soft-fp should round floating pointer numbers according to the current
rounding mode. However, in the current code of lrint() and llrint(),
there are if statements before the actual rounding computation
if(j0 < -1)
return 0;
Where j0 is the exponent of the floating point number.
It means any number having a exponent less than -1
(i.e. interval (-0.5, 0.5)) will be rounded to 0 regardeless of the
rounding mode.
The bug already fixed in glibc in 2006 by moving the check afterwards
the rounding computation, but still persists in newlib.
This patch fixed it in a similar way to glibc
Ref Commit in glibc: 6624dbc07b5a9fb316ed188ef01f65b8eea8b47c
* libm/common/s_lrint.c (lrint): Annotate shift operations with
possible shift amount ranges, and use SAFE_RIGHT_SHIFT to avoid
undefined behaviour.
* libm/common/s_llrint.c (llrint): Likewise.
* libm/common/s_lround.c (lround): Correct some comments on ranges.
* libm/common/s_llround.c (llround): Likewise.
Jesse Huang via Newlib
Matthias Kannwischer
Jeff Johnston