Fix crash when timeouts and break loops get mixed up.

Ensure that the jump buffer is restored correctly when returning from
a break loop. Imposes maximum depth limit for timeouts of 1024.

src/gap.c

@@ -1363,15 +1363,17 @@ Obj FuncSetUserHasQuit( Obj Self, Obj value)
 }
 
 
- syJmp_buf AlarmJumpBuffer;
+ #define MAX_TIMEOUT_NESTING_DEPTH 1024
+
+ syJmp_buf AlarmJumpBuffers[MAX_TIMEOUT_NESTING_DEPTH];
+ UInt NumAlarmJumpBuffers = 0;
 
  Obj FuncTIMEOUTS_SUPPORTED(Obj self) {
    return SyHaveAlarms ? True: False;
  }
 
  Obj FuncCALL_WITH_TIMEOUT( Obj self, Obj seconds, Obj microseconds, Obj func, Obj args )
 {
-  syJmp_buf alarmJumpBuffer;
   Obj plain_args;
     Obj res;
     Obj currLVars;
@@ -1396,12 +1398,14 @@ Obj FuncSetUserHasQuit( Obj Self, Obj value)
     else 
       plain_args = args;
     if (SyAlarmRunning)
-      ErrorMayQuit("CALL_WITH_TIMEOUT cannot currently be nested. There is already a timeout running", 0, 0);
-    memcpy((void *)&alarmJumpBuffer, (void *)&TLS(AlarmJumpBuffer), sizeof(AlarmJumpBuffer));
+      ErrorMayQuit("CALL_WITH_TIMEOUT cannot currently be nested except via break loops."
+		   " There is already a timeout running", 0, 0);
+    if (NumAlarmJumpBuffers++ >= MAX_TIMEOUT_NESTING_DEPTH)
+      ErrorMayQuit("Nesting depth of timeouts via break loops limited to %i", MAX_TIMEOUT_NESTING_DEPTH, 0L);
     currLVars = TLS(CurrLVars);
     currStat = TLS(CurrStat);
     recursionDepth = TLS(RecursionDepth);
-    if (sySetjmp(TLS(AlarmJumpBuffer))) {
+    if (sySetjmp(AlarmJumpBuffers[NumAlarmJumpBuffers])) {
       /* Timeout happened */
       TLS(CurrLVars) = currLVars;
       TLS(PtrLVars) = PTR_BAG(TLS(CurrLVars));
@@ -1451,10 +1455,45 @@ Obj FuncSetUserHasQuit( Obj Self, Obj value)
         SET_LEN_PLIST(res,0);
       }
     }
-    memcpy((void *)&TLS(AlarmJumpBuffer), (void *)&alarmJumpBuffer, sizeof(syJmp_buf));
+    assert(NumAlarmJumpBuffers);
+    NumAlarmJumpBuffers--;
     return res;
 }
 
+Obj FuncSTOP_TIMEOUT( Obj self ) {
+  UInt seconds, nanoseconds;
+  if (!SyHaveAlarms || !SyAlarmRunning) 
+    return Fail;
+  SyStopAlarm(&seconds, &nanoseconds);
+  Obj state = NEW_PLIST(T_PLIST_CYC+IMMUTABLE, 3);
+  SET_ELM_PLIST(state,1,INTOBJ_INT(seconds));
+  SET_ELM_PLIST(state,2,INTOBJ_INT(nanoseconds/1000));
+  SET_ELM_PLIST(state,3,INTOBJ_INT(NumAlarmJumpBuffers));
+  SET_LEN_PLIST(state,3);
+  return state;
+}
+
+Obj FuncRESUME_TIMEOUT( Obj self, Obj state ) {
+  if (!SyHaveAlarms || SyAlarmRunning) 
+    return Fail;
+  if (!IS_PLIST(state) || LEN_PLIST(state) < 2)
+    return Fail;
+  if (!IS_INTOBJ(ELM_PLIST(state,1)) ||
+      !IS_INTOBJ(ELM_PLIST(state,2)))
+    return Fail;
+  Int s = INT_INTOBJ(ELM_PLIST(state,1));
+  Int us = INT_INTOBJ(ELM_PLIST(state,2));
+  if (s < 0 || us < 0 || us > 999999)
+    return Fail;
+  Int depth = INT_INTOBJ(ELM_PLIST(state,3));
+  if (depth < 0 || depth >= MAX_TIMEOUT_NESTING_DEPTH)
+    return Fail;
+  NumAlarmJumpBuffers = depth;
+  SyInstallAlarm(s, 1000*us);
+  return True;
+}
+
+
 
