Q50234: Using Function Name Without "()" Produces No Code

Article: Q50234
Product(s): Microsoft C Compiler
Version(s): 1.0,1.5,2.0,4.0,6.0,6.0a,6.0ax
Operating System(s): 
Keyword(s): kbCompiler
Last Modified: 22-JUL-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft C/C++ Compiler (CL.EXE), included with:
   - Microsoft C for MS-DOS, versions 6.0, 6.0a, 6.0ax 
   - Microsoft C for OS/2, versions 6.0, 6.0a 
   - Microsoft C/C++ for MS-DOS, version 7.0 
   - Microsoft Visual C++, versions 1.0, 1.5 
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, versions 1.0, 2.0, 4.0 
-------------------------------------------------------------------------------

SUMMARY
=======

The information in this article is included in the documentation starting with
Visual C++ 5.0. Look there for future revisions.


When a function name declared in your program is used without parentheses, the
compiler does not produce any code. The compiler may not produce error messages
or warnings as long as the function has been prototyped. This occurs regardless
of whether or not the function takes parameters because the compiler calculates
the function address; however, because the function call operator "()" is not
present, no call is made. This result is similar to the following:

     int a;

     a;      /* no code generated here either */ 

In Microsoft C versions 6.0, 6.0a, and 6.0ax, the following warning is generated
on warning level 4:

  warning C4205: statement has no effect

In Microsoft C/C++ version 7.0, 16-bit Visual C++ version 1.XX, and 32-bit Visual
C++ version 1.0, using warning level 4 generates the following:

  warning C4705: statement has no effect with /W4

The warning is only generated when compiling with the optimizing compiler and
does not occur if the fast (/f) compiler is used.

In Microsoft 32-bit Visual C++ versions 2.0 and above, even using warning level 4
generates no diagnostic output. No warning issued, no code is produced.

MORE INFORMATION
================

The sample code below compiles and links correctly without errors but produces
no code in reference to myfunc(). For this to work correctly, add the function
call operator "()".

Sample Code
-----------

  /* Compiler Options needed: /W4     (C6.0, C6.0a, C6.0ax and 8.00 for
                                       Visual C++ for Windows NT)
                              /f- /W4 (7.0, and 8.0 for Visual C++
                                       for Windows)
  */ 

  void funcname(int a, int b);
  void main(void)
  {
       funcname;   /* Using myfunc without function call operator () */ 
  }

Additional query words: 1.00 1.50 2.00 4.00 6.00 6.00a 6.00ax 7.00 8.00 8.00c 9.00

======================================================================
Keywords          : kbCompiler 
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : :1.0,1.5,2.0,4.0,6.0,6.0a,6.0ax

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.