Function crate_prefix 

pub(crate) fn crate_prefix() -> String

The consuming crate’s name, used as the prefix for every macro-emitted #[no_mangle] C symbol.

Reads CARGO_CRATE_NAME, which cargo sets (with hyphens already normalized to underscores) for the rustc invocation that expands this proc macro — the same precedent miniextendr_init!() relies on (lib.rs, miniextendr_init fn). Real macro expansion (i.e. compiling a downstream crate through cargo) always has this set.

Falls back to CARGO_PKG_NAME (normalized the same way, since it is not auto-normalized) for the one context where CARGO_CRATE_NAME is absent: this crate’s own unit/insta tests call codegen functions directly at test runtime rather than through real macro expansion, and cargo does not forward CARGO_CRATE_NAME to a test binary’s process environment (verified empirically — only CARGO_PKG_* vars are). Falls back further to the literal "crate" if even that is absent (e.g. a direct rustc invocation bypassing cargo entirely).