OpenGL not reporting shader compiler errors

Question

I'm having trouble getting OpenGL to work properly. It fails on all shaders and simply returns an info log with the length of 0.

To see if it was in fact OpenGL, I created a little piece of code to test it:

GLuint s = glCreateShader(GL_VERTEX_SHADER);

const char *src = "bad\nsource\ncode";

glShaderSource(s, 1, &src, 0);

GLint len;
glGetShaderiv(s, GL_INFO_LOG_LENGTH, &len);

std::vector<char> buffer(len+1);
glGetShaderInfoLog(s, len, 0, buffer.data());
buffer[len] = '\0';

std::cout << len << std::endl;

std::cout << buffer.data() << std::endl;

And when ran, it simply prints 0 to the console.

What's happening?

dav1d · Accepted Answer · 2016-02-13 10:24:17Z

4

You need to compile your shader in order to get an errorlog.

Pseudo Code:

glCompileShader(shader);

GLint status;
glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
if(status == GL_FALSE) {
    GLint infolog_length;
    glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infolog_length);

    GLchar[] infolog = new GLchar[infolog_length+1];
    glGetShaderInfoLog(shader, infolog_length, null, infolog.ptr);

    // print infolog etc.
}

From The Documentation:

glGetShaderInfoLog returns the information log for the specified shader object. The information log for a shader object is modified when the shader is compiled. The string that is returned will be null terminated.

answered Feb 13, 2016 at 10:24

dav1d

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3 Comments

user112513312 Over a year ago

The failure to call glCompileShader was actually a mistake in my test code (absent in the real code) that I didn't catch. But at least I know now OpenGL isn't broken. Interestingly enough, I did call compile on my actual shaders, but the mistake was due certain constructors not working right and resulting in the shaders not being initialized properly.

peppe Over a year ago

Side note: you can (should?) get the info log even when compilation succeeds. For instance, the driver can put warnings in there.

derhass Over a year ago

another side note: GL implementations are not required to put anything into the info logs, even when compilation/linking fails, so always returning a log size of 0 bytes would still be compliant to the spec.

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