Use the /f option to compile source files without any default optimizations. It generates the _FAST preprocessor constant. Programs compiled with /f are slower and larger but compile in less time than the optimizing compiler requires; this option is useful during the development process. If used, the /f option must be the first option on the command line. The Fast Compile option does not support initialized static huge data.
Note that with Microsoft C/C++, the /f option supersedes the /qc option.