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http://issues.apache.org/jira/browse/XERCESC-1550?page=comments#action_12436513
]
Tommi Vainikainen commented on XERCESC-1550:
--------------------------------------------
Here is a patch for this problem. This problem also appears if you try to
compile your own software which links to Xerces with gcc -fvisibility=hidden
and use dynamic_cast for DOM types.
util/Compilers/GCCDefs.hpp
--- util/Compilers/GCCDefs.hpp.orig 2006-09-21 15:21:17.000000000 +0300
+++ util/Compilers/GCCDefs.hpp 2006-09-21 15:22:39.000000000 +0300
@@ -37,9 +37,14 @@
#define PLATFORM_EXPORT __declspec(dllexport)
#define PLATFORM_IMPORT __declspec(dllimport)
#else
+#if __GNUC__ >= 4
+#define PLATFORM_EXPORT __attribute__ ((visibility("default")))
+#define PLATFORM_IMPORT __attribute__ ((visibility("default")))
+#else
#define PLATFORM_EXPORT
#define PLATFORM_IMPORT
#endif
+#endif
// ---------------------------------------------------------------------------
// Indicate that we do not support native bools
> symbols visibility + inline virtual desctructors => dynamic_cast<DOMElement>
> failure in user code
> -------------------------------------------------------------------------------------------------
>
> Key: XERCESC-1550
> URL: http://issues.apache.org/jira/browse/XERCESC-1550
> Project: Xerces-C++
> Issue Type: Bug
> Components: Build
> Affects Versions: 2.7.0
> Environment: OSX GCC 4.0
> Reporter: Miklos Fazekas
>
> We have a code like this:
> XMLTest.cpp:
> DOMNodeList* nodes = doc->getElementsByTagName(L("TABLE"));
> if ( int i=nodes->getLength() == 1 )
> {
> DOMNode* att_node = nodes->item(0);
> DOMElement* att_element = dynamic_cast<DOMElement*>(att_node);
> printf ("Element:%d\n", att_element);
> }
> On OSX when we use symbols visibility attrbiutes, the dynamic_cast returns 0.
> The issue seems to be the following:
> 1. There is two RTTI entries generated for the class. [According to C++ the
> RTTI is generated at the place of the implementation of first virtual
> function.]
> 2. One RTTI entry is marked with visibility("hidden") and found in usercode.
> The other one is marked with visibility("default").
> 3. It seems that if there's an RTTI marked as "hidden" the dynamic_cast can't
> work. Quote from http://gcc.gnu.org/wiki/Visibility :
> " Symbol visibility is "default" by default but if it encounters just one
> definition with it hidden - just one - that typeinfo symbol becomes
> permanently hidden (remember the C++ standard's ODR - one definition rule).
> "
> class CDOM_EXPORT DOMElement: public DOMNode {
> public:
> ...
> virtual ~DOMElement() {};
> ...
> }
> Possible fixes:
> a.) Implement the destructor in a C++ file, compiled into xerces c++. This
> would avoid multiple RTTI .
> b.) set CDOM_EXPORT to visibility("default") even when it's used from the
> user code.
> We choose a.) as it seems to be a nicer solution.
> [By the way i do not see why symbols visibility of GCC should work that
> crappy with dynamic_cast, but there's not too much i could do there.]
> References:
> http://gcc.gnu.org/wiki/Visibility
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