DIRECTORYBasics USING [BYTE],MesaRuntimeInit USING [],PrincOps USING [BytePC, ControlLink, --FieldDescriptor, --Frame, FrameHandle, localbase, markOffset, NullFrame, NullLink, SD, sError, sErrorList, sReturnError, sReturnErrorList, sSignal, sSignalList, StateVector, sUnnamedError, zCATCH, zJ2, zJ9, zJB, zJW, zLADRB, zPORTI, zWF],PrincOpsUtils USING [Alloc, Codebase, Free, GetReturnFrame, GetReturnLink, MyGlobalFrame, MyLocalFrame, SetReturnLink],RuntimeError USING [UCSProc];SignalsImpl: MONITORIMPORTS PrincOpsUtilsEXPORTS MesaRuntimeInit, RuntimeError =BEGINBYTE: TYPE = Basics.BYTE;CatchPointer: TYPE = POINTER TO catch PrincOps.Frame;CatchCall: TYPE = PROCEDURE [SIGNAL ANY RETURNS ANY] RETURNS [ActionCode];CatchContinue: TYPE = PROCEDURE;ActionCode: TYPE = INTEGER;reject: ActionCode = 0;resume: ActionCode = 1;exit: ActionCode = -1;ucsHandler: RuntimeError.UCSProc _ NIL;SendMsgSignal: PUBLIC SIGNAL RETURNS [UNSPECIFIED, UNSPECIFIED] = CODE;ResumeError: PUBLIC SIGNAL = CODE;UNCAUGHT: PUBLIC ERROR [signal: SIGNAL ANY RETURNS ANY, parameters: UNSPECIFIED] = CODE;InformationalSignal: PUBLIC SAFE PROC [signal: SIGNAL] = TRUSTED {MarkSignalHandlerFrame[FALSE];SignalHandler[signal, -1, TRUE];};RegisterUncaughtSignalHandler: PUBLIC ENTRY PROC [proc: RuntimeError.UCSProc]RETURNS [old: RuntimeError.UCSProc] = {old _ ucsHandler; ucsHandler _ proc};Error: PROC [signal: SIGNAL ANY RETURNS ANY, message: UNSPECIFIED] = {MarkSignalHandlerFrame[FALSE];SignalHandler[signal, message];ERROR ResumeError};ErrorList: PROC [signal: SIGNAL ANY RETURNS ANY, message: POINTER TO UNSPECIFIED] = {MarkSignalHandlerFrame[FALSE];SignalHandler[signal, message !UNWIND => PrincOpsUtils.Free[message]];PrincOpsUtils.Free[message];  ERROR ResumeError};ReturnError: PROC [signal: SIGNAL ANY RETURNS ANY, message: UNSPECIFIED] = {caller: PrincOps.FrameHandle = PrincOpsUtils.GetReturnFrame[];PrincOpsUtils.SetReturnLink[caller.returnlink];MarkSignalHandlerFrame[FALSE];SignalHandler[signal, message ! UNWIND => PrincOpsUtils.Free[caller]];PrincOpsUtils.Free[caller];  ERROR ResumeError};ReturnErrorList: PROC [signal: SIGNAL ANY RETURNS ANY, message: POINTER TO UNSPECIFIED] = {caller: PrincOps.FrameHandle = PrincOpsUtils.GetReturnFrame[];PrincOpsUtils.SetReturnLink[caller.returnlink];MarkSignalHandlerFrame[FALSE];SignalHandler[signal, message! UNWIND => {PrincOpsUtils.Free[caller]; PrincOpsUtils.Free[message]}];PrincOpsUtils.Free[caller];  PrincOpsUtils.Free[message];  ERROR ResumeError};UnnamedError: PROC = {MarkSignalHandlerFrame[FALSE];SignalHandler[LOOPHOLE[-1], -1];ERROR ResumeError};Signal: PROC [signal: SIGNAL ANY RETURNS ANY, message: UNSPECIFIED] = {MarkSignalHandlerFrame[FALSE];SignalHandler[signal, message];};SignalList: PROC [signal: SIGNAL ANY RETURNS ANY, message: POINTER TO UNSPECIFIED] = {MarkSignalHandlerFrame[FALSE];SignalHandler[signal, message ! UNWIND => PrincOpsUtils.Free[message]];PrincOpsUtils.Free[message];};MarkSignalHandlerFrame: PROC [value: BOOL] = MACHINE CODE {PrincOps.zLADRB, 0;PrincOps.zWF,--PrincOps.FieldDescriptor[offset: PrincOps.markOffset, posn: 0, size: 1]--PrincOps.markOffset, 0;};SignalHandler: PROC [signal: SIGNAL ANY RETURNS ANY, message: UNSPECIFIED, informational: BOOL _ FALSE] = {SignalFrame: TYPE = POINTER TO FRAME[SignalHandler];frame, nextFrame: PrincOps.FrameHandle;target, nextTarget: PrincOps.FrameHandle;self: PrincOps.FrameHandle = PrincOpsUtils.MyLocalFrame[];start: PrincOps.FrameHandle;catchFrame: CatchPointer;action: ActionCode;unwinding: BOOL;catchPhrase: BOOL;catchFSIndex: BYTE;catchPC, exitPC: PrincOps.BytePC;catchState: PrincOps.StateVector;MarkSignalHandlerFrame[TRUE];  unwinding _ FALSE;start _ GetFrame[self.returnlink];  target _ PrincOps.NullFrame;  DOnextFrame _ start;UNTIL nextFrame = target DOframe _ nextFrame;IF frame.accesslink = PrincOpsUtils.MyGlobalFrame[] AND frame.mark THEN {OPEN thisSignaller: LOOPHOLE[frame, SignalFrame];IF unwinding THEN {IF signal = thisSignaller.signal THENnextTarget _ IF