MS every now and then I trip on some things in the core that I'd like to change and can't. This page is meant to keep a list, additions welcome.
The first batch concerns command invocation:
get rid of TCL_ALLOW_EXCEPTIONS: the library shouldn't care about that and always return the actual code; tclsh's main can do whatever it needs, of course. This functionality seems to have fallen on the wrong side of the border.
of course .... iPtr->result should die!
stop promising that a command receives an empty unshared result in the interpreter: a command has to set its result from scratch, reset it or leave it untouched. This has performance implications, but also enables simpler shell-style pipelining (without nesting [...]). Maybe reserve a variable or have a command to get the interp's result.
Tcl_[GS]etCommandInfo and direct calling of commands!! At least rethink thoroughly
Other things
hide more implementation details behind opaque pointers: interp, CallFrame (don't let anybody else alloc them, they do not need to know the size nor how the core allocates or frees them), ...
change Rule [1] in Tcl.n: let the command be identified after substituting the first word but before substituting the rest. This allows completely bugfree compilation
should return 6 rather than 23 as it currently does?
Precisely! Maybe a better illustration: look at this currently unsolvable (at reasonable cost) bug:
mig@oli:~$ tclsh
% set x 1[proc set args {puts AHA!}]
1
mig@oli:~$ tclsh
% eval {set x 1[proc set args {puts AHA!}]}
AHA!
(Note that that's 8.5, 8.6 may require a different example to show the effect)
change Rule [1] in Tcl.n: let the first word be not a command but a command prefix (aka known as autoexpand first word). Note that this makes it difficult to deal with commands with names that are not proper lists (eg foo{bar}) or that have spaces: they have to be [list]-protected