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Re: Documentation module lib-symbol-visibility

From: Дилян Палаузов
Subject: Re: Documentation module lib-symbol-visibility
Date: Fri, 20 Jul 2012 15:17:10 +0200
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:14.0) Gecko/20120713 Thunderbird/14.0

Hello Michael,

there is a point with dllexport/dllimport, however when not building for Windows, the argumentation does not apply and the recommendation for use LIBFOO_DLL_EXPORTED in the header files is suboptimal in my eyes.

Looking at the documentation of module lib-symbol-visibility, at the very end, I might oversee something, but I have the feeling, that when ./configure determined support for -fvisibility=hidden, and BUILDING_LIBFOO, HAVE_VISIBILITY and _MSC_VER are all defined, from

     #define LIBFOO_DLL_EXPORTED __attribute__((__visibility__("default")))
     #elif BUILDING_LIBFOO && defined _MSC_VER
     #define LIBFOO_DLL_EXPORTED __declspec(dllexport)
     #elif defined _MSC_VER
     #define LIBFOO_DLL_EXPORTED __declspec(dllimport)

follows, that LIBFOO_DLL_EXPORTED is
whereas it shall be
as declspec(dllexport) implies visibility(default), and visibility(default) does not help to DLL-export the symbols.

Със здраве

On 20.07.2012 14:15, Michael Goffioul wrote:
On Fri, Jul 20, 2012 at 12:56 PM, Дилян Палаузов
<address@hidden <mailto:address@hidden>> wrote:

    Defining LIBFOO_DLL_EXPORTED in public header files has no added
    value from the user's perspective: mentioning a function in the
    public header files implies, that the function is visible.  As
    suggested, there is another way to achieve the same result, without
    touching the header files.

One advantage I see for decorating declarations is easier compatibility
with compilers like MSVC that require exported variables to be decorated
with dllimport. From a C++ point of view, I'd also find easier to
decorate the class declaration once, instead of having to decorate all
members in the source code.


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