[Bug c++/94843] New: if i use pch and specify '-include' twice compilation fails

[Bug c++/94843] New: if i use pch and specify '-include' twice compilation fails

[m+gccbugs at gshep dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94843

            Bug ID: 94843
           Summary: if i use pch and specify '-include' twice compilation
                    fails
           Product: gcc
           Version: 9.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: m+gccbugs at gshep dot ru
  Target Milestone: ---

Hi!

The following commands give "cc1plus fatal error ./empty.h No such file or
directory ; compilation terminated."

=========================================

mkdir 111
touch 111/empty.h
echo 'int main(){ return 0; }' > a.cpp
find
g++ -g -Winvalid-pch -x c++-header -o empty.h.gch -c 111/empty.h
g++ -I. -I111 -g -Winvalid-pch -include empty.h -include empty.h -o a.o -c
a.cpp

=========================================

We encountered this issue on our project except that we have 'include
"empty.h"' in cpp source file and one '-include' command line parameter.

Is this a bug or am I missing anything? Thanks in advance.

[Bug c++/94843] if i use pch and specify '-include' twice compilation fails

[m+gccbugs at gshep dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94843

--- Comment #1 from gccshep <m+gccbugs at gshep dot ru> ---
environment:

$ uname -a
Linux 5user6-7VirtualBox890 5.3.0-46-generic #38~18.04.1-Ubuntu SMP Tue Mar 31
04:17:56 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

tested with g++-8/9 :
$ g++-8 --version
g++-8 (Ubuntu 8.4.0-1ubuntu1~18.04) 8.4.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ g++-9 --version
g++-9 (Ubuntu 9.3.0-11ubuntu0~18.04.1) 9.3.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

It seems like it is reproducible with gcc too.

Also reproduced this with gcc/++ 5.5.0 on Slackware 64.

[Bug pch/94843] if i use pch and specify '-include' twice compilation fails

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94843

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c++                         |pch
           Keywords|                            |diagnostic

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
The constraints for the use of PCH are quite strict and a second include
of the same PCH is definitely not supported.

The failure mode isn't very helpful though.