputs this:
trying to add shader, shader version is 4.30 and opengl version is 4.4.12874 Compatibility Profile Context 14.100.0.0
created shader
trying to compile shader:
#version 150 out vec4 colorOut; void main() { colorOut = vec4(1.0, 0.0, 0.0, 1.0); }
length: 84
error in shader compiling
error in shader linking
Fragment shader(s) were not successfully compiled before glLinkProgram() was called. Link failed.
Fragment shader(s) were not successfully compiled before glLinkProgram() was called. Link failed.
error in shader validating
Fragment shader(s) were not successfully compiled before glLinkProgram() was called. Link failed.
Fragment shader(s) were not successfully compiled before glLinkProgram() was called. Link failed.
So pretty much all this tells me is that it can't compile. But I can't seem to find out why. I tried searching for similar situations (error in compilation but nothing in the log), but couldn't find anything relevant.
I expected this code to at least compile the shader. I used this guide as a guideline. The code I'm using is almost 1 on 1 copied from that guide. The only difference is they implemented it in two different functions and I added some extra error handling while trying to find out what's wrong with my code.
I'm using freeglut to init my window and I included, linked and initialized glew.

Answer 1

You need a newline character (\n) at the end of the #version 150. Everything starting with a # is a preprocessor directive, and the preprocessor operates line by line.
Change it to this, and it should work:
createShader("#version 150\n out vec4 colorOut; void main() { colorOut = vec4(1.0, 0.0, 0.0, 1.0); }", GL_FRAGMENT_SHADER);
You probably would have seen a more or less meaningful error message from the shader compiler, if there wasn't a minor mistake in the code that gets the shader info log:
glGetShaderInfoLog(program, errorLogSize, NULL, &errorLog[0]);
The first argument to glGetShaderInfoLog() is the shader, not the program. With the variable naming in the provided code, this should be:
glGetShaderInfoLog(obj, errorLogSize, NULL, &errorLog[0]);