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Re: RFC: Make dllimport/dllexport imply default visibility



On 03/07/2007, at 5:13 PM, Mark Mitchell wrote:


Geoffrey Keating wrote:

GCC's concept of visibility is very different to that of some other
compilers.

Yes, and that may be a problem. For some features, we want to have GNU
semantics that are consistent that across platforms; for others, we want
to match other compilers on a particular platform.

Yes. __attribute__((visibility)) has consistent GNU semantics, and other features (eg. -fvisibility-ms-compat, __dllspec) match other compilers.


To be clear, I don't have any objection to the semantics you stated,
from the point of view of first principles of language design. But,
they do not match existing practice on various systems -- and I consider
that a serious problem.

It's not possible for any semantics to match existing practise on every system, since systems differ. As I said, I think that it would be best for GCC to have one standard consistent set of semantics for __attribute__((visibility)), and then if it's desirable to match existing practise on other systems that should be done with other features explicitly labelled as such.


I hope you don't mean that there are other system's compilers using the '__attribute__((visibility))' syntax in a way that's incompatible with GCC. If there are, I think the appropriate response is a combination of fixincludes and a polite e-mail asking them to stop.

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