Re: java/1413: gdb loses java type information

[Daniel Jacobowitz <drow at mvista dot com>]

The following reply was made to PR java/1413; it has been noted by GNATS.

From: Daniel Jacobowitz <drow@mvista.com>
To: Tom Tromey <tromey@redhat.com>
Cc: gdb-gnats@sources.redhat.com
Subject: Re: java/1413: gdb loses java type information
Date: Thu, 9 Oct 2003 11:48:13 -0400

 On Thu, Oct 09, 2003 at 09:35:14AM -0600, Tom Tromey wrote:
 > >> You'd need to cast it first.
 > 
 > Daniel> Then I don't think GDB would be right to accept it as-is...
 > 
 > Could you offer more justification for this?  I don't think the java
 > rules are completely relevant here.  After all, java also has member
 > access rules, and gdb ignores those in the interest of providing a
 > good user experience.  I think it makes sense for gdb to follow java
 > syntax in general, but it doesn't have to be slavish about it.
 > 
 > As for other examples... I note that gdb supplies the "@" operator
 > for C/C++, and it also allows you to freely exchange "." and "->" in C.
 > I find the latter compelling as prior art in this case.
 
 It doesn't do the equivalent to what you're asking for, though, which
 would use C++'s RTTI before dereferencing.  At least I'm pretty sure it
 doesn't.
 
 > Daniel> however, a command that printed a value of the run-time type
 > Daniel> would be nice, so that your p $1[0] worked.
 > 
 > This leads to the strange result that "p y[0]" is not valid, but
 > "p y; p $[0]" is.
 > 
 > This change won't render any current valid code invalid.  So you'll
 > still be able to cut and paste java expressions into gdb.  It will
 > just make gdb more useful to people who do a lot of java debugging.
 > 
 > There are other examples of this problem, btw.  It isn't limited to
 > arrays.  For instance, if I have something declared as Object, I can't
 > print any of its fields without casting it to the correct type (which
 > gdb already knows).
 
 I suppose I can see your point.  Maybe "set print object" should
 control this.
 
 -- 
 Daniel Jacobowitz
 MontaVista Software                         Debian GNU/Linux Developer