Re: [PATCH] Fix Tcl quoting in gdb_assert

[Tom Tromey <tromey@adacore.com>]

>>>>> "Simon" == Simon Marchi <simark@simark.ca> writes:

>> -    set code [catch {uplevel 1 expr $condition} res]
>> +    set code [catch {uplevel 1 [list expr $condition]} res]

Simon> I don't understand why this would be needed.  The doc of uplevel says:

Simon>     All of the arg arguments are concatenated as if they had been passed
Simon>     to concat

"concat" is simple string concatenation, but "list" also supplies list
quoting.

Here's a simple example:

    % set text "hello Simon"          
    hello Simon
    % uplevel 0 puts $text
    can not find channel named "hello"
    % uplevel 0 [list puts $text]
    hello Simon

Or more directly:

    % concat puts $text
    puts hello Simon
    % list puts $text
    puts {hello Simon}

Here you can see the result of the [concat] isn't a valid command.

Simon> So, I'm not saying your fix is wrong, I am just saying I don't
Simon> understand the situation.

This part of Tcl has always confused people, you're not alone.  But
basically, for eval-like things you normally want to quote with [list].

I'm not totally sure why it works the way it does, but it might be
because Tcl didn't have a "splat" operator in the early days, so
un-quoting a list to write something like "apply" was more of a pain.

Tom