What does “statically assign” mean for gl_FragDepth?

问题

The documentation for gl_FragDepth, contains the phrase "If a shader statically assigns to gl_FragDepth... ." What does "statically" mean?

回答1:

GLSL ES 1.00 specification

7.2 Fragment Shader Special Variables

(A shader contains a static assignment to a variable x if, after pre-processing, the shader contains a statement that would write to x, whether or not run-time flow of control will cause that statement to be executed.)

来源：https://stackoverflow.com/questions/43218221/what-does-statically-assign-mean-for-gl-fragdepth