Compiler Warning (level 1, Error) C4233
nonstandard extension used: 'keyword' keyword only supported in C++, not C
The compiler compiled your source code as C rather than C++, and you used a keyword that is only valid in C++. The compiler compiles your source file as C if the extension of the source file is .c or you use /Tc.
This warning is always issued as an error. Use the warning pragma to disable.