 /****************************************************************************
 **
@@ -3018,6 +3057,12 @@ static StructGVarFunc GVarFuncs [] = {
     { "CALL_WITH_TIMEOUT", 4, "seconds, microseconds, func, args",
       FuncCALL_WITH_TIMEOUT, "src/gap.c:CALL_WITH_TIMEOUT" },
 
+    {"STOP_TIMEOUT", 0, "",
+     FuncSTOP_TIMEOUT, "src/gap.c:FuncSTOP_TIMEOUT" },
+
+    {"RESUME_TIMEOUT", 1, "state",
+     FuncRESUME_TIMEOUT, "src/gap.c:FuncRESUME_TIMEOUT" },
+
     { "JUMP_TO_CATCH", 1, "payload",
       FuncJUMP_TO_CATCH, "src/gap.c:JUMP_TO_CATCH" },
 

src/gap.h

@@ -49,6 +49,16 @@ extern UInt Last3;
 */
 extern UInt Time;
 
+/****************************************************************************
+**
+*V  AlarmJumpBuffer . . . . . .long jump buffer used for timeouts 
+**
+**  Needs to be visible to code in read.c that stores away execution state 
+*/
+
+
+extern syJmp_buf AlarmJumpBuffers[];
+extern UInt NumAlarmJumpBuffers;
 
 
 /****************************************************************************

src/stats.c

@@ -1684,7 +1684,7 @@ UInt ExecIntrStat (
        CallWithTimeLimit where we started */
 
     if ( SyAlarmHasGoneOff ) 
-      syLongjmp(AlarmJumpBuffer,1);
+      syLongjmp(AlarmJumpBuffers[NumAlarmJumpBuffers],1);
 
     /* and now for something completely different                          */
     SET_BRK_CURR_STAT( stat );

src/sysfiles.c

@@ -1569,34 +1569,6 @@ void SyStopAlarm(UInt *seconds, UInt *nanoseconds) {
 #endif
 #endif
 
-Obj FuncSTOP_TIMEOUT( Obj self ) {
-  UInt seconds, nanoseconds;
-  if (!SyHaveAlarms || !SyAlarmRunning) 
-    return Fail;
-  SyStopAlarm(&seconds, &nanoseconds);
-  Obj state = NEW_PLIST(T_PLIST_CYC+IMMUTABLE, 2);
-  SET_ELM_PLIST(state,1,INTOBJ_INT(seconds));
-  SET_ELM_PLIST(state,2,INTOBJ_INT(nanoseconds/1000));
-  SET_LEN_PLIST(state,2);
-  return state;
-}
-
-Obj FuncRESUME_TIMEOUT( Obj self, Obj state ) {
-  if (!SyHaveAlarms || SyAlarmRunning) 
-    return Fail;
-  if (!IS_PLIST(state) || LEN_PLIST(state) < 2)
-    return Fail;
-  if (!IS_INTOBJ(ELM_PLIST(state,1)) ||
-      !IS_INTOBJ(ELM_PLIST(state,2)))
-    return Fail;
-  Int s = INT_INTOBJ(ELM_PLIST(state,1));
-  Int us = INT_INTOBJ(ELM_PLIST(state,2));
-  if (s < 0 || us < 0 || us > 999999)
-    return Fail;
-  SyInstallAlarm(s, 1000*us);
-  return True;
-}
-
 
 /****************************************************************************
  **
@@ -4071,11 +4043,6 @@ static StructGVarFunc GVarFuncs [] = {
        FuncREADLINEINITLINE, "src/sysfiles.c:FuncREADLINEINITLINE" },
 #endif
 
-    {"STOP_TIMEOUT", 0, "",
-     FuncSTOP_TIMEOUT, "src/sysfiles.c:FuncSTOP_TIMEOUT" },
-
-    {"RESUME_TIMEOUT", 1, "state",
-     FuncRESUME_TIMEOUT, "src/sysfiles.c:FuncRESUME_TIMEOUT" },
 
 
     { 0 } };