INFO: Character Parameters May Be Prototyped as Integers

• The C Run-Time (CRT), included with:
  • Microsoft C for MS-DOS, versions 5.1, 6.0, 6.0a, 6.0ax
  • Microsoft C for OS/2, versions 5.1, 6.0, 6.0a
  • 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, 4.0, 5.0, 6.0

SUMMARY

In Microsoft C, there are some functions in the run-time library that take character values as parameters (for example, memccpy, memset, and so on) and that are prototyped as taking integers. This is not a documentation error and your program will work correctly if a character value is passed in the place of the integer parameter (automatic type conversion takes care of this).

The integer value is specified because when the compiler pushes parameters on the stack so that the function being called can use them, it always pushes them in integer sized increments. In a 16-bit program where an integer is 2 bytes, 2 bytes will be pushed on the stack regardless of whether the value is an integer or a character. In a 32-bit program where an integer is always 4 bytes, 4 bytes will be pushed on the stack regardless of whether the value is an integer, long, short, or character.

Therefore, to simplify, the function is prototyped as receiving an integer.

Additional query words:

Keywords : kbCRT kbVC kbVC100 kbVC150 kbVC200 kbVC400 kbVC500 kbVC600
Version : MS-DOS:5.1,6.0,6.00a,6.00ax,7.0; OS/2:5.1,6.0,6.00a; WINDOWS:1.0,1.5; WINDOWS NT:1.0,2.0,4.0,5.0
Platform : MS-DOS NT OS/2 WINDOWS
Issue type : kbinfo