jberry 2005/02/21 21:57:21 Modified: c/src/xercesc/dom/impl DOMCasts.hpp Log: Bugfix: XERCESC-1074; get rid of warnings in newer gcc on offset calculations in DOMCasts.h ...hope I didn't break anybody... Revision Changes Path 1.4 +20 -5 xml-xerces/c/src/xercesc/dom/impl/DOMCasts.hpp Index: DOMCasts.hpp =================================================================== RCS file: /home/cvs/xml-xerces/c/src/xercesc/dom/impl/DOMCasts.hpp,v retrieving revision 1.3 retrieving revision 1.4 diff -u -r1.3 -r1.4 --- DOMCasts.hpp 8 Sep 2004 13:55:51 -0000 1.3 +++ DOMCasts.hpp 22 Feb 2005 05:57:21 -0000 1.4 @@ -75,6 +75,18 @@ // a second overloaded set that took and returned const arguements. // +// +// Note that using offsetof, or taking the offset of an object member at +// a 0 address, is now undefined in C++. And gcc now warns about this behavior. +// This is because doing do so is unreliable for some types of objects. +// See: http://gcc.gnu.org/ml/gcc/2004-06/msg00227.html +// : http://gcc.gnu.org/ml/gcc-bugs/2000-03/msg00805.html +// The casting code below works around gcc's warnings by using a dummy +// pointer, which the compiler cannot tell is null. The defeats the warning, +// but also masks the potential problem. +// The gcc option -Wno-invalid-offsetof may also be used to turn off this warning. +// + #include "DOMElementImpl.hpp" #include "DOMTextImpl.hpp" @@ -105,13 +117,15 @@ static inline DOMNode *castToNode(const DOMParentNode *p ) { - int parentOffset = (char *)&(((DOMElementImpl *)0)->fParent) - (char *)0; + DOMElementImpl* dummy = 0; + size_t parentOffset = (char *)&(dummy->fParent) - (char *)dummy; char *retPtr = (char *)p - parentOffset; return (DOMNode *)retPtr; } static inline DOMNode *castToNode(const DOMNodeImpl *p) { - int nodeImplOffset = (char *)&(((DOMElementImpl *)0)->fNode) - (char *)0; + DOMElementImpl* dummy = 0; + size_t nodeImplOffset = (char *)&(dummy->fNode) - (char *)dummy; char *retPtr = (char *)p - nodeImplOffset; return (DOMNode *)retPtr; } @@ -119,8 +133,9 @@ static inline DOMNodeImpl *castToNodeImpl(const DOMParentNode *p) { - int nodeImplOffset = (char *)&(((DOMElementImpl *)0)->fNode) - (char *)0; - int parentOffset = (char *)&(((DOMElementImpl *)0)->fParent) - (char *)0; + DOMElementImpl* dummy = 0; + size_t nodeImplOffset = (char *)&(dummy->fNode) - (char *)dummy; + size_t parentOffset = (char *)&(dummy->fParent) - (char *)dummy; char *retPtr = (char *)p - parentOffset + nodeImplOffset; return (DOMNodeImpl *)retPtr; }
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