Macro declare_jemalloc_conf 

macro_rules! declare_jemalloc_conf {
    () => { ... };
}

Declares the _rjem_malloc_conf symbol jemalloc’s conf.c resolves at precedence 1 (weaker than _RJEM_MALLOC_CONF, stronger than the compile-time --with-malloc-conf default), pointing it at CONF.

Must be invoked from a binary crate, immediately below its #[global_allocator] static: jemalloc’s C code defines _rjem_malloc_conf as a weak definition, so nothing forces the linker to pull our override out of an rlib – only a binary’s own object files are always linked in full. $crate (rather than a bare CONF) is required because this macro expands inside each calling binary crate, not inside telemetry-sink.