gdb resolves symbolic links for executables in argv[0]

[David Kastrup]

Calling gdb on an executable that is a symbolic link will pass the target of the symbolic link rather than the specified link as argv[0] to the program.

As a result, if the program relies on the contents of argv[0] (for example, for figuring out paths relative to the executable or making decisions based on the name the executable has been called under), debugging fails.

This seems to be a problem newly introduced in Raring.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: gdb 7.6~20130417-0ubuntu1
ProcVersionSignature: Ubuntu 3.8.0-19.29-generic 3.8.8
Uname: Linux 3.8.0-19-generic i686
ApportVersion: 2.9.2-0ubuntu8
Architecture: i386
Date: Sat Apr 27 13:22:35 2013
InstallationDate: Installed on 2011-10-14 (560 days ago)
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release i386 (20111011)
MarkForUpload: True
SourcePackage: gdb
UpgradeStatus: Upgraded to raring on 2013-04-05 (21 days ago)

[David Kastrup (dak)]

Here is an example for a program relying on its argv[0] name: /usr/bin/latex is a symbolic link to /usr/bin/pdftex, and pdftex loads a format depending on the name under which it has been called. As a result,

latex '\stop'

will load the latex.fmt format and finish processing while the same will fail under gdb since argv[0] is being passed as /usr/bin/pdftex instead of /usr/bin/latex:

dak@lola:/tmp$ latex '\stop'
This is pdfTeX, Version 3.1415926-2.4-1.40.13 (TeX Live 2012/Debian)
 restricted \write18 enabled.
entering extended mode
LaTeX2e <2011/06/27>
Babel <v3.8m> and hyphenation patterns for english, dumylang, nohyphenation, bu
lgarian, ukrainian, russian, loaded.
No pages of output.
Transcript written on texput.log.

dak@lola:/tmp$ gdb latex
GNU gdb (GDB) 7.5.91.20130417-cvs-ubuntu
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /usr/bin/pdftex...(no debugging symbols found)...done.
(gdb) run '\stop'
Starting program: /usr/bin/pdftex '\stop'
This is pdfTeX, Version 3.1415926-2.4-1.40.13 (TeX Live 2012/Debian)
 restricted \write18 enabled.
entering extended mode
! Undefined control sequence.
<*> \stop

?

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Joni Salonen (joni-salonen)]

Bug report from upstream shows the issue has just been fixed: http://sourceware.org/bugzilla/show_bug.cgi?id=15415

[Matthias Klose (doko)]

apparently fixed in 14.04 LTS