diff options
Diffstat (limited to 'mpfr/sub_one_ulp.c')
| -rw-r--r-- | mpfr/sub_one_ulp.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/mpfr/sub_one_ulp.c b/mpfr/sub_one_ulp.c index 36ed5620a..a14b35867 100644 --- a/mpfr/sub_one_ulp.c +++ b/mpfr/sub_one_ulp.c @@ -1,6 +1,6 @@ /* mpfr_sub_one_ulp -- subtract one unit in last place -Copyright 1999, 2001 Free Software Foundation, Inc. +Copyright 1999, 2001, 2002 Free Software Foundation, Inc. This file is part of the MPFR Library. @@ -41,17 +41,19 @@ mpfr_sub_one_ulp(mpfr_ptr x, mp_rnd_t rnd_mode) MPFR_ASSERTN(MPFR_PREC_MIN > 1); xn = 1 + (MPFR_PREC(x) - 1) / BITS_PER_MP_LIMB; - sh = xn * BITS_PER_MP_LIMB - MPFR_PREC(x); + sh = (mp_prec_t) xn * BITS_PER_MP_LIMB - MPFR_PREC(x); xp = MPFR_MANT(x); mpn_sub_1 (xp, xp, xn, MP_LIMB_T_ONE << sh); if (xp[xn-1] >> (BITS_PER_MP_LIMB - 1) == 0) { /* was an exact power of two: not normalized any more */ mp_exp_t exp = MPFR_EXP(x); - if (exp == __mpfr_emin) + /* Note: In case of underflow and rounding to the nearest mode, + x won't be changed. Beware of infinite loops! */ + if (exp == __gmpfr_emin) return mpfr_set_underflow(x, rnd_mode, MPFR_SIGN(x)); else { - int i; + mp_size_t i; MPFR_EXP(x)--; xp[0] = (sh + 1 == BITS_PER_MP_LIMB) ? 0 : MP_LIMB_T_MAX << (sh + 1); for (i = 1; i < xn; i++) |