FYI, as I get these I’ll direct them to std-proposals – this features alias is 
a bit harder for people to find and post to.

 

 

From: Michał W. Urbańczyk [mailto:[email protected]] 
Sent: Wednesday, June 28, 2017 12:47 PM
To: Herb Sutter <[email protected]>
Subject: Re: About p0697r0 — how SD-6 unclear status proved harmful to me

 

Absolutely, I'll post it there in a moment.

 

2017-06-28 21:32 GMT+02:00 Herb Sutter <[email protected] 
<mailto:[email protected]> >:

Thank you Michal. Would you be so kind as to post this to the std-proposals 
forum?

 

https://groups.google.com/a/isocpp.org/forum/?fromgroups#!forum/std-proposals 
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From: Michał W. Urbańczyk [mailto:[email protected] 
<mailto:[email protected]> ] 
Sent: Wednesday, June 28, 2017 10:47 AM
To: Herb Sutter <[email protected] <mailto:[email protected]> >
Subject: About p0697r0 — how SD-6 unclear status proved harmful to me

 

Hello,
I saw your recent paper on feature test macros (p0697r0) and I'd like to share 
my very recent experience in that matter as a plain C++ user — SD-6 presence 
and its unclear status proved harmful to me.

I wanted to port one of my projects to VS2017 — that eventually [1] led me to 
an issue within the Qt framework. It provides the "qOverload" variable template 
for compilers that support C++14 variable templates. The feature detection is 
based on SD-6 feature macro, so "qOverload" is not visible under MSVC, even 
though it supports variable templates. When I reported the issue to Qt 
mainteners, I was informed that not supporting VS there was an intentional 
choice to save on maintenance cost and that users should report it to MS to 
force them to implement SD-6. [2]

I feel like I've been catched in a crossfire between vendors who took different 
approaches towards SD-6 adoption. While it may be argued that either MS or Qt 
is at fault (respectively for not implementing useful SD-6 macros or for 
requiring non-standard feature), I think that problem should be finally solved 
by WG21, as you stated in p0697r0.

Both Qt framework and Visual Studio are vital parts of C++ ecosystem and not 
being able to fully used them together will likely be an increasing problem 
point, as C++14 and C++17 gains further adoption.

I hope you might find my story relevant with regards to to upcoming discussion 
on the SD-6 future.

Best regards,
Michał Urbańczyk


[1] Full discussion: https://github.com/woboq/verdigris/issues/6 
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[2] https://bugreports.qt.io/browse/QTBUG-61667?focusedCommentId=362506 
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&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-362506

 

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