The multiplication (4 * _M_t * __1p) can wraparound to zero if _M_t is
unsigned and 4 * _M_t wraps to zero. The third operand has type double,
so do the second multiplication first, so that we aren't multiplying
integers.
libstdc++-v3/ChangeLog:
PR libstdc++/114359
* include/bits/random.tcc (binomial_distribution::param_type):
Ensure arithmetic is done as type double.
* testsuite/26_numerics/random/binomial_distribution/114359.cc: New test.
// sqrt(pi / 2)
const double __spi_2 = 1.2533141373155002512078826424055226L;
_M_s1 = std::sqrt(__np * __1p) * (1 + _M_d1 / (4 * __np));
- _M_s2 = std::sqrt(__np * __1p) * (1 + _M_d2 / (4 * _M_t * __1p));
+ _M_s2 = std::sqrt(__np * __1p) * (1 + _M_d2 / (4 * (_M_t * __1p)));
_M_c = 2 * _M_d1 / __np;
_M_a1 = std::exp(_M_c) * _M_s1 * __spi_2;
const double __a12 = _M_a1 + _M_s2 * __spi_2;
--- /dev/null
+// { dg-do run { target c++11 } }
+
+// Bug 114359 - std::binomial_distribution hangs in infinite loop
+
+#include <random>
+
+int main()
+{
+ std::default_random_engine g{};
+ std::binomial_distribution<std::uint32_t> b(1U << 30);
+ b(g); // hangs forever
+}