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random_r doesn't necessarily provide enough bits even for a fixnum (issue #668)

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Alex Shinn 2020-07-13 10:27:04 +09:00
parent 9940e0d053
commit b4fb077fef
1 changed files with 7 additions and 2 deletions
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9
lib/srfi/27/rand.c
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@ -55,7 +55,8 @@ typedef unsigned int sexp_random_t;
sexp sexp_rs_random_integer (sexp ctx, sexp self, sexp_sint_t n, sexp rs, sexp bound) { sexp sexp_rs_random_integer (sexp ctx, sexp self, sexp_sint_t n, sexp rs, sexp bound) {
sexp res; sexp res;
sexp_int32_t m; int64_t m;
sexp_int32_t m2;
#if SEXP_USE_BIGNUMS #if SEXP_USE_BIGNUMS
sexp_uint_t mod; sexp_uint_t mod;
sexp_uint32_t *data; sexp_uint32_t *data;
@ -67,7 +68,11 @@ sexp sexp_rs_random_integer (sexp ctx, sexp self, sexp_sint_t n, sexp rs, sexp b
if (sexp_unbox_fixnum(bound) <= 0) { if (sexp_unbox_fixnum(bound) <= 0) {
res = sexp_xtype_exception(ctx, self, "random bound must be positive", bound); res = sexp_xtype_exception(ctx, self, "random bound must be positive", bound);
} else { } else {
sexp_call_random(rs, m); /* ensure we have sufficient bits */
for (i=m=0; i <= 1<<(CHAR_BIT*sizeof(m))/RAND_MAX; ++i) {
sexp_call_random(rs, m2);
m = m * RAND_MAX + m2;
}
res = sexp_make_fixnum(m % sexp_unbox_fixnum(bound)); res = sexp_make_fixnum(m % sexp_unbox_fixnum(bound));
} }
#if SEXP_USE_BIGNUMS #if SEXP_USE_BIGNUMS