Xref: utzoo comp.lang.c:8790 comp.sys.ibm.pc:13988
Path: utzoo!utgpu!water!watmath!clyde!att-cb!att-ih!pacbell!ames!ncar!gatech!mcnc!decvax!decwrl!pyramid!prls!philabs!pwa-b!mmintl!franka
From: franka@mmintl.UUCP (Frank Adams)
Newsgroups: comp.lang.c,comp.sys.ibm.pc
Subject: Re: C declaration styles
Message-ID: <2801@mmintl.UUCP>
Date: 1 Apr 88 15:19:40 GMT
References: <1238@wjvax.UUCP> <297@ho7cad.ATT.COM>
Reply-To: franka@mmintl.UUCP (Frank Adams)
Organization: Ashton-Tate Corporation, East Hartford Development Center
Lines: 31

In article <297@ho7cad.ATT.COM> ekb@ho7cad.ATT.COM (Eric K. Bustad) writes:
>No one else has asked, so I guess that I must reveal my ignorance.
>Can someone explain the meaning of Microsoft's "cdecl" keyword?

Microsoft (and a number of other PC C vendors) supports two subroutine
calling conventions: "C" style and "Pascal" style.  The Pascal style
supports interface to Pascal, Fortran, and compiled Basic programs, as well
as OS/2 system functions.  The C style supports functions with a variable
number of arguments.

One can use the "pascal" keyword on a function declaration to specify that
it is to be called with the pascal convention.  Alternatively, one can use a
compile switch to default all functions to pascal.  In this case, it is
necessary to have a keyword to specify that a function is to use the C
convention.  "cdecl" is it.

(Some compilers support "fortran" as a synonym for "pascal".)

(For those who care: there are two major differences between the two
conventions.  In C style, the calling function removes the arguments from
the stack after the call; in Pascal style, the called function does so
before returning.  For C style, the arguments are pushed right to left;
Pascal style is left to right.  A minor difference is the way that struct
values longer than 4 bytes are returned: C style is for the called function
to put the result in static storage, and return a pointer to it; Pascal
style is for the calling function to pass an additional argument, the
address where the result is to be put.)
-- 

Frank Adams                           ihnp4!philabs!pwa-b!mmintl!franka
Ashton-Tate          52 Oakland Ave North         E. Hartford, CT 06108