Q51474: INFO: Character Parameters May Be Prototyped as Integers

Article: Q51474
Product(s): Microsoft C Compiler
Version(s): 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.
Operating System(s): 
Keyword(s): kbCRT kbVC kbVC100 kbVC150 kbVC200 kbVC400 kbVC500 kbVC600
Last Modified: 25-JUL-2001

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The information in this article applies to:

- 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 
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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:

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Keywords          : kbCRT kbVC kbVC100 kbVC150 kbVC200 kbVC400 kbVC500 kbVC600 
Technology        : kbVCsearch kbAudDeveloper kbCRT
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
Issue type        : kbinfo

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