HASH DOES NOT WORK. There are reasons for this in this thread, but they
boil down to this: you'd need to hash the entire reachable filesystem
because #include's don't resolve the same way depending on where the file
is accessed from on the filesystem.

#pragma once
#include "utils.h"

You'll see that header verbatim several times for different libraries in a
translation unit and you'll miscompile. HASH DOES NOT WORK.

On Mon, Sep 23, 2024 at 10:28 AM Frederick Virchanza Gotham via
Std-Proposals <std-proposals_at_[hidden]> wrote:

> On Mon, Sep 23, 2024 at 9:04 AM Ville Voutilainen wrote:
> >
> > That's completely irrelevant, the build machine's newline handling can
> > be whatever, as the content hash doesn't
> > need to be the same on different machines.
>
>
> I meant something like the following:
>
> Leonardo has his Apple laptop, and he checks out code to
> \\192.168.1.62\code\project1.
> Donatello has his MS-Windows laptop, and he checks out code to
> \\192.168.1.62\code\project2.
>
> So Leonardo and Donatello have all of their code checked out to the
> same network drive.
>
> In Donatello's project, he has a source file containing the line:
>
> #include "../project1/monkey.hpp"
>
> This header file has been checked out by Leonardo with Apple line
> endings. But Donatello also has his own copy of "monkey.hpp" in his
> own checkout, and one of Donatello's source files looks like this:
>
> #include "../project1/monkey.hpp"
> #include "common//monkey.hpp"
>
> So the first directive gets the header file with "\r\n" line endings,
> and the second directive gets it with "\n" line endings. And so if
> we're going to be taking the hash of file contents, I think best to
> normalise the line endings first (and also to remove trailing new line
> characters).
>
> Taking the hash of file contents might have too great an impact on
> compile times though. If compile time weren't an issue though, then I
> think taking the hash of file contents would be the optimal way to do
> "#pragma once".
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