Code variables have been able to take a workspace parameter since Select 1. However, an 'unset' of a code variable would be ignored unless the unset was explicitly requesting that the code variable be deleted.
With Select 4 an 'unset' of a code variable will set the variable's value to a null string (0 length). This is unlikely to cause issues with most applications and should help variables which have been changed from being normal variables to code variables. However, it does now mean that the unset operation can now return errors due to the null string not being valid. A typical example of a variable that cannot have a null string would be the Inet$Hostname variable.
As a side effect of this, the *Unset command will now return errors if the error is not 'no such variable'. This ensures that errors during the unset are now visible.
For reference, the workspace parameter to code variables is supplied in R5 on creating the code variable with OS_SetVarVal, and will be passed to the code variable in R12.
SWI OS_SetVarVal (&24)
R0 = pointer to variable name, possibly wildcarded R1 = pointer to new value R2 = length of value, or -1 to delete R3 = pointer to last name, or 0 for first call R4 = variable type to use : 0 = string 1 = number 2 = macro 3 = expanded 4 = literal string 5 = reserved 16 = code variable R5 = workspace to pass to code in R12 (only if R4 = 16)
R3 = new pointer to name R4 = variable type created if evaluated expression
This SWI is used to set a system variable to a value. See PRM 1-311 for more details. The extension from the documented API is the use of a workspace pointer in R5 for code variables. Attempting to delete a code variable will now have the same effect as setting the value to a null string unless the variable type to use is set to 16
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