error: declaration does not declare anything [-fpermissive]

This error message typically occurs when a variable or function declaration is missing a data type or identifier.

For example, the following code will produce this error:

int; // missing identifier

void(); // missing function name

To fix the error, make sure that all variable and function declarations include a data type and identifier:

int x; // variable declaration with data type and identifier

void foo(); // function declaration with data type (void) and identifier (foo)

If you are still encountering the error, make sure that your code is properly formatted and that all necessary headers and libraries are included.