Function set_heap_source 

pub fn set_heap_source(source: fn() -> usize) -> bool

Available on crate feature memory only.

Register a process-wide source of total live-heap bytes.

When set, every MemoryGuard switches its read path (current_bytes, pressure checks, and try_reserve admission) from the per-batch reservation counter to this source – a cheap, accurate, total-process heap figure that also catches growth the per-batch reservations never see (e.g. a transform ballooning a Vec).

Why a global hook and not a dependency: a tracking allocator must be the binary’s single #[global_allocator], which is the application’s choice, not a library’s – and rustlib is #![forbid(unsafe_code)], so it cannot implement one anyway. The application installs its allocator and wires it here in a few lines. This keeps rustlib allocator-agnostic with no allocator dependency in its graph.

The first call wins and returns true; later calls are a no-op and return false (the existing source is kept). Call once at startup, before constructing guards.

The application picks a tracking allocator – prefer an actively-maintained one such as tikv-jemalloc-ctl (stats.allocated); the cap crate also works but is effectively unmaintained (last release 2023).

// In the application binary, using jemalloc:
#[global_allocator]
static ALLOC: tikv_jemallocator::Jemalloc = tikv_jemallocator::Jemalloc;

fn main() {
    hyperi_rustlib::memory::set_heap_source(|| {
        tikv_jemalloc_ctl::epoch::advance().ok();
        tikv_jemalloc_ctl::stats::allocated::read().unwrap_or(0)
    });
    // ... build ServiceRuntime / MemoryGuard ...
}