[PATCH] Define new filesystem::__file_clock type

[Jonathan Wakely]

On 05/01/19 20:03 +0000, Jonathan Wakely wrote:
>In C++17 the clock used for filesystem::file_time_type is unspecified,
>allowing it to be chrono::system_clock. The C++2a draft requires it to
>be a distinct type, with additional member functions to convert to/from
>other clocks (either the system clock or UTC). In order to avoid an ABI
>change later, this patch defines a new distinct type now, which will be
>used for std::chrono::file_clock later.
>
>	* include/bits/fs_fwd.h (__file_clock): Define new clock.
>	(file_time_type): Redefine in terms of __file_clock.
>	* src/filesystem/ops-common.h (file_time): Add FIXME comment about
>	overflow.
>	* src/filesystem/std-ops.cc (is_set(perm_options, perm_options)): Give
>	internal linkage.
>	(internal_file_lock): New helper type for accessing __file_clock.
>	(do_copy_file): Use internal_file_lock to convert system time to
>	file_time_type.
>	(last_write_time(const path&, error_code&)): Likewise.
>	(last_write_time(const path&, file_time_type, error_code&)): Likewise.
>
>Tested powerpc64-linux, committed to trunk.

There's a new failure on 32-bit x86:

/home/jwakely/src/gcc/gcc/libstdc++-v3/testsuite/27_io/filesystem/operations/last_write_time.cc:148: void test02(): Assertion 'approx_equal(last_write_time(f.path), time)' failed.
FAIL: 27_io/filesystem/operations/last_write_time.cc execution test

I'll deal with that ASAP.