Compiler Warning (level 4) C4209

nonstandard extension used : benign typedef redefinition

A type was redefined to be the same type as in the first definition.

The following is an example of this error:

typedef long lPulseWidth;
typedef long lPulseWidth;  // warning

This extension can prevent your code from being portable to other compilers and will generate an error under the /Za command-line option.