And the advantage of this is, it can be whatever you need it to be. Always the same value, new value under certain conditions, consistent without ODR, your build requirements drive that.
Not a limited implantation of whatever it is you decide right now that the compiler must do.

From: Std-Proposals <std-proposals-bounces@lists.isocpp.org> on behalf of Thiago Macieira via Std-Proposals <std-proposals@lists.isocpp.org>
Sent: Friday, March 7, 2025 5:07:58 PM
To: std-proposals@lists.isocpp.org <std-proposals@lists.isocpp.org>
Cc: Thiago Macieira <thiago@macieira.org>
Subject: Re: [std-proposals] constexpr support for std::chrono::system_clock

On Thursday, 6 March 2025 23:03:16 Pacific Standard Time Tiago Freire via Std-
Proposals wrote:
> The simplest solution would be to just create a shell script that generates
> a file with the current time, let the build system call that shell script
> before build, and then not touch the compiler.

The drawback of that it that this does not obey $SOURCE_DATE_EPOCH (unless you
knew about it and coded your script that way), which in turn makes your code
non-reproducible. That adds to the workload of Linux distributions when trying
to figure out where the non-reproducibility came from.

That means there is an advantage of centralising this in the compiler.

--
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Principal Engineer - Intel DCAI Platform & System Engineering



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