PRB: C4057 or C4133 Occur Unexpectedly

• The Microsoft C/C++ Compiler (CL.EXE) included with: - Microsoft C/C++ for MS-DOS, version 7.0 - Microsoft Visual C++ for Windows, versions 1.0, 1.5 - Microsoft Visual C++ 32-bit Edition, versions 1.0, 2.0, 4.0, 5.0

SYMPTOMS

Using the Microsoft C/C++ compiler (CL.EXE) versions 7.0, 8.0, and 8.0c for MS-DOS, the following warning is generated:

   C4057: 'argument': indirection to slightly different base types

   C4133: 'argument' : incompatible types-from 'short *' to 'int *'

   C4133: 'function' : incompatible types-from 'short *' to 'int *'

CAUSE

These warnings are expected behavior. According to ANSI standards, variables of type int* are different from variables of type short*. And, although the compiler may be able to perform an implicit promotion/demotion among intergral types (char, short, int, long, etc.), pointers are not of integral type.

RESOLUTION

To remove these warnings, use an appropriate cast to instruct the compiler to explicitly convert the value from its current data type to the desired.

MORE INFORMATION

The only restriction on the size of the short given by the ANSI standard is that it NOT be longer than an integer. Code should be written with this in mind so that it will be portable. In many implementations, such as WINDOWS NT, integers are not the same as shorts.

Compiling the following program will generate the discussed warning:

Sample Code

   /* Compile options needed: /c /W4
   */

   void ShortFunc( short, short * );
   void Func( int, int * );

   void main( )
   {
       short sTest;
       short *sPoint;

       ShortFunc( sTest, sPoint );
       Func( sTest, sPoint );  /*  Generates warning  */
       Func( sTest, (int *)sPoint );  /*  Does not generate warning  */
   }