Re: libstdc++ PATCH to add abi tag to complex::real/imag

[Marc Glisse <marc dot glisse at inria dot fr>]

On Sat, 10 Nov 2012, Jason Merrill wrote:

> As mentioned in http://gcc.gnu.org/wiki/Cxx11AbiCompatibility, C++11 changes 
> the return type of complex::real and imag, leading to a binary 
> incompatibility between C++98 and C++11 code if the functions are used 
> without inlining.  This patch adds an ABI tag to the C++11 variants so that 
> they have different mangled names.  This does not change the exports from 
> libstdc++.

It looks like it won't prevent from using ref-qualifiers when they are 
implemented if we want to (PR 51013), which is good.

> For the map void->iterator change, I think it would make sense to just 
> unconditionally return an iterator;

It does break C++98 code that does "return f();" in a function returning 
void, but that's negligible.

> there's no binary compatibility issue 
> with older code that expects it to return void, the problem is only with 
> C++11 code calling a C++98 instantiation that returns void.

That's going to happen in practice, isn't it? So do you mean to add the 
abi tag to this unified function, for safety?

--
Marc Glisse