Uses SNPRINT macro where possible. Otherwise uses #define for format.

runtime/vm/debugger.cc

Index: runtime/vm/debugger.cc
diff --git a/runtime/vm/debugger.cc b/runtime/vm/debugger.cc
index 96966d92ae1c690d3c5604c088c7a414dd6ea5cf..50aa858b36f59331feadd7828ba8d47b989887e3 100644
--- a/runtime/vm/debugger.cc
+++ b/runtime/vm/debugger.cc
@@ -403,17 +403,11 @@ const char* Debugger::QualifiedFunctionName(const Function& func) {
   Class& func_class = Class::Handle(func.Owner());
   String& class_name = String::Handle(func_class.Name());
 
-  const char* kFormat = "%s%s%s";
-  intptr_t len = OS::SNPrint(NULL, 0, kFormat,
-      func_class.IsTopLevel() ? "" : class_name.ToCString(),
-      func_class.IsTopLevel() ? "" : ".",
-      func_name.ToCString());
-  len++;  // String terminator.
-  char* chars = Thread::Current()->zone()->Alloc<char>(len);
-  OS::SNPrint(chars, len, kFormat,
-              func_class.IsTopLevel() ? "" : class_name.ToCString(),
-              func_class.IsTopLevel() ? "" : ".",
-              func_name.ToCString());
+  char* chars = NULL;
+  SNPRINT(chars, Thread::Current()->zone()->Alloc<char>, "%s%s%s",
+          func_class.IsTopLevel() ? "" : class_name.ToCString(),
+          func_class.IsTopLevel() ? "" : ".",
+          func_name.ToCString());
   return chars;
 }