xerox 19771121 Mesa Language Working Group Minutes free download

File name 19771121_Mesa_Language_Working_Group_Minutes.pdf

XEROX BUSINESS SYSTEMS System Development Division November 21, 1977 To: Distribution From: Dick Sweet Subject: Mesa Language Working Group minutes The Language Working Group met on 15 November, 1977. Monitors were discussed. Recall the items 1. Independent FORK 2. Return type of a FORK 3. Questions of scope 4. Initialization of Monitors and condition variables XEROX SDD ARCHIVES 5. Monitor priority I have read and understood Pages To 6. Condition timeout ----- Rev1ewer _________ Date 7. Aborts # of Pages ---- Ref., 7!&:J;~) 8. Interaction with SIGNALS Item 1. Independent FORK. Provide some system procedure to say "detatch" on the process. It could set the PSB so that joining would either fail or return immediately, or whatever is right. Item 2. Return type of a FORK construct. If pr: PROCEDURE [inrec] RETURNS [outrec] is forked, the value of the FORK construct is a PROCEDURE RETURNS [outrec]; It could be internally be an indirect link into the PSB (with suitable alignment) so that aborting a process would be easier. Items 5 and 6. Monitor Priority and Condition Timeout. If simple (i.e. constant) default parameters are implemented for record declarations, then the priority or timeout can public fields and can be given in the declaration. This would require a change to the compiler to allow constructors for records with private fields. Otherwise, all monitors are created with some default priority and a system procedure is provided to set it otherwise. The same is presumably true for condition timeouts 2 Item 7. Aborts. Not part of the language. Item 8. Interaction with SIGNALS. After considerable discussion, it was decided that one would have to explicitly catch UNWIND in the monitor if it was thought possible that one could happen. The compiler would help by generating an "exit monitor" at the end of an UNWIND catchphrase within an entry procedure. On the subject of detecting the unwinding of a monitor without catching the signal, Butler sug