[cfe-dev] what libc++ version introduced C++14 delete operators?

René J. V. Bertin via cfe-dev cfe-dev at lists.llvm.org
Tue Dec 5 02:28:10 PST 2017


Marshall Clow via cfe-dev wrote:


Hi,

> An imperfect test would be checking _LIBCPP_VERSION and if it is greater
> than 1101, then it will have those calls.

Thanks, that's better than nothing.

> This has two drawbacks:
> * There will be versions of libc++ where _LIBCPP_VERSION == 1101 and the
> calls exist.

The application here is a GCC patch I'm working on (and off :)) to give it a -
stdlib=libstdc++|libc++ option. With older libc++ versions it appears to be 
possible to use GCC's static libsupc++ as a source for the missing operators. I 
presume that a trailing -lsupc++ linker argument will simply become a noop when 
libc++ already provided all dependencies. To be confirmed of course (and sadly I 
have no idea ATM how to write a test case.)

> * There *may* be customized versions of libc++ where vendors have decided
> to not ship those calls. (I don't know of any, but ...).

Why would vendors have done that? The only reason I can see is to allow a newer 
libc++ to be used with older clang versions that provided the operators 
implicitly, but such combinations shouldn't cause problems anyway, right?

R.



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