OPTIONS(LINKAGE)

OPTIONS(LINKAGE) is an entry name attribute that specifies the calling convention. It can have the following attributes:

STDCALL (32-bit Windows only)
This option specifies the STDCALL linkage, the linkage convention used by Windows 32-bit APIs. It is treated as if SYSTEM was specified when running on 64-bit Windows and all supported 32-bit and 64-bit UNIX systems.
SYSTEM
This option specifies the default linkage used by the host system. It should not be used on 32-bit Windows.