Article: Q100832
Product(s): Microsoft C Compiler
Version(s): 1.0,2.0,4.0,5.0,6.0
Operating System(s):
Keyword(s): kbCompiler kbVC600
Last Modified: 26-MAR-2002
-------------------------------------------------------------------------------
The information in this article applies to:
- Microsoft Visual C++, versions 1.0, 2.0, 4.0
- Microsoft Visual C++, 32-bit Enterprise Edition, versions 5.0, 6.0
- Microsoft Visual C++, 32-bit Professional Edition, versions 5.0, 6.0
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0
- Microsoft Visual C++.NET (2002)
-------------------------------------------------------------------------------
NOTE: Microsoft Visual C++ NET (2002) supported both the managed code model that is provided by the .NET Framework and the unmanaged native Windows code model. The information in this article applies to unmanaged Visual C++ code only.
SUMMARY
=======
Visual C++,32-bit Edition, supports three calling conventions: C (_cdecl),
standard (_stdcall), and fastcall (_fastcall). The compiler does not support the
Pascal calling convention (_pascal) provided by Microsoft compilers for MS-DOS
and 16-bit Windows.
The following table summarizes the calling conventions:
_cdecl _stdcall _fastcall
-------------------------------------------------------------------
Arguments Pushed R to L Pushed R to L Note 3
Stack cleaned up by Caller Called Called
Naming convention Prepend "_" Note 1 Note 2
Note 1: The _stdcall calling convention decorates each function name by
prepending an underscore character (as the _cdecl convention does) and
appending an at sign "@" and the decimal representation of the number of
bytes of stack space required. Each argument is widened to a multiple of four
bytes.
Note 2: The _fastcall calling convention decorates each function name by
prepending an at sign "@" and appending an at sign and the decimal
representation of the number of bytes of stack space required. Each argument
is widened to a multiple of four bytes.
Note 3: The first two function arguments that require four or fewer bytes are
placed into registers. The caller pushes the remainder of the parameters onto
the stack from right to left. This behavior may change in future versions.
The default calling convention is _cdecl. If an application declares a function
that accepts a variable number of arguments with the _fastcall or _stdcall
calling convention, the compiler uses the _cdecl calling convention for that
function.
MORE INFORMATION
================
The following code examples illustrate the code generated in the calling
function and in the called function to support the C calling convention:
int _cdecl CFunc(int a, int b);
calling function called function
-------------------------------------------
push b _CFunc PROC NEAR
push a .
call _CFunc .
add esp,8 .
. RET
. _CFunc ENDP
.
int _cdecl CVarFunc(int a, ...);
calling function called function
-------------------------------------------
push ... _CVarFunc PROC NEAR
push a .
call _CVarFunc .
add esp,4+... .
. RET
. _CVarFunc ENDP
.
The following code example illustrates the code generated in the calling function
and in the called function to support the standard calling convention:
int _stdcall StdFunc(int a, int b);
calling function called function
-------------------------------------------
push b _StdFunc@8 PROC NEAR
push a .
call _StdFunc@8 .
. .
. RET 8
. _StdFunc@8 ENDP
The following code example illustrates the code generated in the calling function
and in the called function to support the fastcall calling convention:
int _fastcall FastFunc(int a, int b);
calling function called function
-------------------------------------------
mov edx, b @FastFunc@8 PROC NEAR
mov ecx, a .
call @FastFunc@8 .
. .
. RET 8
. @FastFunc@8 ENDP
Additional query words:
======================================================================
Keywords : kbCompiler kbVC600
Technology : kbVCsearch kbVC400 kbAudDeveloper kbvc100 kbVC500 kbVC600 kbVC200 kbVC32bitSearch kbVCNET kbVC500Search
Version : :1.0,2.0,4.0,5.0,6.0
Issue type : kbinfo
=============================================================================