Re: "delete" asserts in debug build, multiple inheritance (msvc 7.1)

* Alf P. Steinbach:


[snip]


OK, a little investigation seems to indicate that the problem is related to
automatically generated default-initialization, not with virtual destructors as
I thought (although defining them or not had an effect).

<code>
struct Foo
{
#ifdef CF
     Foo() {}
#endif

#ifdef DF
     virtual ~Foo() {}
#endif
};

struct Naughty
{
#ifdef CN
     Naughty() {}
#endif

#ifdef DN
     virtual ~Naughty() {}
#endif
};

struct X: Naughty, Foo
{
#ifdef CX
     X(): Naughty(), Foo() {}
#else
     X() {}
#endif

#ifdef DX
     virtual ~X() {}
#endif
};

int main()
{
     X* p = new X;
     delete p; // !!! defined(CX) blows up with MSVC 7.1 debug build.
}
</code>

In matrix below, 0 means not defined, and 1 means defined.

<matrix>
     CF DF CN DN CX DX Blows up?
      0 0 0 0 0 0 no
      0 0 0 0 0 1 no
      0 0 0 0 1 0 YES
      0 0 0 0 1 1 no // anomalous
      0 0 0 1 0 0 no
      0 0 0 1 0 1 no
      0 0 0 1 1 0 YES
      0 0 0 1 1 1 YES
      0 0 1 0 0 0 no
      0 0 1 0 0 1 no
      0 0 1 0 1 0 YES
      0 0 1 0 1 1 no
      0 0 1 1 0 0 no
      0 0 1 1 0 1 no
      0 0 1 1 1 0 YES
      0 0 1 1 1 1 YES
      0 1 0 0 0 0 no
     (and I'm too lazy to continue)
</matrix>

which except for the entry marked "anomalous" seems to indicate that the blowup
is solely dependent on using explicit default initialization of base classes, as
with the constructor in the CX block of code.

This might just be a manifestation of MSVC 7.1's general problem with default
construction in initializer lists.

Anyway, it seems problem solved: I just leave that initialization unspecified,
and the compiler inserts the calls (I checked, it really does, as it should).

Cheers,

- Alf (angry with Bill, again)

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