Submitter: UK C Panel
Submission Date: 2001-09-07
Source: Clive D.W. Feather <clive@demon.net>
Version: 1.1
Date: 2002-03-07
Subject: all-zero bits representations
Consider the code:
int v [10];
memset (v, 0, sizeof v);
Most programmers would expect this code to set all the elements of v to zero. However, the code is actually undefined: it is possible for int to have a representation in which all-bits-zero is a trap representation (for example, if there is an odd-parity bit in the value).
Consider also:
int *p;
p = calloc (n_members, sizeof (int));
This problem applies to all integer types except for unsigned char. I believe that the idiom is well-enough known that it should be made a part of the Standard.
Suggested Technical Corrigendum
Append to 6.2.6.2#5:
For any integer type, the object representation where all the bits are zero shall be a representation of the value zero in that type.
Technical Corrigendum
Append to 6.2.6.2#5:
For any integer type, the object representation where all the bits are zero shall be a representation of the value zero in that type.