Scope issue with @static

[andreasnoack]

I'm seeing some weird interaction between cglobal and immutable inside @static.

These two are okay

module A
    @static if true
        const B = cglobal((:ompi_mpi_wchar, :libmpi))
    end
end

module A
    @static if true
        immutable T end
        const B = :B
    end
end

but

julia> module A
    @static if true
        immutable T end
        const B = cglobal((:ompi_mpi_wchar, :libmpi))
    end
end
WARNING: replacing module A
ERROR: error compiling anonymous: type definition not allowed inside a local scope

julia> versioninfo()
Julia Version 0.5.0-pre+5651
Commit 17c34e7* (2016-07-23 19:42 UTC)
Platform Info:
  System: Darwin (x86_64-apple-darwin15.6.0)
  CPU: Intel(R) Core(TM) i7-4870HQ CPU @ 2.50GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT NO_AFFINITY HASWELL)
  LAPACK: libopenblas64_
  LIBM: libopenlibm
  LLVM: libLLVM-3.7.1 (ORCJIT, haswell)

[yuyichao]

Dup of #2586

[andreasnoack]

@yuyichao Why is cglobal triggering the issue?

[vtjnash]

The at-static here is redundant and unnecessary (actually, it's pretty rare to need it)

[yuyichao]

Why is cglobal triggering the issue?

It's an intrinsic

[andreasnoack]

@vtjnash I think I have to use @static. The example here was just the smallest possible. In the real use case, I have to construct immutables to match C structs depending on which MPI implementation is linked. It's true that I can make the definitions with cglobal without the @static but then I need to repeat the same condition twice - once with @static and once without. Naively, I would expect that

module A
    @static if true
        immutable T end
        const B = cglobal((:ompi_mpi_wchar, :libmpi))
    end
end

and

module A
    immutable T end
    const B = cglobal((:ompi_mpi_wchar, :libmpi))
end

would be equivalent. Wouldn't that be desirable?

[vtjnash]

Sure, but note that the definition of @static is simply "evaluates the conditional at the toplevel scope", which is redundant where you are also evaluating the @static at the toplevel scope.

[yuyichao]

Wouldn't that be desirable?

Yes. But more fundamentally a @static block is equivalent to a normal block and you can reproduce the same bug with a normal block i.e. begin ... end. In any case, #2586 should clearly be fixed and this has nothing to do with @static at all.