log! macro fails when cross compiling with no_std

[zeonin]

I'm using a nightly rustc (1.8.0-nightly, ba356ffbc 2016-01-24) on an x86_64 linux system, and trying to cross compile liblog to i686. I'm able to compile libcore and liblog just fine, but when I try to use the log! macro, rust chokes.

Compiled with rustc -L $LIB_I686_DIR --target i686-unknown-linux-gnu temp.rs

temp.rs

Output:

<log macros>:1:37: 1:50 error: unresolved name `log::INFO` [E0425]
<log macros>:1 ( $ ( $ arg : tt ) * ) => ( log ! ( :: log:: INFO , $ ( $ arg ) * ) )
                                                   ^~~~~~~~~~~~~
<log macros>:1:29: 1:68 note: in this expansion of log! (defined in <log macros>)
temp.rs:36:5: 36:27 note: in this expansion of info! (defined in <log macros>)
<log macros>:1:37: 1:50 help: run `rustc --explain E0425` to see a detailed explanation
<log macros>:3:28: 3:42 error: unresolved name `log::DEBUG` [E0425]
<log macros>:3 let lvl = $ lvl ; ( lvl != :: log:: DEBUG || cfg ! ( debug_assertions ) ) &&
                                          ^~~~~~~~~~~~~~
<log macros>:5:24: 5:45 note: in this expansion of log_enabled! (defined in <log macros>)
<log macros>:1:29: 1:68 note: in this expansion of log! (defined in <log macros>)
temp.rs:36:5: 36:27 note: in this expansion of info! (defined in <log macros>)
<log macros>:3:28: 3:42 help: run `rustc --explain E0425` to see a detailed explanation
<log macros>:4:8: 4:26 error: unresolved name `log::log_level` [E0425]
<log macros>:4 lvl <= :: log:: log_level (  ) && :: log:: mod_enabled (
                      ^~~~~~~~~~~~~~~~~~
<log macros>:5:24: 5:45 note: in this expansion of log_enabled! (defined in <log macros>)
<log macros>:1:29: 1:68 note: in this expansion of log! (defined in <log macros>)
temp.rs:36:5: 36:27 note: in this expansion of info! (defined in <log macros>)
<log macros>:4:8: 4:26 help: run `rustc --explain E0425` to see a detailed explanation
<log macros>:4:35: 4:55 error: unresolved name `log::mod_enabled` [E0425]
<log macros>:4 lvl <= :: log:: log_level (  ) && :: log:: mod_enabled (
                                                 ^~~~~~~~~~~~~~~~~~~~
<log macros>:5:24: 5:45 note: in this expansion of log_enabled! (defined in <log macros>)
<log macros>:1:29: 1:68 note: in this expansion of log! (defined in <log macros>)
temp.rs:36:5: 36:27 note: in this expansion of info! (defined in <log macros>)
<log macros>:4:35: 4:55 help: run `rustc --explain E0425` to see a detailed explanation
<log macros>:6:1: 6:13 error: unresolved name `log::log` [E0425]
<log macros>:6 :: log:: log ( lvl , & LOC , format_args ! ( $ ( $ arg ) + ) ) } } )
               ^~~~~~~~~~~~
<log macros>:1:29: 1:68 note: in this expansion of log! (defined in <log macros>)
temp.rs:36:5: 36:27 note: in this expansion of info! (defined in <log macros>)
<log macros>:6:1: 6:13 help: run `rustc --explain E0425` to see a detailed explanation
<log macros>:4:1: 4:5 error: structure `log::LogLocation` has no field named `line`
<log macros>:4 line : line ! (  ) , file : file ! (  ) , module_path : module_path ! (  ) , }
               ^~~~
<log macros>:4:1: 4:5 help: did you mean `__line`?
<log macros>:4 line : line ! (  ) , file : file ! (  ) , module_path : module_path ! (  ) , }
               ^~~~
<log macros>:4:22: 4:26 error: structure `log::LogLocation` has no field named `file`
<log macros>:4 line : line ! (  ) , file : file ! (  ) , module_path : module_path ! (  ) , }
                                    ^~~~
<log macros>:4:22: 4:26 help: did you mean `__file`?
<log macros>:4 line : line ! (  ) , file : file ! (  ) , module_path : module_path ! (  ) , }
                                    ^~~~
<log macros>:4:43: 4:54 error: structure `log::LogLocation` has no field named `module_path`
<log macros>:4 line : line ! (  ) , file : file ! (  ) , module_path : module_path ! (  ) , }
                                                         ^~~~~~~~~~~
<log macros>:4:43: 4:54 help: did you mean `__module_path`?
<log macros>:4 line : line ! (  ) , file : file ! (  ) , module_path : module_path ! (  ) , }
                                                         ^~~~~~~~~~~
error: aborting due to 8 previous errors

When I do a pretty expansion, the info!() turns into this:

{
    static LOC: ::log::LogLocation =
        ::log::LogLocation{line: 36u32,
        file: "temp.rs",
        module_path: "temp",};
    let lvl = ::log::INFO;
    if {
        let lvl = lvl;
        (lvl != ::log::DEBUG || true) && lvl <= ::log::log_level() &&
            ::log::mod_enabled(lvl, "temp")
    } {
        ::log::log(lvl, &LOC,
                   ::core::fmt::Arguments::new_v1({
                       static __STATIC_FMTSTR:
                       &'static [&'static str]
                       =
                       &["Hello World!"];
                   __STATIC_FMTSTR
                   },
                   &match () {
                       () => [],
                   }))
    }
};

It looks like rust is stripping leading underscores within the log!() macro, and converting LogLevels into all caps.

[sfackler]

It looks like you're linking to rustc's internal liblog: https://github.com/rust-lang/rust/blob/master/src/liblog/lib.rs

[zeonin]

Interesting!

That log!() looks like what rust has been outputting, but the errors suggest that it's trying to link against this library, using the internal macros. Is there a way to disable or override a macro definition?

[zeonin]

Ah, the crate needs to be named something other than log, otherwise it attempts to pull in the macros from rust's internal liblog.

Thanks!