Re: [preprocessor] Dropping support for compilers that do not implement variadic macros

From: Edward Diener (eldiener_at_[hidden])
Date: 2020-09-15 15:09:12

On 9/15/2020 6:01 AM, Andrey Semashev via Boost wrote:
> On 2020-09-15 05:18, Edward Diener via Boost wrote:
>> On 9/14/2020 7:38 PM, Andrey Semashev via Boost wrote:
>>>
>>> Boost.Preprocessor is used quite a lot throughout Boost, not in the 
>>> least part specifically to support C++03. If it stops being C++03 
>>> compatible, this will mean most of Boost will stop as well.
>>
>> My proposed change does not mean that PP stops supporting C++03. Lots 
>> of compilers supported variadic macros even when compiling in C++03 
>> mode, ie. gcc and clang and vc++ starting with VS2005 being the most 
>> prominent. The few that actually did not support variadic macros in 
>> C++03 mode should not be used with future Boost by anybody; they are 
>> really ancient.
> 
> Ok, so it doesn't look as scary as it initially did. Thank you.
> 
>> Isn't that what discouraging compiling in C++03 mode is all about, so 
>> that ancient compilers still supporting c++03 should not be used by 
>> developers as Boost goes forward.
> 
> I actually don't know what the incentive to actively drop C++03 is.
> 
> (Disclosure: I write C++17 on a daily basis and I realize C++03 is 
> limiting in some ways. It is not in others, and some written code can be 
> made trivially compatible with C++03. Granted, this may not be the case 
> with Boost.PP, but that code is already written and I suspect requires 
> little maintenance.

It will make Boost PP code much cleaner to understand if support for 
non-variadic macros is dropped. I still will keep whatever workarounds 
are needed for the VC++ non-standard default preprocessor. Now that 
Microsoft has a new C++ standard preprocessor, hopefully programmers 
will switch to it and those old workarounds can also go away some day.

> Also, in my C++17 code base I'm using some great 
> C++03 libraries, including Boost, and I see nothing wrong about it. 
> Please, don't consider this paragraph as an invitation to C++03 vs. 
> C++11 argument.)