GL_SHADING_LANGUAGE_VERSION​
is different from
GL_SHADING_LANGUAGE_VERSION
the correct form is the second, taken from a compiler error, the first is text taken from
https://www.khronos.org/opengl/wiki/OpenGL_Context
(
	there is an invisible blank at the end of the first string, 
	it can be identified by moving the text cursor one step at the time​,
	it doesn't show through selection since it has width 0, but the cursor movement skips a step due to its presence )

verify by replacing in the following text:
this phrase GL_SHADING_LANGUAGE_VERSION
will change height on the screen depending on the label used 
and can also make the compiler fail with an absurd "undefined reference"