Re: [pushed 1/4] [gdb/testsuite] Don't use string cat in gdb.dwarf2/dw2-abs-hi-pc.exp

[Tom de Vries <tdevries@suse.de>]

On 4/25/23 20:38, Tom Tromey wrote:
>>>>>> "Tom" == Tom de Vries via Gdb-patches <gdb-patches@sourceware.org> writes:
> 
> Tom> +set sources [lmap i $sources { subst $srcdir/$subdir/$i }]
> 
> Tom> My working set of tcl is a bit random, so I don't know what idiomatic
> Tom> is and what not.
> 
> No worries, Tcl expertise isn't exactly a headline skill.
> 
> Tom> I agree that subst is neater since it needs less quoting.
> 
> It probably has to be { subst { $srcdir/$subdir/$i } }
> since otherwise there will be a second substitution if, say, the srcdir
> has a $ or [] in it.

OK, let's try an example.

We currently have this style:
...
set b d
set l { a $b }
set res [lmap v $l { expr {"$v/c"} }]
foreach v $res {
     puts "V: $v"
}
...
which does:
...
V: a/c
V: $b/c
...

Then with subst we have the same:
...
set res [lmap v $l { subst {$v/c} }]
...
unless we forget the quoting:
...
set res [lmap v $l { subst $v/c }]
...
which gets us instead:
...
V: a/c
V: d/c
...

Hmm, in that case I think subst is the worse choice.  With expr, things 
either parse or not, and if it parses you get the right result.

FWIW, reading a bit more about it I get the impression also set is 
idiomatic, so I came up with this:
...
set res [lmap v $l { set v $v/c ; set v }]
...
which works as well.

Thanks,
- Tom