Boost C++ Libraries: Ticket #7559: gcc-compatible symbol visibility not supported for clang

cc set

Tue, 23 Oct 2012 17:48:03 GMT

cc jonathan.jones@… added

Tue, 23 Oct 2012 22:56:52 GMT

Oops, the underscores in __attribute__ were taken as WikiFormatting.

Michel Morin — Wed, 24 Oct 2012 00:24:11 GMT

(In [81052]) Adding BOOST_SYMBOL_VISIBLE macro; refs #7559

Wed, 24 Oct 2012 01:01:39 GMT

Replying to michel:

(In [81052]) Adding BOOST_SYMBOL_VISIBLE macro; refs #7559

Is there a reason for not also defining BOOST_SYMBOL_EXPORT?

Michel Morin — Wed, 24 Oct 2012 01:23:02 GMT

Is there a reason for not also defining BOOST_SYMBOL_EXPORT?

I'll add BOOST_SYMBOL_EXPORT and BOOST_SYMBOL_IMPORT after collecting information about clang on the Windows platform. It will be done in a few days, I think.

Mathias Gaunard — Thu, 25 Oct 2012 12:26:38 GMT

on the Windows platform clang uses the code path in platform/win32.hpp. clang supports both __attribute__ and __declspec.

What I'd recommend is to put in compiler/clang.hpp the following

#if !defined(_WIN32) && !defined(__WIN32__) && !defined(WIN32))
#define BOOST_SYMBOL_EXPORT __attribute__((__visibility__("default")))
#define BOOST_SYMBOL_IMPORT
#define BOOST_SYMBOL_VISIBLE __attribute__((__visibility__("default")))
#endif

John Maddock — Thu, 25 Oct 2012 12:36:03 GMT

Just a note to say I'm aware of this issue, but as I'm not a Clang user I'd really like for someone to provide a patch that I can just blindly go ahead and apply...

Thanks, John Maddock.

Michel Morin — Thu, 25 Oct 2012 15:42:14 GMT

I was planning to add the following

//
// Dynamic shared object (DSO) and dynamic-link library (DLL) support
//
#if (defined(_WIN32) || defined(__WIN32__) || defined(WIN32)) && !defined(__CYGWIN__)
     // All Win32 development environments, including 64-bit Windows and MinGW, define
     // _WIN32 or one of its variant spellings. Note that Cygwin is a POSIX environment,
     // so does not define _WIN32 or its variants.
#  define BOOST_HAS_DECLSPEC
#else
#  define BOOST_SYMBOL_EXPORT __attribute__((__visibility__("default")))
#  define BOOST_SYMBOL_IMPORT
#endif
#define BOOST_SYMBOL_VISIBLE __attribute__((__visibility__("default")))

But I'd like to defer the support for the Windows platform, since there are some subtleties on that platform. I'm going to add BOOST_SYMBOL_EXPORT and BOOST_SYMBOL_IMPORT macros only on other platforms (i.e. the #else branch) for the meantime.

The #if condition in the above code is copied from config/compiler/gcc.hpp. John, do you know why !defined(__CYGWIN__) is needed? It looks verbose, since _WIN32 or its variants are not defined on cygwin.

Also, would it be nice to define BOOST_SYMBOL_IMPORT only on non-Windows platform , as mentioned by Mathias?

status changed; resolution set

Michel Morin — Fri, 26 Oct 2012 16:23:48 GMT

status new → closed
resolution → fixed

(In [81068]) Adding BOOST_SYMBOL_EXPORT and BOOST_SYMBOL_IMPORT; fixes #7559

Michel Morin — Fri, 26 Oct 2012 16:28:31 GMT

I chose to use Mathias' code

#if !defined(_WIN32) && !defined(__WIN32__) && !defined(WIN32)
#  define BOOST_SYMBOL_EXPORT __attribute__((__visibility__("default")))
#  define BOOST_SYMBOL_IMPORT
#  define BOOST_SYMBOL_VISIBLE __attribute__((__visibility__("default")))
#endif

rather than copying the code from config/compiler/gcc.hpp.