Re: Troubles with ASN generated code

[Graham Bloice <graham.bloice () trihedral com>]

On 21 May 2017 at 20:57, Guy Harris <guy () alum mit edu> wrote:

> On May 21, 2017, at 12:43 PM, Graham Bloice <graham.bloice () trihedral com>
> wrote:
>
> > I haven't looked at the specific issue, but Windows can export data from
> a DLL into another DLL.
>
> Yes, but if DLL A exports a data item called "fff" that's imported by DLL
> B, and DLL B uses it in this fashion:
>
>         static struct xyzzy foo {
>                 ...
>
>                 &fff,
>
>                 ...
>
>         };
>
> will that work?  You might be able to do
>
>         xxx = fff;
>
> but can you take the address of the exported item and use that to
> initialize a pointer in a static data structure.

It would appear not in a static initializer list. I can do it piecemeal,
e.g. foo.member = &fff.  BTW, I'm testing with VS2015.

If I try to assign &fff in an initialiser list I get an "error C2099:
initializer is not a constant".


> And will it work if DLL B is loaded at run time?

The piecemeal assignment does.  I've attached dlltest2.zip to show this.
 main.c is now compiled with no reference to dllimport.lib, i.e.

cl main.c dllexport.lib



> That's the specific issue here.
>
> > The data to be exported should be declared __declspec(dllexport),
>
> That's WS_DLL_PUBLIC_DEF from ws_symbol_export.h, if we're building for
> Windows with MSVC and WS_BUILD_DLL is defined.
>
> > and when it is required to be imported declared as __declspec(dllimport).
>
> That's WS_DLL_PUBLIC_DEF from ws_symbol_export.h, if  we're building for
> Windows with MSVC and WS_BUILD_DLL *isn't* defined.
>
> WS_DLL_PUBLIC is "WS_DLL_PUBLIC_DEF extern".
>
> So you *declare* data items, in header files, with WS_DLL_PUBLIC, and you
> *define* them, in source files, with WS_DLL_PUBLIC_DEF.
-- 
Graham Bloice

Attachment: dlltest2.zip
Description:

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