National Instruments 320685D-01 ユーザーズマニュアル

Chapter 1

LabWindows/CVI Compiler

©

 National Instruments Corporation

1-3

LabWindows/CVI Programmer Reference Manual

however, set options to cause the calling convention to default to __

stdcall

. The behavior 

is the same in LabWindows/CVI. You can set the default calling convention to either __

cdecl

 

or 

__stdcall

 using the Compiler Options command in the Options menu of the Project 

window. When you create a new project, the default calling convention is 

__cdecl

.

In Watcom C/C++, the default calling convention is not __

cdecl

 or 

__stdcall

. You must 

use the 

-4s

 (80486 Stack-Based Calling) option when you compile a module in Watcom for 

use in LabWindows/CVI. Refer to the 

 section in 

Chapter 3, 

. The 

-4s

 option causes the stack-based 

calling convention to be the default. In LabWindows/CVI under Watcom compatibility mode, 
the default calling convention is always the stack-based convention. It cannot be changed. The 
LabWindows/CVI compiler accepts the 

__cdecl

 and 

__stdcall

 conventions under 

Watcom, except that floating point and structure return values do not work in the 

__cdecl

 

calling convention. National Instruments recommends that you avoid using 

__cdecl

 with 

Watcom.

In the 

__cdecl

 calling convention and the Watcom stack-based calling convention, the 

calling function is responsible for cleaning up the stack. Functions can have a variable number 
of arguments.

In the 

__stdcall

 calling convention, the called function is responsible for cleaning up the 

stack. Functions with a variable number of arguments do not work in 

__stdcall

. If you use 

the 

__stdcall

 qualifier on a function with a variable number of arguments, 

LabWindows/CVI does not honor the qualifier. All compilers pass parameters and return 
values in the same way for 

__stdcall

 functions, except for floating point and structure 

return values.

National Instruments recommends the 

__stdcall

 calling convention for all functions 

exported from a DLL, except functions with a variable number of arguments. Visual Basic 
and other non-C Windows programs expect DLL functions to be 

__stdcall

.

You can use the following qualifiers in variable and function declarations:

__declspec(dllimport)

__declspec(dllexport)

__import

__export

_import

_export

00ProRef.book : 06chap01.fm  Page 3  Monday, March 9, 1998  3:23 PM