Re: [PATCH, 3/4] Enable libstdc++ as a DLL on windows platforms.

[Kai Tietz <ktietz70 at googlemail dot com>]

2009/7/18 Dave Korn <dave.korn.cygwin@googlemail.com>:
> Kai Tietz wrote:
>> 2009/7/18 Dave Korn <dave.korn.cygwin@googlemail.com>:
>>> Kai Tietz wrote:
>>>
>>>> Well, my concerns here are more in a general way of users using gcc
>>>> for compiling source code written for windows. Believe me there are
>>>> many projects (like mozilla, reactos, boehm-gc, ...) which want to
>>>> compile their sources with VS and gcc. For those users the mis-use (in
>>>> their opinion) of the _DLL macro is very annoying. This was the reason
>>>> why I have the strong opinion here, that gcc shouldn't use this macro
>>>> for win32 targets.
>>> ?Well, surely if they're compiling for MSVC using -D_DLL in order to get the
>>> DLL version of the runtime libs, when they compile under GCC they will also
>>> want to get the DLL version of the runtime libs? ?(Ideally their configure
>>> scripts will define it or not according to --enable/disable-static/shared?) ?I
>>> don't quite see why it would be misuse to make the GCC toolchain respond to
>>> -D_DLL in the same way as the MSVC one, and isn't that what would result in
>>> this case?
>> You miss the point that VC defines _DLL automatically. This macro
>> isn't user controlled. It is a builtin macro, like __FILE__, or
>> _WIN32. The problem occurs, when users want to include headers from a
>> library using _DLL for making decisions about dllimport or static API.
>
> ?Ok, so should MinGW un/define _DLL automatically using a builtin predefine
> or spec option, based on whether static or shared linking is in use?
> Presumably any such library that uses _DLL in its headers must be happy with
> the import/no-import decision being made on the same basis as the
> shared/static runtime decision, since it uses the same symbol that the MS
> language runtime uses?

Well, IMHO it better to have specific defines in each header-set to
specify, if static or shared is wanted. And mingw.org should add to
their headers the define of _DLL to always true, as it imitates VC
best. Otherway would be here to add this to target itself and
auto-define it, but well this shouldn't correct in all cases. E.g.
Wine provides a MS like C-runtime and if they are providing a static
version of it, too, then the definition of _DLL would be wrong here.

Cheers,
Kai


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