Extern mod'd shared objects do not respect visibility of structs (linker errors)

[wilkie]

The following library, innocent enough, contains an allowed visibility conundrum:

// foo.rs
// Compiled with rustc --lib foo.rs
#[link(name = "foo", vers = "1.0", package_id = "foo")];

struct Foo { // ** should be public, but isn't, by human error ** //
  a: i8
}

impl Foo {
  pub fn bar(&self) {
  }
}

The following driver:

// bug.rs
// Compiled by rustc bug.rs -L.
extern mod foo;

fn main() {
  let f = foo::Foo { a: 0 };
  f.bar();
}

The compiler will believe Foo is public, and attempt to link the function bar (visible to the compiler, but not to the linker) causing the following linking error:

error: linking with `cc` failed: exit code: 1
note: cc arguments: '-m64' '-L/usr/local/lib/rustc/x86_64-unknown-linux-gnu/lib' '-o' 'bug' 'bug.o' '-Wl,--as-needed' '-L.' '-L/home/wilkie/rust-bug/.rust' '-L/home/wilkie/rust-bug' '-L/usr/local/lib/rustc/x86_64-unknown-linux-gnu/lib' '-lstd-6425b930ca146ae9-0.9-pre' '-L/usr/local/lib/rustc/x86_64-unknown-linux-gnu/lib' '-lrustuv-a13edc95d75df17-0.9-pre' '-L.' '-lfoo-167086a786d07119-1.0' '-lpthread' '-lrt' '-ldl' '-lm' '-lpthread' '-lstdc++' '-lmorestack' '-Wl,-rpath,$ORIGIN/../../../usr/local/lib/rustc/x86_64-unknown-linux-gnu/lib' '-Wl,-rpath,$ORIGIN/.' '-Wl,-rpath,/usr/local/lib/rustc/x86_64-unknown-linux-gnu/lib' '-Wl,-rpath,/home/wilkie/rust-bug'
note: bug.o: In function `main::h7f81f851c09f62ah::v0.0':
bug.rc:(.text+0x3d): undefined reference to `Foo::bar::hbf8f903627fe5f220fad::v1.0'
collect2: error: ld returned 1 exit status

error: aborting due to previous error

If I readelf -Ws libfoo-167086a786d07119-1.0.so, that exact symbol does exist with the correct hash.

If I put 'pub' in front of the struct definition, it works as expected.

I'm compiling a new version from master and will report later, but right now my rust --version is:

rustc 0.9-pre (3cc86d8 2013-12-05 12:32:12 -0800)
host: x86_64-unknown-linux-gnu

[alexcrichton]

I think you may just need to update your compiler, using today's version I get:

bar.rs:4:12: 4:20 error: struct `Foo` is private                                                                    
bar.rs:4     let f = foo::Foo { a: 0 };                                                                             
                     ^~~~~~~~                                                                                       
error: aborting due to previous error                                                                               

Which is what one would expect.

[wilkie]

Yep. Sorry about that. My build finished and it now reports an appropriate error. Must have been fixed recently. Thanks!