.WEAK specifies symbols that are either defined externally in
    another module or defined globally in the current module. .WEAK
    suppresses any object library search for the symbol.

    When .WEAK specifies a symbol that is not defined in the current
    module, the symbol is externally defined. If the linker finds the
    symbol's definition in another module, it uses that definition.
    If the linker does not find an external definition, the symbol
    has a value of 0 and the linker does not report an error. The
    linker does not search a library for the symbol, but if a module
    brought in from a library for another reason contains the symbol
    definition, the linker uses it.

    When .WEAK specifies a symbol that is defined in the current
    module, the symbol is considered to be globally defined. However,
    if this module is inserted in an object library, this symbol
    is not inserted in the library's symbol table. Consequently,
    searching the library at link time to resolve this symbol does
    not cause the module to be included.