Using Function Name Without "()" Produces No Code

MS-DOS                 | OS/2       | WINDOWS   | WINDOWS NT

The information in this article applies to:

   The Microsoft C/C++ Compiler (CL.EXE) included with:
    - Microsoft C for MS-DOS, versions 6.0, 6.0a, and 6.0ax
    - Microsoft C for OS/2, versions 6.0 and 6.0a
    - Microsoft C/C++ for MS-DOS, versions 7.0
    - Microsoft Visual C++ for Windows, versions 1.0 and 1.5
    - Microsoft Visual C++ 32-bit Edition, versions 1.0, 2.0, and 4.0

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

SUMMARY

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 */

   warning C4205: statement has no effect

   warning C4705: statement has no effect with /W4

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 () */
}