Re: [PATCH ] PR libstdc++/60037 - SIGFPE in std::generate_canonical

[Ed Smith-Rowland]

On 07/29/2014 04:29 AM, Jonathan Wakely wrote:

On 29/07/14 04:11 -0400, Ed Smith-Rowland wrote:

As discussed in the audit trail both _Adaptor and generate_canonical are both meant to use floating point values. Both are here given static_asserts to that effect.

This would have prevented this error and might help future users.

The main issue is the use of value_type in _Adaptor and thus in generate_canonical in hypergeometric_distribution::operator(). This distribution is a discreet distribution and thus value_type is an unsigned integer which caused overflow in generate_canonical. In keeping with practice in all other discreet distributions a double type will now be used in _Adaptor.

Someday, it might be beneficial to discuss an _IntegralAdaptor and a corresponding __generate_canonical for use in our discreet distributions but I want to close this bug with this patch.

Makes sense, thanks for the fix.

Built and tested on x86_64-linux.

OK?

One question ...

Index: testsuite/ext/random/hypergeometric_distribution/pr60037.cc
===================================================================

--- testsuite/ext/random/hypergeometric_distribution/pr60037.cc (revision 0) +++ testsuite/ext/random/hypergeometric_distribution/pr60037.cc (working copy)

@@ -0,0 +1,24 @@
+// { dg-options "-std=gnu++11" }
+// { dg-require-cstdint "" }
+// { dg-require-cmath "" }
+// { dg-options "-O0" }

Did you mean to have two separate dg-options directives here?

OK to commit, after either combining them into one or removing the
second one.

Committed (with small changes to test cases).
Attached new CLand patch.

2014-07-29  Ed Smith-Rowland  <3dw...@verizon.net>

        PR libstdc++/60037 - SIGFPE in std::generate_canonical<unsigned int...>
        * include/bits/random.h (_Adaptor): static_assert for non floating-point
        result type.
        * include/bits/random.tcc (generate_canonical): Ditto.
        * include/ext/random.tcc (hypergeometric_distribution::operator()):
        Use double as a rng result type.
        * testsuite/26_numerics/random/pr60037-neg.cc: New.
        * testsuite/ext/random/hypergeometric_distribution/pr60037.cc: New.


Index: include/bits/random.h
===================================================================
--- include/bits/random.h       (revision 213145)
+++ include/bits/random.h       (working copy)
@@ -164,6 +164,8 @@
     template<typename _Engine, typename _DInputType>
       struct _Adaptor
       {
+       static_assert(std::is_floating_point<_DInputType>::value,
+                     "template argument not a floating point type");
 
       public:
        _Adaptor(_Engine& __g)
Index: include/bits/random.tcc
===================================================================
--- include/bits/random.tcc     (revision 213145)
+++ include/bits/random.tcc     (working copy)
@@ -3463,6 +3463,9 @@
     _RealType
     generate_canonical(_UniformRandomNumberGenerator& __urng)
     {
+      static_assert(std::is_floating_point<_RealType>::value,
+                   "template argument not a floating point type");
+
       const size_t __b
        = std::min(static_cast<size_t>(std::numeric_limits<_RealType>::digits),
                    __bits);
Index: include/ext/random.tcc
===================================================================
--- include/ext/random.tcc      (revision 213145)
+++ include/ext/random.tcc      (working copy)
@@ -1355,7 +1355,7 @@
       operator()(_UniformRandomNumberGenerator& __urng,
                 const param_type& __param)
       {
-       std::__detail::_Adaptor<_UniformRandomNumberGenerator, result_type>
+       std::__detail::_Adaptor<_UniformRandomNumberGenerator, double>
          __aurng(__urng);
 
        result_type __a = __param.successful_size();
Index: testsuite/26_numerics/random/pr60037-neg.cc
===================================================================
--- testsuite/26_numerics/random/pr60037-neg.cc (revision 0)
+++ testsuite/26_numerics/random/pr60037-neg.cc (working copy)
@@ -0,0 +1,15 @@
+// { dg-do compile }
+// { dg-options "-std=gnu++11" }
+
+#include <random>
+
+std::mt19937 urng;
+
+std::__detail::_Adaptor<std::mt19937, unsigned long> aurng(urng);
+
+auto x = std::generate_canonical<std::size_t,
+                       std::numeric_limits<std::size_t>::digits>(urng);
+
+// { dg-error "static assertion failed: template argument not a floating point 
type" "" { target *-*-* } 167 }
+
+// { dg-error "static assertion failed: template argument not a floating point 
type" "" { target *-*-* } 3466 }
Index: testsuite/ext/random/hypergeometric_distribution/pr60037.cc
===================================================================
--- testsuite/ext/random/hypergeometric_distribution/pr60037.cc (revision 0)
+++ testsuite/ext/random/hypergeometric_distribution/pr60037.cc (working copy)
@@ -0,0 +1,23 @@
+// { dg-options "-std=gnu++11 -O0" }
+// { dg-require-cstdint "" }
+// { dg-require-cmath "" }
+
+#include <ext/random>
+#include <functional>
+
+void
+hyperplot(unsigned int N, unsigned int K, unsigned int n)
+{
+  std::mt19937 re; // the default engine
+  __gnu_cxx::hypergeometric_distribution<> hd(N, K, n);
+  auto gen = std::bind(hd, re);
+  gen();
+}
+
+int
+main()
+{
+  hyperplot(15, 3, 2);
+  hyperplot(500, 50, 30);
+  hyperplot(100, 20, 5);
+}