[committed 1/2] libstdc++: Fix deserialization for std::normal_distribution [PR105502]

[Jonathan Wakely via Gcc-patches]

Tested powerpc64le-linux, pushed to trunk. Backports to all branches
needed.

-- >8 --

This fixes a regression in std::normal_distribution deserialization that
caused the object to be left unchanged if the __state_avail value read
from the stream was false.

libstdc++-v3/ChangeLog:

        PR libstdc++/105502
        * include/bits/random.tcc
        (operator>>(basic_istream<C,T>&, normal_distribution<R>&)):
        Update state when __state_avail is false.
        * 
testsuite/26_numerics/random/normal_distribution/operators/serialize.cc:
        Check that deserialized object equals serialized one.
---
 libstdc++-v3/include/bits/random.tcc          |  2 +-
 .../operators/serialize.cc                    | 36 ++++++++++++++++++-
 2 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/include/bits/random.tcc 
b/libstdc++-v3/include/bits/random.tcc
index 6c72e991007..87a16a21336 100644
--- a/libstdc++-v3/include/bits/random.tcc
+++ b/libstdc++-v3/include/bits/random.tcc
@@ -1961,7 +1961,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       bool __saved_avail;
       if (__is >> __mean >> __stddev >> __saved_avail)
        {
-         if (__saved_avail && (__is >> __x._M_saved))
+         if (!__saved_avail || (__is >> __x._M_saved))
            {
              __x._M_saved_available = __saved_avail;
              __x.param(param_type(__mean, __stddev));
diff --git 
a/libstdc++-v3/testsuite/26_numerics/random/normal_distribution/operators/serialize.cc
 
b/libstdc++-v3/testsuite/26_numerics/random/normal_distribution/operators/serialize.cc
index 9d8f8278fb3..d4f9f374643 100644
--- 
a/libstdc++-v3/testsuite/26_numerics/random/normal_distribution/operators/serialize.cc
+++ 
b/libstdc++-v3/testsuite/26_numerics/random/normal_distribution/operators/serialize.cc
@@ -25,6 +25,7 @@
 
 #include <random>
 #include <sstream>
+#include <testsuite_hooks.h>
 
 void
 test01()
@@ -37,10 +38,43 @@ test01()
   str << u;
 
   str >> v;
+  VERIFY( u == v );
+}
+
+void
+test_pr105502()
+{
+  // PR libstdc++/105502 std::normal_distribution deserialization issue
+  std::stringstream str;
+  std::normal_distribution<> d{1, 2}, d2;
+  std::minstd_rand0 g;
+  str << d;
+  VERIFY( str );
+  str >> d2;
+  VERIFY( str );
+  VERIFY( d == d2 );
+
+  (void) d(g); // sets d._M_saved_available = true
+  str.str("");
+  str.clear();
+  str << d;
+  VERIFY( str );
+  str >> d2;
+  VERIFY( str );
+  VERIFY( d == d2 );
+
+  (void) d(g); // sets d._M_saved_available = false
+  str.str("");
+  str.clear();
+  str << d;
+  VERIFY( str );
+  str >> d2;
+  VERIFY( str );
+  VERIFY( d == d2 );
 }
 
 int main()
 {
   test01();
-  return 0;
+  test_pr105502();
 }
-- 
2.34.1