[Bug pch/46110] New: Precompiled headers: GCC fails to properly locate include files

[Bug pch/46110] New: Precompiled headers: GCC fails to properly locate include files

[aleksey.covacevice at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46110

           Summary: Precompiled headers: GCC fails to properly locate
                    include files
           Product: gcc
           Version: 4.4.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: pch
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: aleksey.covacevice@gmail.com


Created attachment 22102
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22102
Test case script

GCC fails to properly locate include files when using precompiled headers that
are located in a deeper directory in the search path. This problem happens when
a file "z.h" includes two other files, "x.h" and "y.h", such that "y.h" also
includes "x.h", and they are all located in another directory in the include
path (yielding include lines such as '#include "dir/x.h"').

The issue is much better explained through a test case. The following command
sequence is a simple test case that yields the symptom:

==
#!/bin/sh

mkdir -p include/dir pch/dir
touch include/dir/x.h
echo "#include \"dir/x.h\"" > include/dir/y.h
echo "#include \"dir/x.h\"" > include/dir/z.h
echo "#include \"dir/y.h\"" >> include/dir/z.h
gcc -I pch -I include include/dir/x.h -o pch/dir/x.h.gch
gcc -I pch -I include include/dir/y.h -o pch/dir/y.h.gch
gcc -I pch -I include include/dir/z.h -o pch/dir/z.h.gch
==

The output is the following:

==
In file included from include/dir/z.h:2:
include/dir/y.h:1:19: error: pch/dir/x.h: No such file or directory
==

If the include path "-I pch" is ommited from the above commands (i.e., removing
the precompiled headers from the search path), everything runs fine. Also, if
the subdirectory "dir/" is properly removed from every place above, everything
runs fine. Now, if the include path "-I include" is ommited, the output is:

==
include/dir/z.h:2:19: error: dir/y.h: No such file or directory
==

although the precompiled header "pch/dir/y.h.gch" already exists (there should
be no reason to avoid using it, "-Winvalid-pch" does not report anything and
the compilation for "y.h", which is pretty similar, proceeds fine).

The snippet above should also help generate proper ".i" files for further
investigation.

Running GCC on a Ubuntu 9.10 x86 host.

Output of gcc -v:
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.4.1-4ubuntu9'
--with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared
--enable-multiarch --enable-linker-build-id --with-system-zlib
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.4 --program-suffix=-4.4 --enable-nls
--enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc
--enable-targets=all --disable-werror --with-arch-32=i486 --with-tune=generic
--enable-checking=release --build=i486-linux-gnu --host=i486-linux-gnu
--target=i486-linux-gnu
Thread model: posix
gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu9)

Cheers,
Alek

[Bug preprocessor/46110] Precompiled headers: GCC fails to properly locate include files

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46110

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2010.10.21 09:15:29
                 CC|                            |tromey at gcc dot gnu.org
          Component|pch                         |preprocessor
     Ever Confirmed|0                           |1

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-10-21 09:15:29 UTC ---
Including a precompiled header not as the very first preprocessor statement
in a file is not supported.

The issue seems to be that the preprocessor sticks with the first directory
it found the pch in (but obviously doesn't use it) and the original header
file isn't there.

[Bug preprocessor/46110] Precompiled headers: GCC fails to properly locate include files

[aleksey.covacevice at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46110

--- Comment #2 from Aleksey Covacevice <aleksey.covacevice at gmail dot com> 2010-10-21 21:31:14 UTC ---
Richard, thanks for the reply.

Actually the documentation states that other preprocessor directives (such as
"#define"s) can appear before the include line that would include the PCH.
Nevertheless, that is not really the case. In fact it also states that only a
single precompiled header can be used in a particular compilation, and I think
the symptom must be somewhat related to this.

I believe this must be a bug, because even if GCC couldn't use a PCH for any
reason previously stated, it should ignore it and use the original include
file, which in this scenario it can be properly found in the search path.

Thanks again,
Alek