Hi everyone,
Currently, the keyword "extern" is highly overloaded. "extern" has the
following meanings:
1. "extern fn" in a type means "a function that closes over nothing" (at
least at one point; if this has already changed then disregard.)
2. "extern fn" in a declaration means "a function callable as a callback
from C to Rust". In this case the type is actually *u8, not "extern fn".
The latter means something completely different -- namely, (1) above --
a fact that causes numerous problems, including the inability to write
generic callbacks.
3. "extern mod foo { ... }" means "a module of C functions in a native
library called foo".
4. "extern mod foo;" means "link to the Rust crate named foo".
These multiple meanings of the keyword "extern" seem highly confusing.
To fix this, I propose the following changes:
(a) Fix #1 above by making the type of a Rust function that closes over
nothing simply "&static/fn(...) -> ...".
(b) Fix #2 above by making the type of such callbacks "extern fn(...) ->
...".
(c) Fix #4 by changing the syntax to link against a crate to something
else. I don't really have any opinions as to what the exact syntax
should be; the proposed "link" keyword seems like a fine choice, or
maybe something like "use lib".
Thoughts?
Patrick
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