Re: C/C++ calling convention
On Aug 31, 8:15 am, Nick Keighley <nick_keighley_nos...@hotmail.com>
wrote:
On 25 Aug, 15:44, Goran Pusic <gor...@cse-semaphore.com> wrote:
Any compiler provides you with a way to specify what calling
convention you want from a list of calling conventions
chosen by that compiler (look for e.g. __cdecl).
you mean *all* compilers provide you with a way of secifying
calling conventions? I find that surprising.
They're required to by the standard. All compilers are required
to support both ``extern "C"'' and ``extern "C++"''. Most do
this in a standard conformant manner, and don't support anything
else, however.
But it depends on the platform. The Intel architecture has
hardware support for cleaning up the stack when returning from a
function. To use it, however, the function must always be
called with the same number of bytes as arguments; it doesn't
work with varargs. The C standard added the requirement that
when calling a varargs function, a declaration for it must be in
scope, so that one could use the hardware support most of the
time, and skip it when the function used varargs. Historically,
however, this came too late. The intelligent solution is to use
the vararg convention for C, and the hardware support for C++
(which requires a function declaration to be in scope for all
functions), but all modern compilers follow Microsoft rather
than doing this. (The old Zortech C++ compiler did this, using
a different calling convention for C and for C++. And passing
the address of a C++ function to a function expecting a pointer
to a C function would cause a crash.)
--
James Kanze