Item 2 of HANDOFF-x86-redef.md. C-x C-e and every value a break loop computes
are not a redefinition: there is no name to install a body into, so the
expression is wrapped in a function with nowhere to be called from and the
module says "run this once". flan_reload_call is that wrapper, and the agent
dlsyms exactly that spelling.
Its shape is emit_main's rather than a body's: no caller hands it a transfer
channel, so it owns a null cell on its own frame and passes that cell's address
on. Sixteen bytes of frame rather than eight, because rsp has to be 16-aligned
at the call and that is the whole of what the ABI asks of a frame making one.
The thunk itself is excluded from everything else the module does -- no cell, no
publish, no registry slot. There are 4096 slots and an expression evaluated in a
loop would exhaust them, and a module with nothing pointing into it is what lets
the agent unload it at all.
@flan_reload_transient is that claim, under emit.ml's three conditions. The
third is about data rather than text and is the one that can be got wrong in the
dangerous direction: a string literal lives in this module's image, an
expression may store one anywhere it likes, and a global left pointing into an
unmapped image is silent garbage rather than a fault. So the count is kept where
the literals are made -- string_const bumps the same Emit.m.nstr field emit.ml
counts on, and float constants, which are loaded and never retained,
deliberately do not. The install function's own registry name strings go through
string_const too, which is right rather than incidental: a module that interned
a name left something behind.
Joseph Ferano
5b1567c49f