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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug pch/108732] Pre-compiled headers cannot be output to /dev/null
Date: Wed, 08 Feb 2023 22:45:48 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108732

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Matt Hellige from comment #3)
> As long as I'm updating builds, I'll switch to that invocation, thanks.
>=20
> I still do think it's a little odd that in this case (and *only* in this
> case?) output needs to be written to a mappable file.=20

The way PCH works is mapping files in and out for speed reasons. So it is n=
ot
really that odd. Even though it is not expliclty mentioned in the manual:
https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/Precompiled-Headers.html#Prec=
ompiled-Headers

The whole idea of PCH is that the file is mapped in with almost no changes =
done
afterwards so an exact dump of the memory from compiler can be loaded back =
in
without doing anything special; rather the OS handles the loading into memo=
ry
from the file.=