I know there are lots of ideas, and many ideas without the person from
whom it originates being able or willing to work on it.
This is one of them. So if it will simply vanish, never mind. Anyway
maybe I am lucky, and with this idea I plant a seed, and someday....
I recently run across the following situation (again)
procedure Foo(const s: string;)
begin
// do something
CallBar();
// do more
end;
var GlobalText: String
Foo(GlobalText);
and then in CallBar, "GlobalText" is modified. Which is not allowed.
http://lists.freepascal.org/lists/fpc-devel/2010-July/020966.html
http://lists.freepascal.org/lists/fpc-devel/2010-July/020974.html
The problem of course is that such code is incredible hard to find.
I was thinking it would be cool to have something like range-checks, but for
those strings.
Ideally, the string would be flagged, and other code trying to access it would
check this. But that would mean that all units, packages everything would need
awareness, and had to be compiled with support for the flag.... Not really
practical.
However at least some test would probably work.
If compiled with -Cc (Check Constant string param) or whatever compiler option
it would be, then the code in Foo could have checks.
If foo would copy the value of s (only the address: @s[0], not the string) and
increase the ref-count of s (it still is a pointer to the original s), then Foo
could check on exit.
If anyone modified s, then copy-on-write would have kicked in. either the
address in s, or the ref count would have changed.
That would allow to give at least a warning that something wrong was done.
Martin
_______________________________________________
fpc-devel maillist - fpc-devel@lists.freepascal.org
http://lists.freepascal.org/mailman/listinfo/fpc-devel
