Expand description
Proc-macro attribute expanding to a cfg-gated tool-attribute marker.
On a normal build cfg_attr is evaluated in the caller’s crate and the
no_alloc_check cfg is unset, so the whole attribute evaluates away:
no nightly features, no marker residue, no codegen impact. Under the
checker driver (--cfg no_alloc_check) it expands to
#[no_alloc_tool::root], legible only because the driver also passes
-Zcrate-attr=feature(register_tool) and
-Zcrate-attr=register_tool(no_alloc_tool).