Template Version: @(#)sac_nextcase 1.68 02/23/09 SMI
This information is Copyright 2009 Sun Microsystems
1. Introduction
1.1. Project/Component Working Name:
sys/stdbool.h
1.2. Name of Document Author/Supplier:
Author: Garrett D'Amore
1.3 Date of This Document:
10 August, 2009
4. Technical Description
I am sponsoring this fast track for Roland Mainz. The case times out in one
week (8/19/2009), and minor binding is requested.
-- Garrett
1. Introduction
This case a new header <sys/stdbool.h> to allow kernel code
to use the C99 datatype "bool" and the associated values
"true" and "false".
The committment level of these interfaces is "Committed".
The release binding is "minor".
2. Discussion
We need to move <stdbool.h> to <sys/stdbool.h> (and create a new
<stdbool.h> which sources <sys/stdbool.h>) that (new [2]) kernel
code can use the new C99 datatype "bool" ([1]) ?
[1]="bool" differs from the traditional kernel-land "boolean_t"
datatype that it is smaller (e.g. |sizeof(boolean_t)==sizeof(int)|
vs. |sizeof(bool)==1|) and optionally allows the compiler to do
better optimisations on this datatype (since it is allowed to
assume that it only contains "true" and "false" as values instead
of the full range from |INT_MIN|-|INT_MAX| for "boolean_t" (since
this |enum| is treated as |int| by value-range optimisations))
and usually reduces the size of executables (see CR #6870093).
[2]=Note that we do not intend do force developers to replace
"boolean_t" in existing code, only allow that new code or changes
(optionally) can use this C99 feature.
3. Interface table
Interface | committment level
-----------------------------------------------+------------------
<sys/stdbool.h> | Commited
C99 datatype "bool" | Commited
C99 value "true" | Commited
C99 value "false" | Commited
C99 CPP symbol "__bool_true_false_are_defined" | Commited
Notes:
1. <sys/stdbool.h> precisely implements the functionality for
<stdbool.h> defined in IEEE Std 1003.1-2001.
2. The ability to undefine and redefine the macros "bool",
"true", and "false" is an _implementation_detail_ in the ISO C
standard which may be withdrawn in a future version of the
standards specifications, kernel code shall _not_ rely on this
_implementation_detail_ (e.g. "#undef true", "#undef false",
"#undef bool" are not allowed in kernel code as they may cause
problems with future compiler versions).
4. References
- Bugster CR #6870093 RFE: C99 <stdbool.h> should be visible for
kernel modules
- IEEE Std 1003.1-2001
- http://en.wikipedia.org/wiki/Stdbool.h
- ISO C99 draft (final document is not available for free)
http://www.open-std.org/JTC1/SC22/WG14/www/docs/n1256.pdf
5. Manual page differences
None required.
6. Resources and Schedule
6.4. Steering Committee requested information
6.4.1. Consolidation C-team Name:
ON
6.5. ARC review type: FastTrack
6.6. ARC Exposure: open
