https://issues.dlang.org/show_bug.cgi?id=20012

--- Comment #20 from Dennis <dkorpel@live.nl> ---
(In reply to anonymous4 from comment #16)
> Callbacks are more common than reflection-based dll exports.

Dplug has them: https://github.com/AuburnSounds/Dplug/blob/5ad0e4c512299fe8ea811ef2b041829f22f02a51/client/dplug/client/dllmain.d#L59

Excel-d has them: https://github.com/kaleidicassociates/excel-d/blob/ea7eb514e39e91fbc637e71a90d72614698dac18/source/xlld/wrap/traits.d#L234

It even mentions how "This used to be a template mixin but even using a string mixin inside fails to actually make it an extern(C) function.".

Can you give an example where the proposed behavior would be problematic?

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https://issues.dlang.org/show_bug.cgi?id=20012

--- Comment #21 from Dennis <dkorpel@live.nl> ---
(In reply to Walter Bright from comment #3)
> But there's another way you can do it:
> 
>   mixin template M()
>   {
>     export extern(C) pragma(mangle, "fun") void fun() {}
>   }
>   mixin M!();
> 
> which will work.

That works ad-hoc because C mangling is relatively easy, but it asks the user to maintain their own C mangling logic, while the compiler should (and does) provide that.

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https://issues.dlang.org/show_bug.cgi?id=20012

--- Comment #22 from anonymous4 <dfj1esp02@sneakemail.com> ---
(In reply to Dennis from comment #20)
> Can you give an example where the proposed behavior would be problematic?
Any callback. E.g. https://docs.microsoft.com/en-us/previous-versions/windows/desktop/legacy/ms633573%28v=vs.85%29

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https://issues.dlang.org/show_bug.cgi?id=20012

--- Comment #23 from Dennis <dkorpel@live.nl> ---
(In reply to anonymous4 from comment #22)
> (In reply to Dennis from comment #20)
> > Can you give an example where the proposed behavior would be problematic?
> Any callback. E.g. https://docs.microsoft.com/en-us/previous-versions/windows/desktop/legacy/ ms633573%28v=vs.85%29

We're specifically looking for a situation where:
1 you have a C-ABI callback-only function
2 but it's not anonymous
3 and it's in a mixin template
4 which is mixed in at global scope
5 and its name clashes with other extern(C) functions / you want to mix it in
multiple times

Has anyone ever made a mixin template that mixes in a non-anonymous WindowProc resulting in clashing names? So far this situation is only hypothetical, while there are numerous instances of users running into the situation where they want a C-mangled mixin template:

DPlug, Excel-D, this issue, https://issues.dlang.org/show_bug.cgi?id=962 and https://issues.dlang.org/show_bug.cgi?id=12575.

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https://issues.dlang.org/show_bug.cgi?id=20012

--- Comment #24 from anonymous4 <dfj1esp02@sneakemail.com> ---
AIU, Manu wants extern(C) to be mangled the same in all situations.

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https://issues.dlang.org/show_bug.cgi?id=20012

--- Comment #25 from Manu <turkeyman@gmail.com> ---
To be fair, what I think is that extern(C) should be mangled the same in all places that it's valid... Which is; global scope. extern(C) doesn't have any precedent outside of global scope, and I just don't care what it does in places where I don't consider it valid.

That said, if I had to choose, I'd say be the same everywhere. The odd guy out should be the explicit one.

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https://issues.dlang.org/show_bug.cgi?id=20012

Ethan Watson <gooberman@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |gooberman@gmail.com

--- Comment #26 from Ethan Watson <gooberman@gmail.com> ---
Bringing this over from my forum post.

Here's two code snippets.

export extern(C++) void fun() {}
pragma( msg, fun.mangleof );

----

mixin template M()
{
  export extern(C++) void fun() {}
}
mixin M!();
pragma( msg, fun.mangleof );

----

Both cases print the exact same mangle - _Z3funv on Linux, ?fun@@YAXXZ on Windows.

This illustrates two things:

1) extern(C++) behavior inside mixins is correct. extern(C) behavior is not.
2) pragma( mangle ) is not a catch-all workaround if you are compiling for
different architectures/operating systems with different ABIs

The Wikipedia article on name mangling[1] goes in to detail on the messy history of mangling C functions in the Windows ecosystem, if you're worried that using C++ as a counter-point is irrelevant.

[1] https://en.wikipedia.org/wiki/Name_mangling#C

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https://issues.dlang.org/show_bug.cgi?id=20012

Dlang Bot <dlang-bot@dlang.rocks> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull

--- Comment #27 from Dlang Bot <dlang-bot@dlang.rocks> ---
@dkorpel created dlang/dmd pull request #10236 "Fix issue 20012 - export inside mixin doesn't seem to work" fixing this issue:

- fix issue 20012 - export inside mixin doesn't seem to work

https://github.com/dlang/dmd/pull/10236

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https://issues.dlang.org/show_bug.cgi?id=20012

Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|export inside mixin doesn't |extern(C) functions inside
                   |seem to work                |template mixins are not
                   |                            |mangled as C functions

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https://issues.dlang.org/show_bug.cgi?id=20012

Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 OS|Windows                     |All

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