From c9634766e00d6a1e55c6471007f69b52f36ea7d1 Mon Sep 17 00:00:00 2001
From: Thomas Jentzsch <tjentzsch@yahoo.de>
Date: Tue, 13 Aug 2019 17:27:23 +0200
Subject: [PATCH] fix #393 by using one-shot breakpoints

---
 src/debugger/Debugger.cxx | 20 +++++++++++++++++++-
 src/debugger/Debugger.hxx |  1 +
 src/emucore/M6502.cxx     |  9 ++++++++-
 src/emucore/M6502.hxx     |  5 ++++-
 src/emucore/tia/TIA.cxx   | 10 ----------
 src/emucore/tia/TIA.hxx   |  6 ------
 6 files changed, 32 insertions(+), 19 deletions(-)

diff --git a/src/debugger/Debugger.cxx b/src/debugger/Debugger.cxx
index 3592ebc2e..8915fbc6a 100644
--- a/src/debugger/Debugger.cxx
+++ b/src/debugger/Debugger.cxx
@@ -196,6 +196,12 @@ PackedBitArray& Debugger::breakPoints() const
   return mySystem.m6502().breakPoints();
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+PackedBitArray& Debugger::breakPointFlags() const
+{
+  return mySystem.m6502().breakPointFlags();
+}
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 TrapArray& Debugger::readTraps() const
 {
@@ -329,8 +335,18 @@ int Debugger::trace()
     uInt64 startCycle = mySystem.cycles();
     int targetPC = myCpuDebug->pc() + 3; // return address
 
+    // set temporary breakpoint at target PC (if not existing already)
+    breakPoints().initialize();
+    if(!breakPoints().isSet(targetPC))
+    {
+      breakPoints().set(targetPC);
+      breakPointFlags().initialize();
+      breakPointFlags().set(targetPC);
+    }
+
     unlockSystem();
-    myOSystem.console().tia().updateScanlineByTrace(targetPC).flushLineCache();
+    mySystem.m6502().execute(11900000); // max. ~10 seconds
+    myOSystem.console().tia().flushLineCache();
     lockSystem();
 
     addState("trace");
@@ -345,6 +361,7 @@ void Debugger::toggleBreakPoint(uInt16 bp)
 {
   breakPoints().initialize();
   breakPoints().toggle(bp);
+  breakPointFlags().initialize();
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -353,6 +370,7 @@ void Debugger::setBreakPoint(uInt16 bp, bool set)
   breakPoints().initialize();
   if(set) breakPoints().set(bp);
   else    breakPoints().clear(bp);
+  breakPointFlags().initialize();
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
diff --git a/src/debugger/Debugger.hxx b/src/debugger/Debugger.hxx
index 6c6a21050..c71311ddf 100644
--- a/src/debugger/Debugger.hxx
+++ b/src/debugger/Debugger.hxx
@@ -150,6 +150,7 @@ class Debugger : public DialogContainer
     TiaOutputWidget& tiaOutput() const  { return myDialog->tiaOutput(); }
 
     PackedBitArray& breakPoints() const;
+    PackedBitArray& breakPointFlags() const;
     TrapArray& readTraps() const;
     TrapArray& writeTraps() const;
 
diff --git a/src/emucore/M6502.cxx b/src/emucore/M6502.cxx
index 2fff129ea..f6f468715 100644
--- a/src/emucore/M6502.cxx
+++ b/src/emucore/M6502.cxx
@@ -282,7 +282,14 @@ inline void M6502::_execute(uInt64 cycles, DispatchResult& result)
 
         if(myBreakPoints.isInitialized() && myBreakPoints.isSet(PC)) {
           myLastBreakCycle = mySystem->cycles();
-          result.setDebugger(currentCycles, "BP: ", PC);
+          // disable a one-shot breakpoint
+          if(myBreakPoints.isInitialized() && myBreakPointFlags.isSet(PC))
+          {
+            myBreakPoints.clear(PC);
+            myBreakPointFlags.clear(PC);
+          }
+          else
+            result.setDebugger(currentCycles, "BP: ", PC);
           return;
         }
 
diff --git a/src/emucore/M6502.hxx b/src/emucore/M6502.hxx
index ba10f138e..84672c378 100644
--- a/src/emucore/M6502.hxx
+++ b/src/emucore/M6502.hxx
@@ -213,6 +213,8 @@ class M6502 : public Serializable
     void attach(Debugger& debugger);
 
     PackedBitArray& breakPoints() { return myBreakPoints; }
+    // flags used for one-shot breakpoints
+    PackedBitArray& breakPointFlags() { return myBreakPointFlags; }
     TrapArray& readTraps() { return myReadTraps; }
     TrapArray& writeTraps() { return myWriteTraps; }
 
@@ -426,7 +428,8 @@ class M6502 : public Serializable
     Debugger* myDebugger;
 
     // Addresses for which the specified action should occur
-    PackedBitArray myBreakPoints;// , myReadTraps, myWriteTraps, myReadTrapIfs, myWriteTrapIfs;
+    PackedBitArray myBreakPoints;
+    PackedBitArray myBreakPointFlags;
     TrapArray myReadTraps, myWriteTraps;
 
     // Did we just now hit a trap?
diff --git a/src/emucore/tia/TIA.cxx b/src/emucore/tia/TIA.cxx
index 8a3797bbd..3713cf98c 100644
--- a/src/emucore/tia/TIA.cxx
+++ b/src/emucore/tia/TIA.cxx
@@ -1171,16 +1171,6 @@ TIA& TIA::updateScanlineByStep()
   return *this;
 }
 
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-TIA& TIA::updateScanlineByTrace(int target)
-{
-  uInt32 count = 10000;  // only try up to 10000 steps
-  while (mySystem->m6502().getPC() != target && count-- &&
-         mySystem->m6502().execute(1));
-
-  return *this;
-}
-
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt8 TIA::registerValue(uInt8 reg) const
 {
diff --git a/src/emucore/tia/TIA.hxx b/src/emucore/tia/TIA.hxx
index 1a1c15818..6c7f1aaee 100644
--- a/src/emucore/tia/TIA.hxx
+++ b/src/emucore/tia/TIA.hxx
@@ -471,12 +471,6 @@ class TIA : public Device
     */
     TIA& updateScanlineByStep();
 
-    /**
-      This method should be called to update the TIA with a new partial
-      scanline by tracing to target address.
-    */
-    TIA& updateScanlineByTrace(int target);
-
     /**
       Retrieve the last value written to a certain register.
     */