Issue 0039.01: Must MB_CUR_MAX be one in the "C" locale?

This issue has been automatically converted from the original issue lists and some formatting may not have been preserved.

Authors: Vania Joloboff, WG14
Date: 1992-12-10
Reference document: X3J11/91-061
Submitted against: C90
Status: Closed
Converted from: dr.htm, dr_039.html

My interpretation of the Standard is that the value of MB_CUR_MAX must be one in the "C" locale. I infer that from the fact that:

1. The characters in the "C" locale must be alphanumeric + space.
2. The isXXX functions specify character constant values for the "C" locale.
3. A character constant consists of one or more characters that are enclosed within apostrophes. A character is regarded as having type char.
4. The data type char consists of one byte of storage.

However this clarification should be made explicit.

Comment from WG14 on 1997-09-23:

Response

In fact 3, we presume the second sentence was intended to be: “A character constant is regarded as having type char,” in order to be applicable to this request. That is not true; a character constant is of type int. Also facts 1-4 deal with the single-byte chars and not the extended character set.

In any case, the facts as listed do not logically lead to the conclusion that MB_CUR_MAX must be one (1) in the "C" locale. In fact, this conclusion is not true. It is possible for MB_CUR_MAX to be greater than one in the "C" locale. In subclause 7.10, page 149, MB_CUR_MAX is “the maximum number of bytes in a multibyte character for the extended character set specified by the current locale.” In subclause 7.4.1.1, page 107, the "C" locale is “the minimal environment for C translation.” The minimal environment may still require more than one byte for multibyte characters.