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| author | vlefevre <vlefevre@280ebfd0-de03-0410-8827-d642c229c3f4> | 2020-03-24 15:32:22 +0000 |
|---|---|---|
| committer | vlefevre <vlefevre@280ebfd0-de03-0410-8827-d642c229c3f4> | 2020-03-24 15:32:22 +0000 |
| commit | 610e574fc2bf49bcf6a7f98f0fe6513fd24652e2 (patch) | |
| tree | 45e3444b947a9a7c9eee6c36fb73fc92212ef67b | |
| parent | b523c7635a6e15f474d67ae9ce044a907dde0b5a (diff) | |
| download | mpfr-610e574fc2bf49bcf6a7f98f0fe6513fd24652e2.tar.gz | |
[src/sub1.c] If exp_b = MPFR_EXP_MIN, an integer overflow may occur in
the "MAX (aq, bq) + 2 <= diff_exp" branch. This is possible only with
UBF. Fixed this bug with an early underflow detection in the UBF case.
git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@13806 280ebfd0-de03-0410-8827-d642c229c3f4
| -rw-r--r-- | src/sub1.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/src/sub1.c b/src/sub1.c index 78458a0db..0256e43cd 100644 --- a/src/sub1.c +++ b/src/sub1.c @@ -96,6 +96,15 @@ mpfr_sub1 (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mpfr_rnd_t rnd_mode) if (MPFR_UNLIKELY (MPFR_IS_UBF (b) || MPFR_IS_UBF (c))) { exp_b = MPFR_UBF_GET_EXP (b); + /* Early underflow detection. Rare, but a test is needed anyway + since in the "MAX (aq, bq) + 2 <= diff_exp" branch, the exponent + may decrease and MPFR_EXP_MIN would yield an integer overflow. */ + if (MPFR_UNLIKELY (exp_b < __gmpfr_emin - 1)) + { + if (rnd_mode == MPFR_RNDN) + rnd_mode = MPFR_RNDZ; + return mpfr_underflow (a, rnd_mode, MPFR_SIGN(a)); + } diff_exp = mpfr_ubf_diff_exp (b, c); MPFR_LOG_MSG (("UBF: exp_b=%" MPFR_EXP_FSPEC "d%s " "diff_exp=%" MPFR_EXP_FSPEC "d%s\n", |