Like the scope, the linkage of a variable
declared extern depends on the placement of the declaration
in the program text. If the variable declaration appears outside of
any function definition and has been declared static earlier
in the file, the variable has internal linkage; otherwise, it has
external linkage in most cases. All object declarations that occur
outside a function and that do not contain a storage class specifier
declare identifiers with external linkage.
For objects in the unnamed namespace,
the linkage may be external, but the name is unique, and so from the
perspective of other translation units, the name effectively has internal
linkage.
Like the scope, the linkage of a variable
declared extern depends on the placement of the declaration
in the program text. If the variable declaration appears outside of
any function definition and has been declared static earlier
in the file, the variable has internal linkage; otherwise, it has
external linkage in most cases. All object declarations that occur
outside a function and that do not contain a storage class specifier
declare identifiers with external linkage.
For objects in the unnamed namespace,
the linkage may be external, but the name is unique, and so from the
perspective of other translation units, the name effectively has internal
linkage.