How to suppress warnings about unused variables in C++?

Question

How can one suppress warnings compiler generates about unused variables in a c++ program?

I am using g++ compiler

Answer 1

Put in a cast to void:

int unused;
(void)unused;

Answer 2

Compile with the -Wno-unused-variable option.

See the GCC documentation on Warning Options for more information.

The -Wno-__ options turn off the options set by -W__. Here we are turning off -Wunused-variable.

Also, you can apply the __attribute__((unused)) to the variable (or function, etc.) to suppress this warning on a case-by-case basis. Thanks Jesse Good for mentioning this.