Re: gdb follows symlinks when looking for debuginfo

[Olaf Hering <olh@suse.de>]

On Wed, Jan 23, Daniel Jacobowitz wrote:

> On Wed, Jan 23, 2008 at 05:15:37PM +0100, Olaf Hering wrote:
> > 
> > Why does gdb follow symlinks when looking for debuginfo and executables?
> 
> Most likely something uses realpath when opening files.  Looks like
> exec_file_attach -> openp -> xfullpath.
> 
> > The binaries in our installation images are symlinked into a
> > loop-mounted cramfs image, or to an extracted tree on a remote
> > filesystem.
> > The gdb binary itself is a symlink /usr/bin/gdb ->
> > /mounts/inst-sys/usr/bin/gdb. For some reason, gdb starts to look for
> > debuginfo in /mounts/inst-sys/usr/lib/debug instead of just
> > /usr/lib/debug. The same is true for the executable thats being
> > debugged.
> 
> That path is surprising.  I would have expected
> /usr/lib/debug/mounts/inst-sys/...  Does "show sysroot"
> show anything?  What about "show debug-file-directory"?

The current system root is "".
The directory where separate debug symbols are searched for is "/mounts/instsys/usr/lib/debug".

You are right. I should have pasted the correct path into the mail.

For 3 yast libs (the first 3 libs to load), the path is wrong.

inst-sys:/ # grep y2wfm.so /X
2953  open("/usr/lib/YaST2/plugin/libpy2wfm.so.2", O_RDONLY) = 7
2953  stat64("/usr/lib/YaST2/plugin/libpy2wfm.so.2", {st_mode=S_IFREG|0755, st_size=121048, ...}) = 0
2953  open("/usr/lib/YaST2/plugin/libpy2wfm.so.2", O_RDONLY) = 7
2953  open("/mounts/instsys/usr/lib/YaST2/plugin/libpy2wfm.so.2.0.0.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
2953  open("/mounts/instsys/usr/lib/YaST2/plugin/.debug/libpy2wfm.so.2.0.0.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
2953  open("/mounts/instsys/usr/lib/debug//mounts/instsys/usr/lib/YaST2/plugin/libpy2wfm.so.2.0.0.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
2953  open("/mounts/instsys/usr/lib/debug/mounts/instsys/usr/lib/YaST2/plugin/libpy2wfm.so.2.0.0.debug", O_RDONLY) = -1 ENOENT (No such file or directory)

Should have been /mounts/instsys/usr/lib/debug/usr/lib/YaST2/plugin/libpy2wfm.so.2.0.0.debug
Maybe wrong debuginfo generated by gcc? They are not dlopen objects.

For all others the debuginfo can be loaded.
inst-sys:/ # grep libexpat.so.1 /X
2953  open("/lib/libexpat.so.1", O_RDONLY) = 3
2953  open("/lib/libexpat.so.1", O_RDONLY) = 13
2953  stat64("/lib/libexpat.so.1", {st_mode=S_IFREG|0755, st_size=193996, ...}) = 0
2953  open("/lib/libexpat.so.1", O_RDONLY) = 5
2953  open("/lib/libexpat.so.1.5.2.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
2953  open("/lib/.debug/libexpat.so.1.5.2.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
2953  open("/mounts/instsys/usr/lib/debug//lib/libexpat.so.1.5.2.debug", O_RDONLY) = 6
2953  stat64("/mounts/instsys/usr/lib/debug//lib/libexpat.so.1.5.2.debug", {st_mode=S_IFREG|0644, st_size=289219, ...}) = 0
2953  open("/mounts/instsys/usr/lib/debug//lib/libexpat.so.1.5.2.debug", O_RDONLY) = 6

The gdb output is:
...............
Reading symbols from /mounts/instsys/usr/lib/YaST2/plugin/libpy2wfm.so.2...expanding to full symbols...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/YaST2/plugin/libpy2wfm.so.2
Reading symbols from /mounts/instsys/usr/lib/YaST2/plugin/libpy2scr.so.2...expanding to full symbols...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/YaST2/plugin/libpy2scr.so.2
Reading symbols from /mounts/instsys/usr/lib/YaST2/plugin/libpy2UI.so.2...expanding to full symbols...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/YaST2/plugin/libpy2UI.so.2
Reading symbols from /usr/lib/libscr.so.2...expanding to full symbols...Reading symbols from /mounts/instsys/usr/lib/debug/usr/lib/libscr.so.2.0.0.debug...expanding to full symbols...done.
done.
..............

Why are the first 3 libs searched in  /mounts/instsys instead of /?