Microsoft KB Archive/166282

= FIX: C2440 Caused by Template Function with Const Pointer =

Article ID: 166282

Article Last Modified on 7/5/2005

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APPLIES TO


 * Microsoft Visual C++ 4.2 Enterprise Edition
 * Microsoft Visual C++ 4.2 Professional Edition
 * Microsoft Visual C++ 4.2 Enterprise Edition
 * Microsoft Visual C++ 4.2 Professional Edition
 * Microsoft Visual C++ 5.0 Enterprise Edition
 * Microsoft Visual C++ 5.0 Professional Edition

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This article was previously published under Q166282



SYMPTOMS
The compiler generates the error C2440, when compiling a template function with a const pointer of class T as an argument, where class T is a template parameter.

C2440: 'conversion' : cannot convert from 'type1' to 'type2'



RESOLUTION
Starting with Visual C++ 5.0, explicitly specify the template arguments when calling the template function.

The sample code below demonstrates the problem and the workaround.



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:

170365 INFO: Visual Studio 97 Service Packs - What, Where, and Why



MORE INFORMATION
The following sample code demonstrates the problem.

Sample Code
/*  * Compiler Options: None */

template  T* func(const T*p) {     return 0; }

int main {     const int *i=0; int*j = func(i);   // erroneous C2440 here

return 0 ; } The following sample code demonstrates the workaround for Visual C++ 5.0.

Sample Code
/*  * Compiler Options: None */

template  T* func(const T*p) {     return 0; }

int main {     const int *i=0; int*j = func (i);

return 0 ; }

Additional query words: CL

Keywords: kbbug kbfix kblangcpp kbvs97sp1fix kbprogramming kbcpponly kbcode kbcompiler KB166282

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