Re: [boost] [filesystem] Epoch of trivial_clock

Subject: Re: [boost] [filesystem] Epoch of trivial_clock
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2014-08-22 08:00:29

On 22 Aug 2014 at 13:10, Bjorn Reese wrote:

> The filesystem::trivial_clock type is implementation-defined [1]. That
> means that the epoch is also implementation-defined.

Something which Bjorn discovered is that - believe it or not - POSIX 
leaves the epoch of time_t as implementation defined. That means that 
when you fetch a time_t from system_clock, it may, or may not, be 
using the epoch of other time_t's on the same system. I would assume 
in practice that when porting a STL to a platform the porter would 
make sure they align, but from a serialisation POV a never 
standardised epoch is a problem when moving data between systems. In 
other words, it is harder than it should be to write a timestamp to a 
file with an absolute guarantee it means the same thing to every 
reader.

Replies to Bjorn's question above may wish to bear this disjunct in 
mind when answering.

Niall

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