Article ID: 112337
Article Last Modified on 11/18/2003
APPLIES TO
- The C Run-Time (CRT), when used with:
- Microsoft Visual C++ 1.0 Professional Edition
- Microsoft Visual C++ 2.0 Professional Edition
This article was previously published under Q112337
SYMPTOMS
Attempting to replace the default _matherr function with a user-defined version and then linking with the C run-time dynamic-linked library (DLL) causes the compiler to issue the following warning:
Running the resultant executable causes the default _matherr to be used rather than the user-defined version.
CAUSE
The compiler issues the C4273 warning because of the way the _matherr function is prototyped in the MATH.H header file. _matherr has the following prototype:
_CRTIMP int __cdecl _matherr(struct _exception *);
When code is being compiled to be used with the C run-time DLL, _CRTIMP is defined to be the following:
__declspec(dllimport)
When code is being compiled to be used with one of the statically linked C run-time libraries, _CRTIMP is defined to be nothing.
The C4273 warning is generated because the compiler has detected a redefinition of _matherr after already seeing a prototype that specifies that _matherr is being imported.
RESOLUTION
It is not possible to replace the default version of _matherr when using the dynamically linked version of the C run-time library.
The README.WRI file supplied with Visual C++, 32-bit Edition, version 1.0, gives the following information:
Using _matherr with CRTDLL.DLL
If you use the dynamically linked version of the C run-time
library (CRTDLL.DLL), you cannot replace the default _matherr
routine with a user-defined version. You can only install a
custom _matherr routine if you use one of the statically linked C
run-time libraries.
CRTDLL.DLL is the name of the C Run-time DLL that is supplied with Windows NT. The C Run-time DLL supplied with version 1.0 of Visual C++, 32-bit Edition, is called MSVCRT10.DLL and the name of the C Run-time DLL supplied with version 2.0 of Visual C++, 32-bit Edition is MSVCRT20.DLL. The limitation of not being able to replace _matherr pertains only to using MSVCRT*.DLL.
MORE INFORMATION
The following sample code can be used to demonstrate the problem.
Sample Code
/* Compile options needed: /MD
*/
#include <math.h>
#include <string.h>
#include <stdio.h>
void main()
{
// Do a math operation that causes an error
printf( "log( -2.0 ) = %e\n", log( -2.0 ) );
}
int _matherr( struct _exception *except )
{
/* Handle _DOMAIN errors for log */
if( except->type == _DOMAIN )
{
if( strcmp( except->name, "log" ) == 0 )
{
except->retval = log( -(except->arg1) );
printf( "Special: using absolute value: %s: _DOMAIN "
"error\n", except->name );
return 1;
}
}
else
{
printf( "Normal: " );
return 0; /* Else use the default actions */
}
return 0;
}
REFERENCE
For additional information, please see the following article in the Microsoft Knowledge Base:
112297 INFO: User Defined CRT Function Causes Unresolved External
Additional query words: _matherrl
Keywords: kbcrt kbprb KB112337
