nonstandard extension 'single line comment' was used
A single-line comment, which is a Microsoft extension to C (but standard in C++), was used in a C source file.
If the /Za (disable Microsoft extensions) option has been specified, this condition generates a syntax error.
To disable this warning, insert #pragma warning(disable:4001) into your code. See #pragma warning in the Preprocessor Reference for more information.
The following is an example of this warning:
int i; // warning
int j; /* no warning */