Function firstfdhead_offset 

pub fn firstfdhead_offset() -> usize

Port of firstfdhead from Src/parse.c:3142 — C decl #define firstfdhead(f) ((FDHead) (((Wordcode) (f)) + FD_PRELEN)). Rust fn firstfdhead_offset returns the u32-word OFFSET of the first fdhead rather than a FDHead pointer. ) — pointer to the first struct fdhead past the prelude.