Shader compile errors

Question

I am trying to compile a "garbage" shader, feeding in some garbage code to WebGL (see here for a fiddle):

gl = $('canvas')[0].getContext('experimental-webgl');

source = 'garbage12398sv;aa[]|\[12';

shader = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(shader, source);
gl.compileShader(shader);

console.log(gl.getError() === gl.NO_ERROR);

Surprisingly, gl.getError() === gl.NO_ERROR is true despite asking WebGL to compile some garbage.

Why doesn't getError flag an error? How can I get error information regarding the compilation status of my shaders?

Answer 1

gl.getError only returns errors for the OpenGL pipeline. A shader failing to compile does not cause an error in the pipeline. You can read about gl.getError here. You can query the status of shader like so:

var compiled = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
console.log('Shader compiled successfully: ' + compiled);
var compilationLog = gl.getShaderInfoLog(shader);
console.log('Shader compiler log: ' + compilationLog);

Similarly, shader program linking errors do not invalidate the OpenGL pipeline and can't be detected with gl.getError() you must call the object (shader, program, render buffer, etc) specific error query functions.