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Re: set sysroot command on AIX has no effect.
Hi Ulrich,
>
> > Calling solib_find returning a prefixed sysroot path and the
duplication
> > can be avoided as you suggested.
> > But calling solib_bfd_fopen after this is causing the assertion to
fail on
> > NULL path as solib_bfd_fopen doing xfree of pathname at the end.
>
> Well, of course, you have to check for NULL. What I'm suggesting is to
> use something along the lines of:
>
> found_pathname = solib_find (filename, &found_file);
> if (found_pathname == NULL)
> // error handling
> archive_bfd = solib_bfd_fopen (found_pathname, found_file);
>
Yes, i did try these steps. But this won't set the sysroot path as we
intend to.
The final object filename we want is the one returned from solib_find,
which is a sysroot prefixed pathname.
After solib_bfd_fopen call we can't refer to found_pathname as it's been
freed in solib_bfd_fopen at the end, and assertion failure later.
> where the code currently does:
>
> archive_bfd = gdb_bfd_open (filename, gnutarget, -1);
> if (archive_bfd == NULL)
> // error handling
>
>
> > + pathname = solib_find (filename, &found_file);
> > + if (pathname == NULL)
> > + perror_with_name (filename);
> > archive_bfd = gdb_bfd_open (filename, gnutarget, -1);
> > if (archive_bfd == NULL)
> > {
>
> This has a number of problems:
> - you still use gdb_bfd_open with filename, which means it still won't
> find the file (I assume you meant to use pathname?)
pathname we get is something like "/usr/lib/libc.a(shr.o)", Offcourse
their is no such file with this pathname in the system.
So we set a filename as "/usr/lib/libc.a" after separating member name
from actual file and gdb_bfd_open does find the file and return it's bfd.
Here if we pass the path returned from solib_find to gdb_bfd_open instead
of filename then no issue is seen.
filename is a malloc'ed string which will be freed up when do_cleanups is
called before existing from solib_aix_bfd_open.
> - if solib_find actually finds the file, "found_file" is an open file
> descriptor, which the code now leaks
I too was bit reluctant about found_file use after solib_find, but wanted
to have your view.
> - actually, the pathname string now also leaks
> - and finally, at the bottom:
> object_bfd->filename = xstrdup (pathname);
> you now miss the object file name (in parentheses), so
> "info sharedlibrary" will no longer show it
>
> Most of those should be fixed when using the approach above.
pathname string we need to assign to object filename is the one which is
returned from solib_find which gives us sysroot path.
We aren't modifying actual pathname which we got from solib_map_sections,
just reusing the pathname variable locally, so as to assign that to object
filename.
I confirmed this with debugging gdb and pasted the output of gdb session
below.
I think, better we use found_pathname variable to store returned value
from solib_find instead of using existing pathname variable to avoid
confusion.
And may assign object filename as "object_bfd->filename = xstrdup
(found_pathname);" ?
The only problem i think if we use solib_find without using
solib_bfd_fopen is found_file descriptor.
Let me know your view.
output of gdb session before call to solib_aix_bfd_open & after return
from solib_aix_bfd_open
----------------------------------------------------------------------------------------------
Breakpoint 3, _ZL18solib_map_sectionsP7so_list (so=0x1102d8bd0) at
solib.c:547
547 abfd = ops->bfd_open (filename);
(top-gdb) p *so
$7 = {next = 0x1102d9030, lm_info = 0x1102ca310,
so_original_name = "/usr/lib/libc.a(shr.o)", '\000' <repeats 489 times>,
so_name = "/usr/lib/libc.a(shr.o)", '\000' <repeats 489 times>, pspace =
0x11025be70,
abfd = 0x0, symbols_loaded = 0 '�', objfile = 0x0, sections = 0x0,
sections_end = 0x0,
addr_low = 0, addr_high = 0}
(top-gdb) p filename
$8 = 0x110273b70 "/usr/lib/libc.a(shr.o)"
(top-gdb) n
548 do_cleanups (old_chain);
(top-gdb) p *so
$9 = {next = 0x1102d9030, lm_info = 0x1102ca310,
so_original_name = "/usr/lib/libc.a(shr.o)", '\000' <repeats 489 times>,
so_name = "/usr/lib/libc.a(shr.o)", '\000' <repeats 489 times>, pspace =
0x11025be70,
abfd = 0x0, symbols_loaded = 0 '�', objfile = 0x0, sections = 0x0,
sections_end = 0x0,
addr_low = 0, addr_high = 0}
(top-gdb) p filename
$10 = 0x110273b70 "/usr/lib/libc.a(shr.o)"
(top-gdb)
Thanks,
-Sangamesh
From: "Ulrich Weigand" <uweigand@de.ibm.com>
To: Sangamesh Mallayya/India/IBM@IBMIN
Cc: gdb-patches@sourceware.org
Date: 10/08/2016 01:01 AM
Subject: Re: set sysroot command on AIX has no effect.
Sangamesh Mallaya wrote:
> Calling solib_find returning a prefixed sysroot path and the duplication
> can be avoided as you suggested.
> But calling solib_bfd_fopen after this is causing the assertion to fail
on
> NULL path as solib_bfd_fopen doing xfree of pathname at the end.
Well, of course, you have to check for NULL. What I'm suggesting is to
use something along the lines of:
found_pathname = solib_find (filename, &found_file);
if (found_pathname == NULL)
// error handling
archive_bfd = solib_bfd_fopen (found_pathname, found_file);
where the code currently does:
archive_bfd = gdb_bfd_open (filename, gnutarget, -1);
if (archive_bfd == NULL)
// error handling
> + pathname = solib_find (filename, &found_file);
> + if (pathname == NULL)
> + perror_with_name (filename);
> archive_bfd = gdb_bfd_open (filename, gnutarget, -1);
> if (archive_bfd == NULL)
> {
This has a number of problems:
- you still use gdb_bfd_open with filename, which means it still won't
find the file (I assume you meant to use pathname?)
- if solib_find actually finds the file, "found_file" is an open file
descriptor, which the code now leaks
- actually, the pathname string now also leaks
- and finally, at the bottom:
object_bfd->filename = xstrdup (pathname);
you now miss the object file name (in parentheses), so
"info sharedlibrary" will no longer show it
Most of those should be fixed when using the approach above.
Bye,
Ulrich
--
Dr. Ulrich Weigand
GNU/Linux compilers and toolchain
Ulrich.Weigand@de.ibm.com