Sound_RemoveVoice can return an error

The PRM for Sounds_RemoveVoice states:

If an error occurs, this SWI does not set V in the usual manner. Instead R1 is zero on exit, and R0 points directly to a null-terminated error string.

And yet the following Repro returns an error

BASIC
SYS "Sound_RemoveVoice"

Illegal voice index

This change in behaviour started with RISC OS 3. To resolve the exit code at line 998 in Sound0 needs changing from:

BL      CopyError
EXIT

to:

BL      CopyError
MOV     r1, #0
CLRV
EXIT

As the PRM is documenting a non standard behaviour, where as the SWI is implementing a standard behaviour, wouldn’t it make more sense to change the documentation?

As the PRM is documenting a non standard behaviour, where as the SWI is implementing a standard behaviour, wouldn’t it make more sense to change the documentation?

I agree, there is no need to reintroduce a RISC OS 2 behaviour at this stage.

Is Sound_InstallVoice similarly no longer RISC OS 2 behaviour? They ought at least to behave the same way…

there is no need to reintroduce a RISC OS 2 behaviour at this stage.

Sound_InstallVoice 1 handles errors in the same way and it was introduced in RO3, so its not strictly RO2 behaviour.

I agree that its odd that this and a few other SWI’s don’t return errors in the usual way. They must have been implemented that way for a reason, although I can’t for the life of me think why.