thisSignaller.unwindingTHEN thisSignaller.nextTargetELSE thisSignaller.nextFrame;IF thisSignaller.unwinding THEN {IF thisSignaller.frame = LOOPHOLE[frame.returnlink] THENframe.returnlink _ [frame[thisSignaller.nextFrame]];PrincOpsUtils.Free[thisSignaller.frame];};nextFrame _ GetFrame[frame.returnlink];}ELSEnextFrame _ IF signal ~= thisSignaller.signal THENIF thisSignaller.unwindingTHEN thisSignaller.nextFrameELSE GetFrame[frame.returnlink]ELSEIF thisSignaller.unwindingTHEN thisSignaller.nextTargetELSE thisSignaller.nextFrame;}ELSE nextFrame _ GetFrame[frame.returnlink];IF unwinding AND nextTarget = frame THEN  nextTarget _ nextFrame;[catchPhrase, catchFSIndex, catchPC] _ CheckCatch[frame];IF catchPhrase THEN {catchFrame _ PrincOpsUtils.Alloc[catchFSIndex];catchFrame^ _ PrincOps.Frame[accesslink: frame.accesslink,pc: catchPC,returnlink: [frame[self]],extensions: catch[unused: ,staticlink: frame+PrincOps.localbase, messageval: message]];action _ LOOPHOLE[catchFrame, CatchCall][IF unwinding THEN LOOPHOLE[UNWIND] ELSE signal! SendMsgSignal => RESUME[message, signal]];catchState _ STATE;SELECT action FROMreject =>  NULL;resume =>IF unwindingTHEN ERROR ResumeErrorELSE {catchState.dest _ PrincOpsUtils.GetReturnLink[];catchState.source _ PrincOps.NullLink;RETURN WITH catchState};exit =>IF ~informational THEN {exitPC _ catchFrame.pc;PrincOpsUtils.Free[catchFrame];target _ LOOPHOLE[catchState.stk[0]-PrincOps.localbase];nextTarget _ nextFrame;unwinding _ TRUE;  message _ NIL;GO TO StartUnwind;};ENDCASE;};IF unwinding THEN {IF frame = start THEN start _ nextFrame;IF frame = LOOPHOLE[self.returnlink] THEN self.returnlink _ [frame[nextFrame]];PrincOpsUtils.Free[frame];};REPEATStartUnwind => NULL;FINISHED => EXITENDLOOP;ENDLOOP;SELECT TRUE FROMunwinding => target.pc _ exitPC;informational OR signal = LOOPHOLE[UNCAUGHT] => NULL;  -- does an implicit RESUMEENDCASE => {Uncaught: TYPE = SIGNAL [SIGNAL ANY RETURNS ANY, UNSPECIFIED];LOOPHOLE[UNCAUGHT, Uncaught][signal, message];ucsHandler[message, signal, frame];};};CheckCatch: PROC [frame: PrincOps.FrameHandle]RETURNS [catchPhrase: BOOL, fsIndex: BYTE, pc: PrincOps.BytePC] = {code: LONG POINTER TO PACKED ARRAY [0..0) OF BYTE;MarkSignalHandlerFrame[FALSE];code _ PrincOpsUtils.Codebase[frame.accesslink];pc _ [frame.pc];DOSELECT code[pc] FROMPrincOps.zCATCH => {catchPhrase _ TRUE; EXIT};PrincOps.zPORTI => pc _ [pc + 1];ENDCASE => {catchPhrase _ FALSE; EXIT};ENDLOOP;IF catchPhrase THEN {fsIndex _ code[pc+1];SELECT code[pc _ [pc+2]] FROMPrincOps.zJB => pc _ [pc + 2];IN [PrincOps.zJ2..PrincOps.zJ9] => pc _ [pc + 1];PrincOps.zJW => pc _ [pc + 3];ENDCASE;};};GetFrame: PROC [link: PrincOps.ControlLink] RETURNS [PrincOps.FrameHandle] =  {DOIF ~link.proc THENIF link.indirect THEN link _ link.link^ELSE --frame link-- RETURN[link.frame]ELSE RETURN[PrincOps.NullFrame];ENDLOOP;};Initialize: PROCEDURE = {pSD: POINTER TO ARRAY [0..0) OF UNSPECIFIED _ PrincOps.SD;pSD[PrincOps.sSignalList] _ SignalList;pSD[PrincOps.sSignal] _ Signal;pSD[PrincOps.sErrorList] _ ErrorList;pSD[PrincOps.sError] _ Error;pSD[PrincOps.sReturnErrorList] _ ReturnErrorList;pSD[PrincOps.sReturnError] _ ReturnError;pSD[PrincOps.sUnnamedError] _ UnnamedError;};Initialize[];END.   ю  SignalsImpl.mesalast edited by Levin on September 20, 1983 11:14 amTypes and Related DeclarationsGlobal Variables (protected by monitor)Exported to RuntimeErrorLanguage support routinesInternal ProcedurescatchFrame is waiting to execute its exit jumpWe want to be able to RESUME UNCAUGHT, but we don't want a random catch phrase to do so.  So, we declare it to be an ERROR in the interface, but raise it as a SIGNAL here.  When (if) UNCAUGHT percolates to the top of the stack, it is implicitly resumed (see the preceding line of code).  Control then passes to the statement following the invocation of UNCAUGHT, which calls the debugger (or whatever).code[pc] points at zCatchMarkSignalHandlerFrame[FALSE];Initialization Э╩
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