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From: "imzhuli at vip dot qq.com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/53762] New: pointer-casts don't always check null-pointers Date: Sun, 24 Jun 2012 16:09:00 -0000 [thread overview] Message-ID: <bug-53762-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53762 Bug #: 53762 Summary: pointer-casts don't always check null-pointers Classification: Unclassified Product: gcc Version: 4.2.1 Status: UNCONFIRMED Severity: major Priority: P3 Component: c++ AssignedTo: unassigned@gcc.gnu.org ReportedBy: imzhuli@vip.qq.com Created attachment 27695 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27695 examples of lacking null-pointer check under these situations, null-pointers are not converted to null-pointers as the standard says; 1. with 'this' pointer: class A { public: int asomething; // important: if there's nothing in class A, the functions seems right; }; class B : public A { public: virtual ~B() {} void* thisoffset() { return static_cast<A*>(this); } void* offset() { B * pb = this; return static_cast<A*>(pb); } }; the two 'offset' function returns a 'offset of object of type A in objec of type B ', and a null-pointer. i think null-point should be right. 2. with reference from DERIVED class to BASE class: // class A & B defined as the above A* pa = NULL; B*pb = NULL; pa = &static_cast<A&>(*pb); ^^^^^^^^^^^^^^^^^^^^^^^^^^ will not perform null-pointer check; A* pa = NULL; B*pb = NULL; pa = static_cast<A*>(pb); ^^^^^^^^^^^^^^^^^^^^^^^^^ will perform null-pointer check;
next reply other threads:[~2012-06-24 16:09 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-06-24 16:09 imzhuli at vip dot qq.com [this message] 2012-06-24 16:26 ` [Bug c++/53762] " redi at gcc dot gnu.org 2012-06-24 16:31 ` redi at gcc dot gnu.org 2012-06-24 18:09 ` pinskia at gcc dot gnu.org
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