Issue 0086: At object-like macros in system headers conforming?

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

Authors: Clive Feather, WG14
Date: 1993-12-03
Submitted against: C90
Status: Closed
Converted from: dr.htm, dr_086.html

Item 23 - object-like macros in system headers

Consider an implementation where <string.h> defines the macro strlen thus:

#define strlen  __internal_fast_strlen

and declares functions (defined elsewhere) called __internal_fast_strlen and strlen, both with the functionality of strlen in subclause 7.11.6.3. Is such an implementation conforming with respect to the rules of subclause 7.1.7?

Note that a strictly conforming application can detect this situation by comparing the value of the expression strlen taken before and after a #undef.

Comment from WG14 on 1997-09-23:

Response

The question asks whether a system header can define the name of a library function as an object-like macro, and cites subclause 7.1.7 as not using the term “function-like.”

The Committee notes the absence of this term, but also notes that subclause 7.1.7 requires that the macro definition always be suppressed when not followed by an open parenthesis. Therefore such macros must either be function-like, or the implementation must cause them to act as function-like macros.