INFO: Old Style (K&R) Declarations Are Not Supported in C++

ID: Q79845

The information in this article applies to:

The Microsoft C/C++ Compiler (CL.EXE)
- Microsoft C/C++ for MS-DOS, version 7.0
- Microsoft Visual C++ for Windows, 16-bit edition, versions 1.0, 1.5
- Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 2.1, 4.0, 5.0

SUMMARY

The Microsoft C/C++ Compiler versions 7.0 and later do not support Old Style function declarations in C++ files. Old Style declarations are still supported in C files.

Old Style declarations, sometimes called K&R declarations, are declarations in which there are no parameters listed inside the parentheses. For example:


void KRfunc();  /* declaration */ 
void KRfunc(a, b)   /* definition */ 
int a;
char b;
{ }

C++ requires ANSI-style function prototypes (or declarations), which list the type of each parameter accepted by the function, as shown here:


   void ANSIfunc(int a, char b);

This type of declaration is required because in C++ each function has a signature. The signature consists of the name of the function and the types of the parameters it accepts. The compiler cannot construct the signature of a function from the K&R declaration.

REFERENCES

For more information about parameter lists in function declarations and how these are handled by C and C++, please see the following article in the Microsoft Knowledge Base:

Q94579 Creating a Function Pointer to a C++ Member Function

Additional query words:

Keywords : kbLangCPP kbVC100 kbVC150 kbVC200 kbVC210 kbVC400 kbVC500
Version : MS-DOS:7.0; WINDOWS:1.0,1.5; WINDOWS NT:1.0,2.0,2.1,4.0,5.0
Platform : MS-DOS NT WINDOWS
Issue type : kbinfo