Inside Macintosh: Mac OS Runtime Architectures /

Chapter 5 - CFM-68K Runtime Conventions / Routine Calling Conventions

Variable-Argument Passing Conventions

When passing variable arguments, padding is added to some data types when pushing them onto the stack:

• Parameters of types UInt8, SInt8, UInt16, SInt16, and Boolean are converted to type SInt32 (as if by assignment) and pushed onto the stack as a 4-byte integer data item.
• Both float and double parameters are pushed onto the stack as 8-byte double data items (float data types are converted to type double (as if by assignment) before being pushed).
• All other data types are passed normally.