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Q168008: FIX: C2166 Incorrect Type Deduction for Template Parameter

Article: Q168008
Product(s): Microsoft C Compiler
Version(s): 5.0
Operating System(s): 
Keyword(s): kbcode kberrmsg kbtool kbCompiler kbCPPonly kbLangCPP kbVC kbVC500bug kbVS97sp1fix
Last Modified: 17-JUL-2001

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

- Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
- Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

The compiler deduces incorrect type for a template parameter T, associated with
a template function that takes a const reference of type T, causing the compiler
error C2166 as follows:

  l-value specifies const object

RESOLUTION
==========

Do not use a literal when calling the template function. Instead, declare a
variable, and pass the variable as an argument to the template function.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This bug has been corrected in Visual Studio 97
Service Pack 1.

For additional information about the Visual Studio 97 Service Pack 1, please see
the following article in the Microsoft Knowledge Base:

  Q170365 INFO: Visual Studio 97 Service Packs - What, Where, and Why

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

The following sample demonstrates the problem and a workaround.

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

     /*
     * Compiler Options: None
     */ 

     #define BUG
     //Workaround: comment the line above
     //Uncomment the following line
     //#define WORKAROUND

     template<class T> void Test(const T& x)
     {
        T y = x;
        if(y < 0)
           y = -y;
     }

     int main()
     {
     #ifdef BUG
        Test(3) ;
     #endif

     #ifdef WORKAROUND
        int n = 3 ;
        Test(n) ;
     #endif

        return 0 ;
     }

Additional query words:

======================================================================
Keywords          : kbcode kberrmsg kbtool kbCompiler kbCPPonly kbLangCPP kbVC kbVC500bug kbVS97sp1fix 
Technology        : kbVCsearch kbAudDeveloper kbVC500 kbVC32bitSearch kbVC500Search
Version           : 5.0
Issue type        : kbbug
Solution Type     : kbfix

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

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