Major upgrade to Boost.Config symbol visibility macros for shared libraries, based on patches from Jürgen Hunold with mods by Beman Dawes. Upgrade Boost.System to use the new visibility macros. Fixes #3697 and provides foundation for fixing 2114, 2309, etc.

[SVN r62140]

include/boost/config/compiler/borland.hpp

@@ -230,8 +230,9 @@
 //
 // all versions support __declspec:
 //
-#ifndef __STRICT_ANSI__
-#  define BOOST_HAS_DECLSPEC
+#if defined(__STRICT_ANSI__)
+// config/platform/win32.hpp will define BOOST_SYMBOL_EXPORT, etc., unless already defined  
+#  define BOOST_SYMBOL_EXPORT
 #endif
 //
 // ABI fixing headers:

include/boost/config/compiler/clang.hpp

@@ -18,12 +18,6 @@
 #  define BOOST_NO_RTTI
 #endif
 
-#if defined(__int32)
-// HACK: Clang only defines the type __int32 in Microsoft-compatibility mode,
-// which means that declspecs are also available
-#  define BOOST_HAS_DECLSPEC
-#endif
-
 #if defined(__int64)
 #  define BOOST_HAS_MS_INT64
 #endif

include/boost/config/compiler/codegear.hpp

@@ -147,8 +147,9 @@
 //
 // all versions support __declspec:
 //
-#if !defined(__STRICT_ANSI__)
-#  define BOOST_HAS_DECLSPEC
+#if defined(__STRICT_ANSI__)
+// config/platform/win32.hpp will define BOOST_SYMBOL_EXPORT, etc., unless already defined  
+#  define BOOST_SYMBOL_EXPORT
 #endif
 //
 // ABI fixing headers:

include/boost/config/compiler/gcc.hpp

@@ -108,6 +108,28 @@
 #if __GNUC__ > 3 || ( __GNUC__ == 3 && __GNUC_MINOR__ >= 1 )
 #define BOOST_HAS_NRVO
 #endif
+
+//
+// Dynamic shared object (DSO) and dynamic-link library (DLL) support
+//
+#if __GNUC__ >= 4
+#  if defined(_WIN32) || defined(__WIN32__) || defined(WIN32)
+     // 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
+#    define BOOST_SYMBOL_EXPORT __attribute__((dllexport))
+#    define BOOST_SYMBOL_IMPORT __attribute__((dllimport))
+#  else
+#    define BOOST_SYMBOL_EXPORT __attribute__((visibility("default")))
+#    define BOOST_SYMBOL_IMPORT
+#  endif
+#  define BOOST_SYMBOL_VISIBLE __attribute__((visibility("default")))
+#else
+// config/platform/win32.hpp will define BOOST_SYMBOL_EXPORT, etc., unless already defined  
+#  define BOOST_SYMBOL_EXPORT
+#endif
+
 //
 // RTTI and typeinfo detection is possible post gcc-4.3:
 //

include/boost/config/compiler/visualc.hpp

@@ -163,11 +163,6 @@
 #  define BOOST_NO_RTTI
 #endif
 
-//
-// all versions support __declspec:
-//
-#define BOOST_HAS_DECLSPEC
-
 //
 // C++0x features
 //

include/boost/config/platform/win32.hpp

@@ -21,10 +21,17 @@
 #  define BOOST_NO_SWPRINTF
 #endif
 
-#if !defined(__GNUC__) && !defined(BOOST_HAS_DECLSPEC)
+//  Default defines for BOOST_SYMBOL_EXPORT and BOOST_SYMBOL_IMPORT
+//  If a compiler doesn't support __declspec(dllexport)/__declspec(dllimport),
+//  its boost/config/compiler/ file must define BOOST_SYMBOL_EXPORT and
+//  BOOST_SYMBOL_IMPORT
+#ifndef BOOST_SYMBOL_EXPORT
 #  define BOOST_HAS_DECLSPEC
+#  define BOOST_SYMBOL_EXPORT __declspec(dllexport)
+#  define BOOST_SYMBOL_IMPORT __declspec(dllimport)
 #endif
 
+
 #if defined(__MINGW32__) && ((__MINGW32_MAJOR_VERSION > 2) || ((__MINGW32_MAJOR_VERSION == 2) && (__MINGW32_MINOR_VERSION >= 0)))
 #  define BOOST_HAS_STDINT_H
 #  define __STDC_LIMIT_MACROS

include/boost/config/suffix.hpp

@@ -25,6 +25,19 @@
 #ifndef BOOST_CONFIG_SUFFIX_HPP
 #define BOOST_CONFIG_SUFFIX_HPP
 
+//
+// ensure that visibility macros are always defined, thus symplifying use
+//
+#ifndef BOOST_SYMBOL_EXPORT
+# define BOOST_SYMBOL_EXPORT
+#endif
+#ifndef BOOST_SYMBOL_IMPORT
+# define BOOST_SYMBOL_IMPORT
+#endif
+#ifndef BOOST_SYMBOL_VISIBLE
+# define BOOST_SYMBOL_VISIBLE
+#endif
+
 //
 // look for long long by looking for the appropriate macros in <limits.h>.
 // Note that we use limits.h rather than climits for maximal portability,