Issue 0116: Is a diagnostic required when the address of a reigister arry is implicitly taken?

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

Authors: Ron Guilmette, WG14
Date: 1993-12-03
Submitted against: C90
Status: Closed
Cross-references: 0017.06
Converted from: dr.htm, dr_116.html

ANSI/ISO C Defect Report #rfg23:

Subject: Implicit unary & applied to register arrays.

a) Does the following code involve usage which requires a diagnostic from a conforming implementation?

b) Does the following code involve usage which renders the code itself not strictly conforming?

void example ()
        {
        register int array[5] = 0;

        array;     /* ? */
        array[3];  /* ? */
        array+3;   /* ? */
        }

Background:

Subclause 6.5.1 (footnotes):

The implementation may treat any register declaration simply as an auto declaration. However whether or not addressable storage is actually used, the address of any part of an object declared with storage-class specifier register may not be computed, either explicitly (by use of the unary & operator as discussed in 6.3.3.2) or implicitly (by converting an array name to a pointer as discussed in 6.2.2.1). Thus the only operator that can be applied to an array declared with storage-class specifier register is sizeof.

This footnote, while offering guidance, doesn't really answer the question of whether or not an implementation is required to issue a diagnostic for the case where the address of a register array is implicitly taken (as discussed in subclause 6.2.2.1). Nor does it definitively answer the question of whether such code should be considered to be strictly conforming or not.

(Reference: CIB #1, RFI #17, question #6.)

Comment from WG14 on 1997-09-23:

Response

a) No, a diagnostic is not required.

b) Yes, this renders the program not strictly conforming.