C declaration styles

[Frank Adams]

In article <297 at ho7cad.ATT.COM> ekb at 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.)
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Frank Adams                           ihnp4!philabs!pwa-b!mmintl!franka
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