Re: [PATCH] Mark object files with "target:" filenames as OBJF_NONLOCAL_FILENAME

[Doug Evans <dje at google dot com>]

On Mon, Apr 13, 2015 at 12:07 PM, Gary Benson <gbenson@redhat.com> wrote:
> Hi all,
>
> This patch introduces a new objfile flag OBJF_NONLOCAL_FILENAME to
> denote that objfile->original_name and objfile->obfd->filename are
> filenames referring to files on filesystems other than GDB's local
> filesystem.  allocate_objfile is updated to force
> OBJF_NONLOCAL_FILENAME if the specified name starts with "target:",
> and to not attempt to expand the name using gdb_abspath if flags has
> OBJF_NONLOCAL_FILENAME set.  load_auto_scripts_for_objfile is updated
> to not attempt loading of auto-load scripts for objfiles with
> OBJF_NONLOCAL_FILENAME set in their flags.
>
> A new flag was created rather than reusing OBJF_NOT_FILENAME because
> setting that flag would stop Python's gdb.lookup_objfile from seeing
> the file, and it's not clear that that's desirable.
>
> Without this patch you *sometimes* get things like:
>
>   Reading symbols from /home/gary/target:/lib64/libreadline.so.6...
>
> I haven't figured out why this doesn't always happen but it's plainly
> wrong :)
>
> Built and regtested on RHEL6.6 x86_64.
>
> Ok to commit?
>
> Cheers,
> Gary
>
> gdb/ChangeLog:
>
>         * objfiles.h (OBJF_NONLOCAL_FILENAME): New define.
>         * objfiles.c (allocate_objfile): Force OBJF_NONLOCAL_FILENAME
>         for BFDs with "target:" filenames.  Do not attempt to expand
>         name if flags has OBJF_NONLOCAL_FILENAME set.
>         * auto-load.c (load_auto_scripts_for_objfile): Do not attempt
>         to auto-load scripts for OBJF_NONLOCAL_FILENAME objfiles.

My first thought is that we'll be recording something twice, and that
can lead to problems (e.g., effort has to be expended to keep them in
sync).
"is nonlocal" is already specified by the "target:" in the name.

While I'm all for building on "foo:bar" in path names
(target:foo, remote:foo, and so on), IWBN to build a library on top of that
rather than have sideband tables that recorded such extra info.
[Down the road I can imagine having a class for such things such that
we could augment what's recorded beyond just a "foo:bar" string, but
that's later, if ever.]

IOW, how about having an "is non-local" predicate that is invoked on
the path whenever needed?
[it could be the current "is_target_filename" or if you wanted to add
a layer of abstraction that might be ok, depending on how this might
evolve]

I realize this is a bit incongruous with OBJF_NOT_FILENAME, but I'd
rather head in the above direction than adding more OBJF_ flags.

Thoughts?