Global const usage in C ++

C language habits, in C ++, there are some errors. An extern const is used in combination.

Using const directly in C ++ implies the meaning of static. The following program can be compiled in C language. However, in C ++, compilation fails. The Compiler used is mingw GCC or vs2008.

File a. cpp (or a. c)

Const int I = 123; // because the implicit meaning here is static const
...

File main. cpp (or main. c)

Extern const int I;

Int main ()

{

// When I is used here, C ++ will report an error when compiling to the connection process.

}

In C ++, the modification method is:

File a. cpp

Extern const int I = 60; // use extern to remove the implied static meaning of const

...

In C ++, the use of separate const globally implies that the local meaning of the file is static. If you want to use it in other files, the prefix extern is required.