dlSharedLibraryLoader.cpp

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* Copyright (C) 2006, Novell, Inc. All rights reserved.
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#include "blocxx/BLOCXX_config.h"
#if defined(BLOCXX_USE_DL)
#include "blocxx/dlSharedLibraryLoader.hpp"
#include "blocxx/dlSharedLibrary.hpp"
#include "blocxx/Format.hpp"
#include "blocxx/GlobalString.hpp"
#include <dlfcn.h>

namespace BLOCXX_NAMESPACE
{

namespace
{
   GlobalString COMPONENT_NAME = BLOCXX_GLOBAL_STRING_INIT("blocxx.dlSharedLibraryLoader");
}
SharedLibraryRef
dlSharedLibraryLoader::loadSharedLibrary(const String& filename) const
{
   // There is a reason to use RTLD_NOW.  If some symbols can't be resolved because
   // the shared library is built incorrectly or missing some symbols or something,
   // then using RTLD_NOW will cause dlopen() to fail, and then the error can be detected
   // and handled.  If RTLD_LAZY is specified, dlopen() won't fail, but when code is
   // executed that tries to use an unresolvable symbol, that will cause a segfault.
   // RTLD_GLOBAL is necessary for proper exception and rtti support with gcc.
   // See http://gcc.gnu.org/faq.html#dso, so even though it may cause symbol conflicts,
   // we have to live with it.
   void* libhandle = dlopen(filename.c_str(), RTLD_NOW | RTLD_GLOBAL);
   
   String first_error = dlerror();
   String second_error;

#if defined(BLOCXX_USE_FAKE_LIBS)
   // This section, if it determines that a library is fake, will attempt
   // to load NULL (which, on most dlopen platforms should return a handle
   // to the main executable).  This handle can be used just like any
   // other, assuming that the main executable was linked with the proper
   // export flags (--export-dynamic on linux, -bexpall on AIX, etc.).
   if ( !libhandle )
   {
     if ( dlSharedLibrary::isFakeLibrary(filename) )
     {
       libhandle = dlopen(NULL, RTLD_NOW | RTLD_GLOBAL);
   
       if ( !libhandle )
       {
         second_error = dlerror();
       }
     }
   }
#endif /* defined(BLOCXX_USE_FAKE_LIBS) */   
   if (libhandle)
   {
      return SharedLibraryRef( new dlSharedLibrary(libhandle,
         filename));
   }
   else
   {
      Logger logger(COMPONENT_NAME);
      BLOCXX_LOG_ERROR(logger, Format("dlSharedLibraryLoader::loadSharedLibrary "
         "dlopen returned NULL.  Error is: %1", first_error));
      if ( !second_error.empty() )
      {
         BLOCXX_LOG_ERROR(logger, Format("dlSharedLibraryLoader::loadSharedLibrary (fakelib) "
            "dlopen returned NULL.  Error is: %1", second_error));      
      }
      return SharedLibraryRef( 0 );
   }
}

SharedLibraryLoaderRef
SharedLibraryLoader::createSharedLibraryLoader()
{
   return SharedLibraryLoaderRef(new dlSharedLibraryLoader);
}
dlSharedLibraryLoader::~dlSharedLibraryLoader()
{
}

} // end namespace BLOCXX_NAMESPACE

#endif // BLOCXX_USE_DL