base_acc.txt

来自「开放源码的编译器open watcom 1.6.0版的源代码」· 文本 代码 · 共 41 行

Base class is inaccessible
==========================

struct A {
    int a;
};
struct B : A {
};
struct C : A, B {
};

void foo( C *p )
{
    p->a = 1;	// error: which A::a?
}

Borland, Microsoft, and CFRONT diagnose a problem with the class
definition for 'C'.  They generate a hard error describing that the
direct base class 'A' cannot be accessed because it is a base class of
'B'.  This is true in this example but all of the compilers should
diagnose ambiguous accesses of the base class 'A' or its member 'a'.
WATCOM C++ accepts the declaration but will diagnose any ambiguous use
of base class 'A'.  Unfortunately, the previously mentioned compilers
will not compile the following correct code:

struct A {
    static int a;
};
struct B : A {
};
struct C : A, B {
};

void foo( C *p )
{
    p->a = 1;	// OK: A::a is a static member
}

Any access to the static member 'a' is *not* ambiguous according to the
rules of the C++ language.  The WATCOM C++ compiler accepts this code.