The issue does not happen in gzdoom 4.7.1, nor with the other renderers. Attached a reproducible sample.
4.8.0-pre:

4.7.1:

Moderator: GZDoom Developers
Code: Select all
**** DIED WITH FATAL ERROR:
Shader 'test' could not be linked:
ERROR: Linking fragment stage: No function definition (body) found:
Process(vf4;