remove overzealous sizeof() usage

Author: nmwsharp

src/file_helpers.cpp

@@ -40,9 +40,10 @@ std::string promptForFilename(std::string initName) {
   using namespace std::placeholders;
 
   // Register the callback which creates the UI and does the hard work
-  char* textBuff = new char[2048];
-  snprintf(textBuff, sizeof(textBuff), "%s", initName.c_str());
-  auto func = std::bind(filenamePromptCallback, textBuff, 2048);
+  const size_t BUFF_LEN = 2048;
+  char* textBuff = new char[BUFF_LEN];
+  snprintf(textBuff, BUFF_LEN, "%s", initName.c_str());
+  auto func = std::bind(filenamePromptCallback, textBuff, BUFF_LEN);
   pushContext(func);
 
   std::string stringOut(textBuff);