Re: convenience variables in "target remote"

[Vladimir Prus <ghost@cs.msu.su>]

On Thursday 10 November 2005 16:43, Daniel Jacobowitz wrote:
> On Thu, Nov 10, 2005 at 01:29:46PM +0300, Vladimir Prus wrote:
> > Hi,
> > it looks like "target remote" command does not handle convenience
> > variables properly:
> >
> >    (gdb) set $var=1234
> >    (gdb) target remote :$var
> >
> >    :$var: Connection refused.
> >
> >    (gdb) target remote :1234
> >    Remote debugging using :1234
> >
> > When $var is used, it's not expanded, at gdb tries to connect to the
> > wrong port?
> >
> > Is this by design, or a bug?
>
> Convenience variables are expanded in roughly the same places that the
> (C) expression evaluator is used to parse expressions.  

That's pretty vague, I think. Does documentation say where exactly that "(C)" 
expression evaluator is used? If not, then guesswork is the only way to find 
out.

> Most places 
> that take a number do not support them; that's by design, the full
> range of expressions are not supported for ports.

In fact, it seems like only literals are supported for ports. This, just like 
requirements that "x" command accept only literal as the number of bugs, 
seems like arbitrary restriction for me.

Specifically, in KDevelop for remote debugging, user should provide a shell 
script to run program remotely, and a gdb script to connect to a program.
The gdb script can just containg "target remote somehost:1234". But I don't 
think it's unreasonable for two people to remotely debug program on the same 
box. So, port should not be hardcoded.

I though about using convenience variables to pass port number from "run 
program" script to "connect to target" gdb script, but due to above 
limitation, this is not possible. So, I should have shell script that will be 
given port number and will produce the set of gdb commands to connect to the 
target. Another level of scripting just to overcome arbitrary restriction in 
gdb.
Or is there some indirect way to use variable in "target remote" command?

- Volodya