free software for debugging shaders

Question

Are there any free software tools to debug GLSL shaders?

Answer 1

Just adding this answer for future readers:

On OS X, if you have the Developer Tools installed (a free download for the most current OS version), one of the many tools aside from Xcode is the OpenGL Shader Builder which :

[...] is a tool for developing and debugging programs for the graphics processing unit (GPU). It can help you visualize and preview shader objects without the complexity of surrounding code. [...] You can use the shader builder with programs written with OpenGL Shading Language or with older-style ARB vertex and fragment programs. OpenGL Shader Builder also supports geometry shaders, a recent addition to the OpenGL specification.

Emphasis added

Answer 2

Try glslDevil