Wireshark · Wireshark-dev: Re: [Wireshark-dev] Troubles with ASN generated code

[Guy Harris <guy@xxxxxxxxxxxx>]

On May 21, 2017, at 12:43 PM, Graham Bloice <graham.bloice@xxxxxxxxxxxxx> 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.

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

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.