Re: [OB PATCH] Fix NULL pointer dereference

[Gary Benson <gbenson at redhat dot com>]

Pedro Alves wrote:
> So we reach this call of the 'expansion_notify' function pointer:
> 
>       if (recursively_search_psymtabs (ps, objfile, kind, symbol_matcher, data))
> 	{
> 	  struct compunit_symtab *symtab =
> 	    psymtab_to_symtab (objfile, ps);
> 
> 	  if (expansion_notify != NULL)
> 	    expansion_notify (symtab, data);
> 	}
>     }
> 
> So why can recursively_search_psymtabs find a matching partial
> symbol and thus return true, and then psymtab_to_symtab returns
> NULL, indicating the symtab is empty?  That sounds like a bug?

So the first time psymtab_to_symtab returns NULL, ps->filename is
"src/basic/string-util.h"; the only string-util.h on my system is
/usr/src/debug/systemd-231/src/basic/string-util.h from
systemd-debuginfo-231-10.fc25.x86_64 so I'm assuming it's that.

But, recursively_search_psymtabs is returning 1 not for that psymtab
but for one of its dependencies (the first, as it happens).  That has
no filename, and its user->filename is "<artificial>".  So
recursively_search_psymtabs is saying string-util.h matches because
it matches because of some (shared?) symbol table it references, but
psymtab_to_symtab is being called on the string-util.h psymtab which
doesn't match (or exist?!)

I have no idea what I'm looking at here :(

Thanks,
Gary

-- 
http://gbenson.net/