(nasm.info)Section 8.1.4


8.1.4. `c32.mac': Helper Macros for the 32-bit C Interface
----------------------------------------------------------

   Included in the NASM archives, in the `misc' directory, is a file
`c32.mac' of macros. It defines three macros: `proc', `arg' and
`endproc'. These are intended to be used for C-style procedure
definitions, and they automate a lot of the work involved in keeping
track of the calling convention.

   An example of an assembly function using the macro set is given here:

     proc    _proc32
     
     %$i     arg
     %$j     arg
             mov     eax,[ebp + %$i]
             mov     ebx,[ebp + %$j]
             add     eax,[ebx]
     
     endproc

   This defines `_proc32' to be a procedure taking two arguments, the
first (`i') an integer and the second (`j') a pointer to an integer. It
returns `i + *j'.

   Note that the `arg' macro has an `EQU' as the first line of its
expansion, and since the label before the macro call gets prepended to
the first line of the expanded macro, the `EQU' works, defining `%$i'
to be an offset from `BP'. A context-local variable is used, local to
the context pushed by the `proc' macro and popped by the `endproc'
macro, so that the same argument name can be used in later procedures.
Of course, you don't _have_ to do that.

   `arg' can take an optional parameter, giving the size of the
argument.  If no size is given, 4 is assumed, since it is likely that
many function parameters will be of type `int' or pointers.


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