This section pertain only to Win32. On Win64 there is a single native calling convention. All convention specifiers are ignored on this platform.
When a subprogram F (caller) calls a subprogram G
(callee), there are several ways to push G‘s parameters on the
stack and there are several possible scenarios to clean up the stack
upon G‘s return. A calling convention is an agreed upon software
protocol whereby the responsibilities between the caller (F) and
the callee (G) are clearly defined. Several calling conventions
are available for Windows:
C (Microsoft defined)
Stdcall (Microsoft defined)
Win32 (GNAT specific)
DLL (GNAT specific)