First bits of external debugger API

runtime/bin/main.cc

Index: runtime/bin/main.cc
===================================================================
--- runtime/bin/main.cc	(revision 2184)
+++ runtime/bin/main.cc	(working copy)
@@ -7,6 +7,7 @@
 #include <stdio.h>
 
 #include "include/dart_api.h"
+#include "include/dart_debugger_api.h"
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
@@ -28,6 +29,12 @@
 static const char* generate_pprof_symbols_filename = NULL;
 
 
+// Global state that indicates whether there is a debug breakpoint.
+// This pointer points into an argv buffer and does not need to be
+// free'd.
+static const char* breakpoint_at = NULL;
+
+
 static bool IsValidFlag(const char* name,
                         const char* prefix,
                         intptr_t prefix_length) {
@@ -56,6 +63,16 @@
 }
 
 
+static bool ProcessDebugOption(const char* option) {
+  const char* kDebugOption = "--break_at=";
+  const char* func_name = ProcessOption(option, kDebugOption);
+  if (func_name != NULL) {
+    breakpoint_at = func_name;
+  }
+  return func_name != NULL;
+}
+
+
 // Parse out the command line arguments. Returns -1 if the arguments
 // are incorrect, 0 otherwise.
 static int ParseArguments(int argc,
@@ -73,10 +90,12 @@
   while ((i < argc) && IsValidFlag(argv[i], kPrefix, kPrefixLen)) {
     if (ProcessPprofOption(argv[i])) {
       i += 1;
-      continue;
+    } else if (ProcessDebugOption(argv[i])) {
+      i += 1;
+    } else {
+      vm_options->AddArgument(argv[i]);
+      i += 1;
     }
-    vm_options->AddArgument(argv[i]);
-    i += 1;
   }
   if (generate_pprof_symbols_filename != NULL) {
     Dart_InitPprofSupport();
@@ -329,7 +348,7 @@
     return 255;  // Indicates we encountered an error.
   }
 
-  // Lookup and invoke the top level main function.
+  // Lookup the library of the main script.
   Dart_Handle script_url = Dart_NewString(canonical_script_name);
   Dart_Handle library = Dart_LookupLibrary(script_url);
   if (Dart_IsError(library)) {
@@ -339,6 +358,35 @@
     free(canonical_script_name);
     return 255;  // Indicates we encountered an error.
   }
+  // Set debug breakpoint if specified on the command line.
+  if (breakpoint_at != NULL) {
+    char* bpt_function = strdup(breakpoint_at);
+    Dart_Handle class_name;
+    Dart_Handle function_name;
+    char* dot = strchr(bpt_function, '.');
+    if (dot == NULL) {
+      class_name = Dart_NewString("");
+      function_name = Dart_NewString(breakpoint_at);
+    } else {
+      *dot = '\0';
+      class_name = Dart_NewString(bpt_function);
+      function_name = Dart_NewString(dot + 1);
+    }
+    free(bpt_function);
+    Dart_Breakpoint bpt;
+    result = Dart_SetBreakpointAtEntry(
+                 library, class_name, function_name, &bpt);
+    if (Dart_IsError(result)) {
+      fprintf(stderr, "Error setting breakpoint at '%s': %s\n",
+          breakpoint_at,
+          Dart_GetError(result));
+      Dart_ExitScope();
+      Dart_ShutdownIsolate();
+      free(canonical_script_name);
+      return 255;  // Indicates we encountered an error.
+    }
+  }
+  // Lookup and invoke the top level main function.
   result = Dart_InvokeStatic(library,
                              Dart_NewString(""),
                              Dart_NewString("main"),