Obscure feature requests

[erkyrath]

This is various pieces of information which the compiler could provide which we don't have a real use case for, but the idea came up and I want to write it down. Very low priority.

[erkyrath]

Current routine address

Maybe a system constant #current_routine. This returns routine_start_pc with marker IROUTINE_MV. (Divide by scale_factor in Z-code.) If used outside a routine definition, it's an error.

[erkyrath]

Number of local variables

Similarly, #local_variable_count could return routine_locals. Error outside a function definition.

[erkyrath]

Absolute address of a label

You can @jumpabs to a label given its address, but there's currently no way to get this. (Would only be possible in Glulx, as Z-code label addresses don't generally fit in a 16-bit value, and there is no @jumpabs in Z-code anyway.)

Label addresses aren't handled in backpatching; they're figured out by special code in transfer_routine(). So this is messy, and it would be messier if you want to retain the addresses of labels outside the code of the routine itself.

Might want a special syntax for this, maybe ..LabelName; -- defines the label as a global symbol and also adds it to a list of labels to remember through compilation.

(Backpatching this requires care, too. I think we'd need a new marker which indexes into a table of (routine address, offset).)

[erkyrath]

Local variable index

The offset where a local occurs in the locals segment. Like #g$GLOBAL, but for locals. The obvious spelling would be #l$LOCAL.

This value would be pretty hard to use. There's no way to access the locals segment except with an opcode argument, and those have fixed offsets. I guess self-modifying code could generate an opcode to do this.

[curiousdannii]

This value would be pretty hard to use. There's no way to access the locals segment except with an opcode argument, and those have fixed offsets.

Yeah I've realised that... that might end up being the trickiest part of all this. Or maybe just the most verbose - I could do it with a long switch statement.