INFO: No Warning If Parameter Redeclared Using the Old Style

• The Microsoft C/C++ Compiler (CL.EXE) included with: - Microsoft C for MS-DOS, versions 6.0, 6.0a, 6.0ax - Microsoft C for OS/2, versions 6.0, 6.0a - 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

SUMMARY

In situations where the so-called "old-style" or "K&R-type" function declarations are used, the C compiler does not generate a warning when formal parameters are declared twice, even if they are redeclared with different types. This is expected behavior because one of the declarations is ignored when this type of function declaration is used. If ANSI-style, prototyped function declarations are used, a warning will be generated for any redeclarations.

MORE INFORMATION

The following code sample demonstrates this redeclaration problem:

Sample Code

   int func1(x, y)
   int x;
   long y;
   float x;       /* x is redeclared here, but no warning is given */
   {
      return (int)(x + y);
   }

   warning C4131: 'func1' : uses old-style declarator

   The use of function definitions with separate parameter identifier
   and declaration lists (not prototype-format parameter type and
   identifier declarators) is an obsolescent feature.