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Mention "extern types" on the opaque structs section #273

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Jun 18, 2021
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Mention "extern types" on the opaque structs section #273

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Mention "extern types" on the opaque structs section
JohnTitor Jun 9, 2021
538345a
Turn explanation into a sidenote
JohnTitor Jun 18, 2021
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10 changes: 8 additions & 2 deletions src/ffi.md
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Expand Up @@ -705,8 +705,14 @@ for more information.
# Representing opaque structs

Sometimes, a C library wants to provide a pointer to something, but not let you
know the internal details of the thing it wants. The simplest way is to use a
`void *` argument:
know the internal details of the thing it wants. The simplest way is to use "extern types".
But it's currently (as of June 2021) unstable and has some unresolved questions,
see the [RFC page][extern-type-rfc] and the [tracking issue][extern-type-issue] for more details.
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Hmm, instead of starting off with talking about something that is unstable and likely something people can't use, what do you think about moving into a side note? That is, take what you have written here, and move it down to the bottom of the page and make it a blockquote.

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Sounds good! Addressed via 538345a.


[extern-type-issue]: https://github.com/rust-lang/rust/issues/43467
[extern-type-rfc]: https://rust-lang.github.io/rfcs/1861-extern-types.html

Alternatively, we can use a `void *` argument:

```c
void foo(void *arg);
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