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libstdc++: Add assertions for preconditions in sampling distributions [PR 82584] 

These three distributions all require 0 < S where S is the sum of the
weights. When the sum is zero there's an undefined FP division by zero.
Add assertions to help users diagnose the problem.

libstdc++-v3/ChangeLog:

	PR libstdc++/82584
	* include/bits/random.tcc
	(discrete_distribution::param_type::_M_initialize)
	(piecewise_constant_distribution::param_type::_M_initialize)
	(piecewise_linear_distribution::param_type::_M_initialize):
	Add assertions for positive sums..
	* testsuite/26_numerics/random/pr60037-neg.cc: Adjust dg-error
	line.
This commit is contained in:
Jonathan Wakely 2020-10-08 15:14:58 +01:00
parent 5a448362da
commit b2a96bf9dc
2 changed files with 4 additions and 1 deletions
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3
libstdc++-v3/include/bits/random.tcc
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@ -2630,6 +2630,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
const double __sum = std::accumulate(_M_prob.begin(),
_M_prob.end(), 0.0);
__glibcxx_assert(__sum > 0);
// Now normalize the probabilites.
__detail::__normalize(_M_prob.begin(), _M_prob.end(), _M_prob.begin(),
__sum);
@ -2794,6 +2795,7 @@ namespace __detail
const double __sum = std::accumulate(_M_den.begin(),
_M_den.end(), 0.0);
__glibcxx_assert(__sum > 0);
__detail::__normalize(_M_den.begin(), _M_den.end(), _M_den.begin(),
__sum);
@ -3016,6 +3018,7 @@ namespace __detail
_M_cp.push_back(__sum);
_M_m.push_back((_M_den[__k + 1] - _M_den[__k]) / __delta);
}
__glibcxx_assert(__sum > 0);
// Now normalize the densities...
__detail::__normalize(_M_den.begin(), _M_den.end(), _M_den.begin(),

2
libstdc++-v3/testsuite/26_numerics/random/pr60037-neg.cc
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@ -12,4 +12,4 @@ auto x = std::generate_canonical<std::size_t,
// { dg-error "static assertion failed: template argument must be a floating point type" "" { target *-*-* } 167 }
// { dg-error "static assertion failed: template argument must be a floating point type" "" { target *-*-* } 3281 }
// { dg-error "static assertion failed: template argument must be a floating point type" "" { target *-*-* } 3284 }