Date: Tue, 26 Apr 2022 17:48:00 -0700 From: Mark Millard <marklmi@yahoo.com> To: joerg@bec.de, FreeBSD Hackers <freebsd-hackers@freebsd.org> Cc: jbo@insane.engineer Subject: Re: llvm & RTTI over shared libraries Message-ID: <A7BF3192-44EF-485C-8CB7-E7F4FFCA1E5A@yahoo.com> References: <A7BF3192-44EF-485C-8CB7-E7F4FFCA1E5A.ref@yahoo.com>
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=E2=80=A2 Joerg Sonnenberger <joerg_at_bec.de> wrote on
=E2=80=A2 Date: Tue, 26 Apr 2022 23:47:23 UTC :
> Am Mon, Apr 25, 2022 at 03:39:48PM -0700 schrieb Mark Millard:
> > Basically I avoid inline definitions of:
> >=20
> > virtual ~type_base();
> > virtual ~type_int();
> > virtual ~type_string();
>=20
> You only need to ensure that the class has one non-pure non-inline
> function.
I'm confused at what you are claiming that I did wrong or
described incorrectly for the example at hand. Those are 3
separate classes each with one virtual method that is not
in line (and that I showed the definitions for later in
the message). No other such functions were involved explicitly
in those 3 classes.
The gcc class type_info in /usr/local/lib/gcc11/include/c++/typeinfo
describes this implementation detail for type_info itself, as its
example, via:
class type_info
{
public:
/** Destructor first. Being the first non-inline virtual function, =
this
* controls in which translation unit the vtable is emitted. The
* compiler makes use of that information to know where to emit
* the runtime-mandated type_info structures in the new-abi. */
virtual ~type_info();
. . .
> That's the key function and determines the translation unit
> (and by extension the DSO) where the virtual table and the typeinfo is
> placed.
I'm a again confused about where the above disagrees with
what I wrote (in text that you did not quote).
> If there is no such function, both will be defined as weak
> mergable symbol and that will not result in a unique address when =
using
> RTLD_LOCAL.
I was certainly less detailed about how multiple definitions
are handled. Was that your point?
Let me know if I've missed some import point --or made some
stupid screwup in what I'd written.
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
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