Re: [tclquadcode] directSet, directGet, etc. quadcodes

[Donal K. F. <don...@ma...>]

On 03/01/2019 20:23, Kevin Kenny wrote:
> (a) Read traces (if we support them at all) will fire at least once
> for any quadcode sequence that reads a value from a namespace
> variable. Subsequent reads of a value that is known not to have been
> modified since the previous read need not be traced.

The major issue with read traces is linked variables (as created with 
Tcl_LinkVar) since not all user code is good about notifying us when it 
has updated the underlying C variable. Sometimes that's for good reason 
(such as it being a state variable of a non-Tcl system) but the upshot 
is the same: for variables with a read trace, it isn't safe to assume 
anything about their value other than by reading it.

Donal.