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From: "matt at immute dot net" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/108732] New: Pre-compiled headers cannot be output to
 /dev/null
Date: Wed, 08 Feb 2023 21:59:34 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c
X-Bugzilla-Version: 12.2.0
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X-Bugzilla-Severity: normal
X-Bugzilla-Who: matt at immute dot net
X-Bugzilla-Status: UNCONFIRMED
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108732

            Bug ID: 108732
           Summary: Pre-compiled headers cannot be output to /dev/null
           Product: gcc
           Version: 12.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: matt at immute dot net
  Target Milestone: ---

with GCC 12, the following command fails with a fairly obscure error:

   $ gcc12.2.0 -c foo.h -o /dev/null
   foo.h:1: fatal error: cannot write PCH file: required memory segment
unavailable
   compilation terminated.

This also fails when invoked via g++. It works fine if the output is a norm=
al
file, and it always worked with previous GCC versions, so this is a pretty
surprising change.

This may seem like a strange thing to want to do, but I maintain a number of
builds that do similar invocations to verify that each header file is
self-contained.

Either way, I think it would be best to fix it, or if that's not possible, =
it
would be nice to improve the error message at the very least.=