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

runtime/vm/stack_frame_test.cc

Index: runtime/vm/stack_frame_test.cc
diff --git a/runtime/vm/stack_frame_test.cc b/runtime/vm/stack_frame_test.cc
index 426ede7941ffca93ce17712d3daea40db621e633..319a66efdab96c28e9689d288bc5ebdc910d88a8 100644
--- a/runtime/vm/stack_frame_test.cc
+++ b/runtime/vm/stack_frame_test.cc
@@ -101,10 +101,9 @@ void FUNCTION_NAME(StackFrame_validateFrame)(Dart_NativeArguments args) {
       const Library& lib = Library::Handle(Library::LookupLibrary(url));
       ASSERT(!lib.IsNull());
       const char* lib_name = String::Handle(lib.url()).ToCString();
-      intptr_t length = OS::SNPrint(NULL, 0, "%s_%s", lib_name, expected_name);
-      char* full_name = Thread::Current()->zone()->Alloc<char>(length + 1);
-      ASSERT(full_name != NULL);
-      OS::SNPrint(full_name, (length + 1), "%s_%s", lib_name, expected_name);
+      char* full_name = NULL;
+      SNPRINT(full_name, Thread::Current()->zone()->Alloc<char>, "%s_%s",
+              lib_name, expected_name);
       if (strcmp(full_name, name) != 0) {
         FATAL("StackFrame_validateFrame fails, incorrect frame.\n");
       }