<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div>On May 29, 2012, at 3:57 AM, r4start wrote:</div><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000">This patch fixes the following problem:<br>
struct first {<br>
virtual void asdf() {}<br>
virtual void g(){}<br>
};<br>
<br>
struct second : virtual first {<br>
int q;<br>
virtual void asdf() { q = 90; }<br>
virtual void g(){ q = 12; }<br>
};<br>
<br>
struct third : virtual second {};<br>
void test2() { third *t; }<br>
<br>
In clang "second" has vtordisp for "first", but MSVC doesn`t
generate vtordisp for "first".<br>
According msdn " If a derived class overrides a virtual function
that it inherits from a virtual base class,<b> and if a constructor
or destructor for the derived class calls that function using a
pointer to the virtual base class</b>, the compiler may introduce
additional hidden "vtordisp" fields into classes with virtual bases.
".<br>
So in in this example "second" will not have vtordisp for "first".
But if we add constructor or destructor in "second" then MSVC add
vtordisp.<br></div></blockquote></div><br><div>Is this the rule used by MSVC? For example, does a vtordisp still get emitted even if a ctor "obviously" doesn't call any virtual functions, like if it's defined in the class definition and obviously empty? Please test both an empty ctor and an empty dtor.</div><div><br></div><div>Please also add testcases verifying that we do the right thing in further-derived classes that provide ctors. For example:</div><div> struct A { virtual void foo(); };</div><div> struct B : virtual A { virtual void foo(); }; // no vtordisp</div><div> struct Test1 : B { Test1(); };</div><div> struct Test2 : virtual B { Test2(); };</div><div> struct Test3 : B { Test3(); virtual void foo(); };</div><div> struct Test4 : virtual B { Test4(); virtual void foo(); };</div><div> </div><div>John.</div></body></html>