Add new debugger command 'stepwhile'.

This command steps through the code instruction-by-instruction (just like the
'step' command) while the <condition> argument evaluates to true. This is a
(pretty slow) workaround for breakpoints and the 'run' command which seems
broken from debugging scripts.

src/debugger/DebuggerParser.cxx

@@ -1766,6 +1766,23 @@ void DebuggerParser::executeStep()
     << "executed " << dec << debugger.step() << " cycles";
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// "stepwhile"
+void DebuggerParser::executeStepwhile()
+{
+  int res = YaccParser::parse(argStrings[0].c_str());
+  if(res != 0) {
+    commandResult << red("invalid expression");
+    return;
+  }
+  Expression* expr = YaccParser::getResult();
+  int ncycles = 0;
+  do {
+    ncycles += debugger.step();
+  } while (expr->evaluate());
+  commandResult << "executed " << ncycles << " cycles";
+}
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 // "tia"
 void DebuggerParser::executeTia()
@@ -2868,6 +2885,16 @@ DebuggerParser::Command DebuggerParser::commands[kNumCommands] = {
     std::mem_fn(&DebuggerParser::executeStep)
   },
 
+  {
+    "stepwhile",
+    "Single step CPU while <condition> is true",
+    "Example: stepwhile pc!=$f2a9",
+    true,
+    true,
+    { kARG_WORD, kARG_END_ARGS },
+    std::mem_fn(&DebuggerParser::executeStepwhile)
+  },
+
   {
     "tia",
     "Show TIA state",

src/debugger/DebuggerParser.hxx

@@ -66,7 +66,7 @@ class DebuggerParser
     string saveScriptFile(string file);
 
   private:
-    enum { kNumCommands = 91 };
+    enum { kNumCommands = 92 };
 
     // Constants for argument processing
     enum {
@@ -210,6 +210,7 @@ class DebuggerParser
     void executeSavestateif();
     void executeScanline();
     void executeStep();
+    void executeStepwhile();
     void executeTia();
     void executeTrace();
     void executeTrap();