DEFECT: _fp_round sets incorrect rounding mode.
AFFECTS: Rounding mode affects all floating-point computations and
narrowing conversions including int-to-float, double-to-float, and
longlong-to-double.
PRESENT IN: These PalmOS versions were available for test: 3.1.1 3.1H3 3.3 3.5
All tested versions have the defect.
TO REPLICATE: http://www.sleepless-night.com/cgi-bin/twiki/view/Main/_fp_roundB
ug
contains details, test results and a Quartus Forth script that
will
test for the defect.
SUMMARY: ToNearest rounding mode is active after a device reset. _fp_round can
then be used only to select TowardZero or Upward mode. Attempt to
select Downward mode gives Upward instead. Subsequent calls to
_fp_round can only produce Upward mode, regardless of the argument.
Only a reset can restore ToNearest mode.
RELATED PROBLEMS:
1. The _fp_round return value is shifted 4 bits, apparently a known issue but
contrary to documentation.
2. Allowing for the shift, the return value reflects the desired rounding mode
passed to _fp_round, falsely indicating that the desired mode has been
activated when in fact a different mode has been selected.
More details available in my first posting on the topic:
news:46710@palm-dev-forum
a/k/a http://www.escribe.com/computing/pcpqa/m38616.html
PLEASE ADVISE OF PATCH OR WORKAROUND AVAILABILITY:
How can an application select Downward rounding mode?
How can an application select ToNearest, TowardZero, or Downward mode
after another mode has been selected?
Will the defect be corrected in a future OS version?
Chapman Flack
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