Re: 2GB limitation

Emiliano <emiliano@example.invalid> wrote:

In 9.0 the type of the 'length' member of the Tcl_Obj struct (the number of
bytes at '*bytes' member, not including the terminating null) has changed
from int to ptrdiff_t, so it will remain (1<<31)-1 => 2147483647 bytes on
32 bit platforms (unsurprisingly) and (1<<63)-1 => 9223372036854775807
(9,22 exabyte) on 64 bit platforms.

My hearsay was "generally 64 bit (minus the sign-bit)".
Are you sure that length-type is *always* ptrdiff_t, and
that this may be 32bit?

The "64bit'ness" of a platform is also a bit more complicated...
There are platforms, where pointers are 64bit, but ints are
still 32 (despite machine words being all 64bit) - in those
cases, I'd expect ptrdiff_t to be 64 bit, but on a real old
32bit machine, I don't really know for sure...

IIUC that's also the (new) number of elements for a Tcl list.
In practice the number will be less, since the length of the
string representation of such list will hit the '*bytes' max
length first.

Not all lists are ever turned to string-rep.  While they are
semantically "just strings", well written programs can avoid
the actual obtainment of the string rep, at least for those
really long lists that may be relevant here.