Re: [PATCH] keep-variable command

[Andrew STUBBS <andrew dot stubbs at st dot com>]

Eli Zaretskii wrote:
> It's possible this is something I never knew about: is it actually
> correct that _all_ convenience variables are deleted when `file' is
> used?  The explanation above about their types being lost doesn't make
> sense to me; can you explain?  For example, if I define a variable
> that holds an integer number, why would its type become meaningless?

Currently _all_ convenience variables are deleted when the symbol-file 
command is used. The file command also uses symbol-file.

The explanation I gave refers to the situation after my patch has been 
applied and the debugger is attempting to keep some variables. You are 
correct when you say that basic types will always exist. However, I did 
not want to assume that they will be kept in the same place. Our initial 
implementation did not attempt to fix this up at all and worked for 
quite a while before anybody noticed it didn't work (badly) with unusual 
types. Investigation showed that it was only working with basic types by 
chance - the new types just happened to be at the same addresses, so I 
fixed it up properly as you see it now. There is always the possibility 
of a file redefining any type, of course, so you may not be using the 
int you thought you were using.

> Does this description assume that convenience variables point, or are
> somehow related, to the symbol table?  If so, why does this assumption
> hold for every convenience variable?  I can think of a convenience
> variable that has no relation whatsoever to the symbol table; how does
> such a variable fit into the above scheme?

All variables must have a type, even void ones, as far as I can tell. 
The type is recorded in terms of a reference into a table of types which 
is related to the symbol table in some way I do not claim to fully 
understand. What is certain is that symbol-file wipes the type table.

Please give your example of a convenience variable with no relation to 
the symbol table.

Andrew