Use errorFn for runtime errors.

src/vm/wren_compiler.c

@@ -1,5 +1,6 @@
 #include <errno.h>
 #include <stdbool.h>
+#include <stdio.h>
 #include <string.h>
 
 #include "wren_common.h"
@@ -400,7 +401,8 @@ static void printError(Parser* parser, int line, const char* label,
   length += vsprintf(message + length, format, args);
   ASSERT(length < ERROR_MESSAGE_SIZE, "Error should not exceed buffer.");
   
-  parser->vm->config.errorFn(parser->module->name->value, line, message);
+  parser->vm->config.errorFn(WREN_ERROR_COMPILE,
+                             parser->module->name->value, line, message);
 }
 
 // Outputs a compile or syntax error. This also marks the compilation as having

src/vm/wren_debug.c

@@ -2,17 +2,21 @@
 
 #include "wren_debug.h"
 
-void wrenDebugPrintStackTrace(ObjFiber* fiber)
+void wrenDebugPrintStackTrace(WrenVM* vm)
 {
+  // Bail if the host doesn't enable printing errors.
+  if (vm->config.errorFn == NULL) return;
+  
+  ObjFiber* fiber = vm->fiber;
   if (IS_STRING(fiber->error))
   {
-    fprintf(stderr, "%s\n", AS_CSTRING(fiber->error));
+    vm->config.errorFn(WREN_ERROR_RUNTIME, NULL, -1, AS_CSTRING(fiber->error));
   }
   else
   {
     // TODO: Print something a little useful here. Maybe the name of the error's
     // class?
-    fprintf(stderr, "[error object]\n");
+    vm->config.errorFn(WREN_ERROR_RUNTIME, NULL, -1, "[error object]");
   }
 
   for (int i = fiber->numFrames - 1; i >= 0; i--)
@@ -30,8 +34,8 @@ void wrenDebugPrintStackTrace(ObjFiber* fiber)
     
     // -1 because IP has advanced past the instruction that it just executed.
     int line = fn->debug->sourceLines.data[frame->ip - fn->code.data - 1];
-    fprintf(stderr, "[%s line %d] in %s\n",
-            fn->module->name->value, line, fn->debug->name);
+    vm->config.errorFn(WREN_ERROR_STACK_TRACE, fn->module->name->value, line,
+                       fn->debug->name);
   }
 }
 

src/vm/wren_debug.h

@@ -4,10 +4,10 @@
 #include "wren_value.h"
 #include "wren_vm.h"
 
-// Prints the current stack trace for [fiber] to stderr.
+// Prints the stack trace for the current fiber.
 //
 // Used when a fiber throws a runtime error which is not caught.
-void wrenDebugPrintStackTrace(ObjFiber* fiber);
+void wrenDebugPrintStackTrace(WrenVM* vm);
 
 // The "dump" functions are used for debugging Wren itself. Normal code paths
 // will not call them unless one of the various DEBUG_ flags is enabled.

src/vm/wren_value.c

@@ -1,5 +1,6 @@
 #include <math.h>
 #include <stdarg.h>
+#include <stdio.h>
 #include <string.h>
 
 #include "wren.h"

src/vm/wren_vm.c

@@ -388,7 +388,7 @@ static void runtimeError(WrenVM* vm)
   }
 
   // If we got here, nothing caught the error, so show the stack trace.
-  wrenDebugPrintStackTrace(vm->fiber);
+  wrenDebugPrintStackTrace(vm);
   vm->fiber = NULL;
 }