ilogb inconsistent with lrint, lroundThis issue has been automatically converted from the original issue lists and some formatting may not have been preserved.
Authors: WG 14, Fred J. Tydeman (USA)
Date: 2012-01-11
Reference document: N1595
Submitted against: C11 / C17
Status: Fixed
Fixed in: C17
Converted from: n2396.htm
For the case of converting a large finite value to an integer value, lrint and lround have one set of requirements, while ilogb has another set. This is inconsistent.
Both 7.12.9.5 The lrint and llrint functions and 7.12.9.7 The lround and llround functions have:
If the rounded value is outside the range of the return type, the numeric result is unspecified and a domain error or range error may occur.
While 7.12.6.5 The ilogb functions has:
If the correct value is outside the range of the return type, the numeric result is unspecified.
I believe that the following changes to C11 should be done.
7.12.6.5 The ilogb functions:
Change to: If the correct value is outside the range of the return type, the numeric result is unspecified and a domain error or range error may occur.
Comment from WG14 on 2017-11-03:
Feb 2012 meeting
Committee discussion
- Some believe the rationale presented as a reason for doing this is not a valid rationale for the change.
Proposed Technical Corrigendum
In 7.12.6.5 paragraph 2, change the last sentence to:
If the correct value is outside the range of the return type, the numeric result is unspecified and a domain error or range error may occur.