Re: Fw: [cxx-abi-dev] Decimal Floating Point mangling was(Fw: [cxx-abi-dev] C++0x: Mangling of rvalue reference type)s
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Re: Fw: [cxx-abi-dev] Decimal Floating Point mangling was(Fw: [cxx-abi-dev] C++0x: Mangling of rvalue reference type)s
- To: Michael Wong <michaelw@xxxxxxxxxx>
- Subject: Re: Fw: [cxx-abi-dev] Decimal Floating Point mangling was(Fw: [cxx-abi-dev] C++0x: Mangling of rvalue reference type)s
- From: Sean Perry <perry@xxxxxxxxxx>
- Date: Mon, 20 Aug 2007 09:28:19 -0400
Are you trying to say that the C++ class type shall be binary compatible
with the C native type? That is going to fail immediately on parameter
passing and return values. And if we say that, then someone can throw a C
native type and catch it as the C++ class type. Similar odd behaviour
would happen with dynamic casting. The fact is that we have two different
types because C++ choose to implement decimal floating point as a class.
We need two different mangling schemes.
--
Sean Perry
Compiler Development
IBM Canada Lab
(905)-413-6031 (tie 969-6031), fax (905)-413-4839
Michael
Wong/Toronto/IBM
To
08/20/2007 08:23 Dennis Handly <dhandly@xxxxxxxxxx>
AM cc
cxx-abi-dev@xxxxxxxxxxxxxxxx,
premanand.rao@xxxxxx, Sean
Perry/Toronto/IBM@IBMCA
Subject
Re: Fw: [cxx-abi-dev] Decimal
Floating Point mangling was(Fw:
[cxx-abi-dev] C++0x: Mangling of
rvalue reference type)s(Document
link: Sean Perry)
I believe one of the point of an ABI is to settle on one type where there
are ambiguity or possible differences in choices. Otherwise, it is not an
ABI and there would be no interoperability.
So I agree with Dennis that having both types would be confusing. I have no
problem putting forward a case in the ABI document to support the native
DFP type choice. In fact, I believe this was one of the thing that Mark
Mitchell had asked me to do after coming up with a mangling scheme. I am
somewhat glad that we have converged to that same point of view.
Is this agreed?
Michael Wong
XL C++ Compiler kernel Development
IBM Canada Ltd., C2/KD2/8200/MKM
8200 Warden Avenue
Markham, Ontario L6G 1C7
W:905-413-3283 F:905-413-4839
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Dennis Handly <dhandly@xxxxxxxxxx> wrote on 08/17/2007 09:19:44 PM:
> >From: Sean Perry <perry@xxxxxxxxxx>
> >Yes, the native type and the standard class are different types.
>
> Then this may cause conflicts between the vendor's compiler and the
foreign
> devil compilers if they try to interoperate and each does it differently.
>
> I suppose an extern "C" interface would work to get around the mangling
> issues. At least for decimal. Complex may have other issues.