DOCUMENT:Q98989  26-JUL-2001  [visualc]
TITLE   :FIX: Constructor C4705 Warning from Aggregate Class Member
PRODUCT :Microsoft C Compiler
PROD/VER::1.0,1.5,1.51,1.52,2.0,2.1,2.20
OPER/SYS:
KEYWORDS:kbCompiler kbCPPonly kbVCkbbuglist kbfixlist

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

 - Microsoft C/C++ Compiler (CL.EXE), included with:
    - Microsoft C/C++ for MS-DOS, version 7.0 
    - Microsoft Visual C++, versions 1.0, 1.5, 1.51, 1.52 
    - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, versions 1.0, 2.0, 2.1, 2.20 
-------------------------------------------------------------------------------

SYMPTOMS
========

When Microsoft C/C++ compiles an application, it generates the following message
for each class constructor:

   warning C4705: statement has no effect

CAUSE
=====

The source code has an embedded aggregate member (class, struct, or union) in a
class definition and the compiler command line includes the /W4 and /f- compiler
options. Note that the /f- option is not supported in the Microsoft Visual C++
32-bit compiler.

RESOLUTION
==========

The C4705 warning is incorrect and can be safely ignored. If the embedded
aggregate is a class, define a default constructor. This will supress the
warning.

STATUS
======

Microsoft has confirmed this to be a bug in the products listed at the beginning
of this article. This problem was fixed in Microsoft Visual C++, version 4.0.

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

The C4705 warning usually indicates a statement does not affect program
execution. Each of the following statements causes this particular warning:

      num - 1270;
      count != 15;
      42;

The code example below demonstrates a structure data member that generates the
C4705 warning for each class constructor. The warning also occurs if the example
used a class or a union instead of a structure.

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

   /* Compile options needed: /W4 /f- (Remove /f- for 32-bit compiler)
   */ 

   #include <iostream.h>

   struct MyStruct_tag { int i; };

   class CMyClass {
      private:
         MyStruct_tag MyStruct;
      public:
         inline CMyClass() { MyStruct.i = 0; };
         inline CMyClass(int init) { MyStruct.i = init; };
         void Print(const char *);
   };

   void CMyClass::Print(const char* string)
   {
      cout << string << MyStruct.i << endl;
   }

   void main(void)
   {
      CMyClass Object1;
      CMyClass Object2(1024);

      Object1.Print("Object1.MyStruct.i = ");
      Object2.Print("Object2.MyStruct.i = ");
   }

Additional query words: 7.00 8.00 8.00c 9.00 9.10 1.00 1.50 1.51 2.00 2.10 2.20

======================================================================
Keywords          : kbCompiler kbCPPonly kbVC kbbuglist kbfixlist
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : :1.0,1.5,1.51,1.52,2.0,2.1,2.20
Issue type        : kbbug
Solution Type     : kbfix

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

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