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

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index 06dfad2153440b67c04ff43cdeaa55d35a78a82e..4740e79ea92f8caaac85c5e4eac0367241b20b5c 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -900,10 +900,7 @@ void Isolate::BuildName(const char* name_prefix) {
     name_ = strdup(name_prefix);
     return;
   }
-  const char* kFormat = "%s-%lld";
-  intptr_t len = OS::SNPrint(NULL, 0, kFormat, name_prefix, main_port()) + 1;
-  name_ = reinterpret_cast<char*>(malloc(len));
-  OS::SNPrint(name_, len, kFormat, name_prefix, main_port());
+  name_ = OS::SNCreate(NULL, "%s-%" Pd64 "", name_prefix, main_port());
 }