[Bug c++/53762] New: pointer-casts don't always check null-pointers
imzhuli at vip dot qq.com
gcc-bugzilla@gcc.gnu.org
Sun Jun 24 16:09:00 GMT 2012
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;
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