Assignment of Void Pointer Does Not Give Warning Message

MS-DOS                 | OS/2       | WINDOWS        | WINDOWS NT

The information in this article applies to:

• The Microsoft C/C++ Compiler (CL.EXE) included with:

      - Microsoft C for MS-DOS, versions 6.0, 6.0a, and 6.0ax
      - Microsoft C for OS/2, versions 6.0, and 6.0a
      - Microsoft C/C++ for MS-DOS, version 7.0
      - Microsoft Visual C++ for Windows, versions 1.0, 1.5, and 1.51
      - Microsoft Visual C++ 32-bit Edition, version 1.0, 2.0, and 2.1
  

SUMMARY

The Sample Code below shows an inconsistency with the way that the Microsoft compilers listed above deal with pointer checking. The ANSI standard is unclear about whether an assignment to a void pointer should be checked to see if it is being assigned a nonpointer variable. The code below shows that character pointers are checked while void pointers are not; the code will generate the following warnings:

16-bit compilers

The compiler generates the following warning for the void pointer in the sample code as well as the character pointer:

   C4047: '=' different levels of indirection

32-bit compilers

The compiler generates the following warming with the sample code:

   C4047: "=": 'void *' differs in levels of indirection from 'int'

7.0 and later

Compiler versions 7.0 and later generate the following error in both cases if the program is compiled as a C++ program (.cpp extension).

   error C2446: '=' : no conversion from 'int ' to 'void *'

MORE INFORMATION

Sample Code:

/* Compile options needed: none
*/

int i;         /* i could be float, double, char, long, or unsigned */
char *p;
void *v;

void main()

   p = i;      /* This will give a warning message */
   v = i;