diff options
Diffstat (limited to 'lib/mini-gmp.c')
| -rw-r--r-- | lib/mini-gmp.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/lib/mini-gmp.c b/lib/mini-gmp.c index ea037b801dc..69a72bfd460 100644 --- a/lib/mini-gmp.c +++ b/lib/mini-gmp.c @@ -172,12 +172,19 @@ see https://www.gnu.org/licenses/. */ } \ } while (0) +/* If mp_limb_t is of size smaller than int, plain u*v implies + automatic promotion to *signed* int, and then multiply may overflow + and cause undefined behavior. Explicitly cast to unsigned int for + that case. */ +#define gmp_umullo_limb(u, v) \ + ((sizeof(mp_limb_t) >= sizeof(int)) ? (u)*(v) : (unsigned int)(u) * (v)) + #define gmp_udiv_qrnnd_preinv(q, r, nh, nl, d, di) \ do { \ mp_limb_t _qh, _ql, _r, _mask; \ gmp_umul_ppmm (_qh, _ql, (nh), (di)); \ gmp_add_ssaaaa (_qh, _ql, _qh, _ql, (nh) + 1, (nl)); \ - _r = (nl) - _qh * (d); \ + _r = (nl) - gmp_umullo_limb (_qh, (d)); \ _mask = -(mp_limb_t) (_r > _ql); /* both > and >= are OK */ \ _qh += _mask; \ _r += _mask & (d); \ @@ -198,7 +205,7 @@ see https://www.gnu.org/licenses/. */ gmp_add_ssaaaa ((q), _q0, (q), _q0, (n2), (n1)); \ \ /* Compute the two most significant limbs of n - q'd */ \ - (r1) = (n1) - (d1) * (q); \ + (r1) = (n1) - gmp_umullo_limb ((d1), (q)); \ gmp_sub_ddmmss ((r1), (r0), (r1), (n0), (d1), (d0)); \ gmp_umul_ppmm (_t1, _t0, (d0), (q)); \ gmp_sub_ddmmss ((r1), (r0), (r1), (r0), _t1, _t0); \ |