Having the ability to detect the variant seems useful.   The ABI tweaks that ARM uses does become visible to the ABI support library (e.g. __cxa_guard_*).  Having the ability to detect the variant would permit additional flexibility and permit that the runtime validate that the variant matches.

I don't have a suggestion on how to represent the variant information however.

On Fri, Jan 6, 2017 at 7:54 PM Richard Smith <richard@metafoo.co.uk> wrote:
I think it makes sense to have semi-standard macros for this, and while these aren't standard features I think SD-6 could be an OK home for them. 

Do you anticipate needing any way to detect abi variants (eg, ARM ABI is itanium with tweaks)?

I think some kind of version could be useful for both macros, but that could be added later.

On 6 Jan 2017 5:45 pm, "Saleem Abdulrasool" <compnerd@compnerd.org> wrote:
Hi,

I was wondering if it would be possible to add a macro to identify the underlying ABI that the C++ runtime is using?  Although itanium is the more popular choice, there are alternative ABIs such as the one which Microsoft uses.  I would propose something like the following:

__cpp_abi_itanium
__cpp_abi_microsoft

They would be defined to 1 based on which is being used.  This would allow the implementation to change the behavior based on the ABI being used.

Thanks!

-- 
Saleem Abdulrasool
compnerd (at) compnerd (dot) org



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