Issue 0089: When does multiple definitions of a macro require a diagnositc message?

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: Fixed
Fixed in: C90 TC2
Converted from: dr.htm, dr_089.html

Item 26 - multiple definitions of macros

Consider the following code:

#define macro   object_like
 #define macro(argument)        function_like

Does this code require a diagnostic?

The wording of subclause 6.8.3 specifies that a macro may be redefined under certain circumstances (basically identical definitions), but does not actually forbid any other redefinition. Thus it can be argued that the constraint in subclause 6.8.3 is not violated, and a diagnostic is not required.

Comment from WG14 on 1997-09-23:

Correction

In subclause 6.8.3, page 89, change, in both paragraphs 2 and 3:

may be redefined by another #define preprocessing directive provided that

to:

shall not be redefined by another #define preprocessing directive unless