I've just read through this answer and its comments and have some related questions: Does this rule apply to uniform variables too? Can I call glUniform3fv for vec4 uniform and expect the W component to be 1.0, etc.? Where does the OpenGL spec mention about this topic?

Can I upload a vec3 value to vec4 uniforms?

I've just read through this answer and its comments and have some related questions:

Does this rule apply to uniform variables too?
Can I call glUniform3fv for vec4 uniform and expect the W component to be 1.0, etc.?
Where does the OpenGL spec mention about this topic?