Re: QUERY: Pretty-printing C++ classes in gdb

[Daniel Jacobowitz <drow at mvista dot com>]

On Fri, Mar 08, 2002 at 04:56:43PM -0800, Bradford Chamberlain wrote:
> 
> (I hope the following is not a FAQ.  I didn't find one on the gdb page.)
> 
> I am curious whether gdb has hooks that would allow me to provide a means
> of pretty-printing C++ classes without modifying the gdb source code.  
> For example, imagine that I am supplying you with a C++ class library, and
> want to save you the hassle of inspecting the guts of my classes and
> understanding their inner workings when debugging your code that uses
> them.  Rather, I'd like to cause "p instanceOfClassFoo" to give you a
> clean view of the class that doesn't require understanding its
> implementation.
> 
> One way to do this would be to hack the source, perhaps treating my
> library as a new language.  However, I'd like to avoid changing the gdb
> source both for simplicity and so that I don't have to ship users a new
> copy of gdb.  So is there a less intrusive way that I can hook my pretty
> printing in?  For example, I could imagine that a well-defined method name
> or operator<< overload might be utilized by gdb if it exists.  Or that
> perhaps I can give you a dot-file that will be used at load time to
> configure the behavior.
> 
> Any information on whether such a feature exists, or other possible
> workarounds would be appreciated.

The standard way to do this is:

  - Provide a .gdbinit.  Placed in the current working directory or in
$HOME, it lets you specify commands to be executed.

  - Provide utility functions or methods to print each class however
you wish.

  - Provide aliases in the former to call the latter.

GDB will probably never do this by default for some method name or
operator overload; it is not appropriate (what if the functions affect
state?).  Be sure to write the print functions carefully.


-- 
Daniel Jacobowitz                           Carnegie Mellon University
MontaVista Software                         Debian GNU/Linux Developer