Hi all, I am writing a derive macro that I need to debug. I am trying to expand, but get an error[E0464]: multiple matching crates for
lazy_static. It looks like my toolchain has two lazy_static rlibs. How do I fix this?
Hi. I fallowed this tut https://blog.jfo.click/calling-a-c-function-from-rust/, and in end result Im still getting "note: /usr/bin/ld: cannot find -ldoubler.o". What could be the catch?
Full stack -> https://pastebin.com/rhb87wwC
P.S. the doubler.o is definitely there
@autokorrelationsfunktion update your Cargo.lock or check it to find which dependency you need to downgrade
@ozkriff downgrade? I did have two dependencies that used two different versions, but I updated them and the Cargo.lock only requires the current version now
Hmm, that's strange. Can you share your Cargo.lock (using some pastebin)?
Pls help :)
@ozkriff https://pastebin.com/zCFCbaUt
Yep, looks fine. Can you show the exact command and error message?
@trsh I'm not sure what's the problem, but it's usually done with
build.rs and cc crate in practice, like here - https://github.com/alexcrichton/rust-ffi-examples/tree/master/rust-to-c
@ozkriff https://pastebin.com/5Hm0Lem8
I read that too. Unfortunately, it sounds to me as if nobody knows what's going on...
Actually im trying to run c in rust
ahh those names ar confusing
Ok, good example, will go form there, tnx
@autokorrelationsfunktion Have you tried building it with Cargo?
@tanriol Yes. Currently, it does not compile when I use my derive macro and I do not understand why -- hence my want to expand the generated code
@autokorrelationsfunktion Try going via
cargo rustc -- -Z unstable-options --pretty expanded
I actually couldn't figure out how to properly specify which file I want to have expanded with that
so I just built a small project in which I have just one src/main.rs to test the macro
so I can solve the expansion for debugging the macro
but I still don't understand either how to use cargo rustc to expand single files nor why rustc has that problem with lazy_static
Your test requires the
lazy_static crate. IIUC, normally cargo provides special arguments to rustc to tell it where should the crates come from. You don't pass it, so rustc tries a fallback and fails due to multiple candidates it cannot choose between.
How do I tell rustc which lib to use?
Run
cargo build --verbose to see the full command line cargo uses
Ah, very nice. This helps, thank you!
when
1.26 is releasing ?
Release Dates
Rust 1.25 stable was released on Fri Mar 30 2018.
Rust 1.26 stable will be released on Fri May 11 2018.
Rust 1.27 stable will be released on Fri Jun 22 2018.
@ozkriff thnks.
I have another question. I am deriving a trait "HasX" for a type T. In my derive macro, I need to use lazy_static to generate a pub static ref. I would like this ref's name to be essentially T_X. How can I do that? I think I'd either need to define a new Ident (which I don't think is possible) or write something like "#T_X" in the quote, but that's not correct syntax.
IIUC, the
#var in quote! refers to a variable called var, so you probably need to introduce a variable for it.
Oh, nevermind, I just found https://github.com/dtolnay/quote and it has the answer...
but thanks a lot!
for some reason I didn't think to check quote's documentation
@ozkriff they should release a special version during rustfest.. will be fun :D
hey, I think I’ve found a rule I didn’t know it existed
is there some kind of rule forbidding “lifting up” of trait’s impl through safe coercion or auto-deref?
@phaazon What do you mean? Going from
&Trait to &Req when trait Trait: Req?
no
I mean something like, if you have a trait implemented on
&T, you cannot directly call that impl if you have a &mut T, while it safely coerce to &T
Hi, everybody know what kind of error is this? error[E0583]: file not found for module
i wanna use mod in schema.rs not main.rs
i try to call module like this
mod module_namein main.rs, it works, but not in schema.rs
The stable way is to have
main.rs
schema/mod.rs
schema/module_name.rs
but how i call a mod in another file? @tanriol
// main.rs
mod schema; // refers to schema/mod.rs
// schema/mod.rs
mod submodule; // refers to schema/submodule.rs
use schema::submodule::S as So; // note absolute path in `use`
const MY_S: submodule::S = So;
// schema/submodule.rs
pub(crate) struct S;
thanks for your help @tanriol