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| author | Jonathan Wakely <jwakely@redhat.com> | 2024-03-18 13:22:17 +0000 |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2024-06-11 13:19:20 +0100 |
| commit | bd31ecc1c7aef5b4ae7ddb04926a2f4105957df4 (patch) | |
| tree | cf67bb2c5eeea7b406643740c20c41aa0336e3fc | |
| parent | 5c2c5805304da2436f4a749d357eee34eae9d792 (diff) | |
| download | gcc-bd31ecc1c7aef5b4ae7ddb04926a2f4105957df4.zip gcc-bd31ecc1c7aef5b4ae7ddb04926a2f4105957df4.tar.gz gcc-bd31ecc1c7aef5b4ae7ddb04926a2f4105957df4.tar.bz2 | |
libstdc++: Fix infinite loop in std::binomial_distribution [PR114359]
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.
(cherry picked from commit 07e03761a7fc1626a6a74ed957e117f56981558c)
| -rw-r--r-- | libstdc++-v3/include/bits/random.tcc | 2 | ||||
| -rw-r--r-- | libstdc++-v3/testsuite/26_numerics/random/binomial_distribution/114359.cc | 12 |
2 files changed, 13 insertions, 1 deletions
diff --git a/libstdc++-v3/include/bits/random.tcc b/libstdc++-v3/include/bits/random.tcc index 4164420..5d9f679 100644 --- a/libstdc++-v3/include/bits/random.tcc +++ b/libstdc++-v3/include/bits/random.tcc @@ -1503,7 +1503,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // 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; diff --git a/libstdc++-v3/testsuite/26_numerics/random/binomial_distribution/114359.cc b/libstdc++-v3/testsuite/26_numerics/random/binomial_distribution/114359.cc new file mode 100644 index 0000000..c1e4c38 --- /dev/null +++ b/libstdc++-v3/testsuite/26_numerics/random/binomial_distribution/114359.cc @@ -0,0 +1,12 @@ +// { 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 +} |