[cfe-dev] Problem with gnu libc++ 4.7's chrono in Clang 3.2

[Howard Hinnant]

On Jan 3, 2013, at 11:36 AM, Martin Martin <martin at silverliningsystems.com> wrote:

> Hi,
> 
> Compiling the following 1-line file:
> 
> #include <condition_variable>
> 
> Causes the error:
> 
> $ clang++ -std=c++11 ./foo.cpp 
> In file included from ./foo.cpp:1:
> In file included from /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/condition_variable:37:
> /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/chrono:539:6: error: no matching constructor for
>       initialization of 'duration' (aka 'std::chrono::duration<long, std::ratio<1, 1000000> >')
>           : __d(__t.time_since_epoch())
>             ^   ~~~~~~~~~~~~~~~~~~~~~~
> /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/condition_variable:110:42: note: in instantiation of
>       function template specialization 'std::chrono::time_point<std::chrono::system_clock, std::chrono::duration<long,
>       std::ratio<1, 1000000> > >::time_point<std::chrono::duration<long, std::ratio<1, 1000000000> > >' requested here
>         const __clock_t::time_point __s_atime = __s_entry + __delta;
>                                                 ^
> /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/chrono:233:12: note: candidate constructor not viable: no
>       known conversion from 'duration<[...], ratio<[...], 1000000000>>' to 'duration<[...], ratio<[...], 1000000>>'
>       for 1st argument
>         constexpr duration(const duration&) = default;
>                   ^
> /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/chrono:239:23: note: candidate template ignored: couldn't
>       infer template argument ''
>           constexpr explicit duration(const _Rep2& __rep)
>                              ^
> /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/chrono:246:14: note: candidate template ignored: couldn't
>       infer template argument ''
>           constexpr duration(const duration<_Rep2, _Period2>& __d)
>                     ^
> /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/chrono:231:12: note: candidate constructor not viable:
>       requires 0 arguments, but 1 was provided
>         constexpr duration() : __r() { }
>                   ^
> 1 error generated.
> 
> Searching the web doesn't turn up anything related.
> 
> This is on Ubuntu 12.10, with Clang branches/release_32 compiled from source in release mode.
> 
> Any idea what I should look at next?

This doesn't look like a clang issue.  The condition_variable code is trying to truncate a time_point based on nanoseconds into one based on microseconds, and <chrono> won't let you do that implicitly.  This is a bug in the condition_variable code that <chrono> has found at compile time.

Howard