aaron.ballman added inline comments.
================
Comment at: test/clang-tidy/readability-redundant-extern.cpp:37
+
+void another_file_scope(int _extern);
----------------
koldaniel wrote:
> aaron.ballman wrote:
> > More tests that I figured out:
> > ```
> > namespace {
> > extern void f(); // 'extern' is not redundant
> > }
> >
> > namespace a {
> > namespace {
> > namespace b {
> > extern void f(); // 'extern' is not redundant
> > }
> > }
> > }
> >
> > // Note, the above are consequences of http://eel.is/c++draft/basic.link#6
> >
> > #define FOO_EXTERN extern
> > typedef int extern_int;
> >
> > extern_int FOO_EXTERN foo(); // 'extern' is redundant, but hopefully we
> > don't try to fixit this to be '_int FOO_EXTERN foo();'
> >
> > // The above is a weird consequence of how specifiers are parsed in C and
> > C++
> > ```
> In the first two examples extern is redundant:
>
> "An unnamed namespace or a namespace declared directly or indirectly within
> an unnamed namespace has internal linkage. All other namespaces have external
> linkage."
>
> Also, based on the examples in http://eel.is/c++draft/basic.link#8 , the
> extern keyword has no effect in case of unnamed namespaces. In case of 'C'
> linkage defined by an extern keyword the checker does not warn.
>
> In the first two examples extern is redundant:
The `extern` keyword there isn't redundant, it's useless. When I hear
"redundant", I read it as "you can remove this keyword because the declaration
is already `extern`" but that's not the case there.
You are correct that the declarations retain internal linkage -- that's why I
think the `extern` keyword isn't redundant so much as it is confusing. We
already issue a diagnostic for this in the frontend, so I think we may just
want to silence the diagnostic here entirely. https://godbolt.org/z/WE6Fkd
WDYT?
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D33841/new/
https://reviews.llvm.org/D33841
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