Fix PR#22433. The algorithm is_partitioned was testing an item in the middle of the sequence twice.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@227824 91177308-0d34-0410-b5e6-96231b3b80d8

include/algorithm

@@ -3148,6 +3148,9 @@ is_partitioned(_InputIterator __first, _InputIterator __last, _Predicate __pred)
     for (; __first != __last; ++__first)
         if (!__pred(*__first))
             break;
+    if ( __first == __last )
+        return true;
+    ++__first;
     for (; __first != __last; ++__first)
         if (__pred(*__first))
             return false;

test/std/algorithms/alg.modifying.operations/alg.partitions/is_partitioned.pass.cpp

@@ -17,6 +17,7 @@
 #include <cassert>
 
 #include "test_iterators.h"
+#include "counting_predicates.hpp"
 
 struct is_odd
 {
@@ -27,32 +28,50 @@ int main()
 {
     {
         const int ia[] = {1, 2, 3, 4, 5, 6};
+        unary_counting_predicate<is_odd, int> pred((is_odd()));
         assert(!std::is_partitioned(input_iterator<const int*>(std::begin(ia)),
                                     input_iterator<const int*>(std::end(ia)),
-                                    is_odd()));
+                                    std::ref(pred)));
+        assert(pred.count() <= std::distance(std::begin(ia), std::end(ia)));
     }
     {
         const int ia[] = {1, 3, 5, 2, 4, 6};
+        unary_counting_predicate<is_odd, int> pred((is_odd()));
         assert( std::is_partitioned(input_iterator<const int*>(std::begin(ia)),
                                     input_iterator<const int*>(std::end(ia)),
-                                    is_odd()));
+                                    std::ref(pred)));
+        assert(pred.count() <= std::distance(std::begin(ia), std::end(ia)));
     }
     {
         const int ia[] = {2, 4, 6, 1, 3, 5};
+        unary_counting_predicate<is_odd, int> pred((is_odd()));
         assert(!std::is_partitioned(input_iterator<const int*>(std::begin(ia)),
                                     input_iterator<const int*>(std::end(ia)),
-                                    is_odd()));
+                                    std::ref(pred)));
+        assert(pred.count() <= std::distance(std::begin(ia), std::end(ia)));
     }
     {
         const int ia[] = {1, 3, 5, 2, 4, 6, 7};
+        unary_counting_predicate<is_odd, int> pred((is_odd()));
         assert(!std::is_partitioned(input_iterator<const int*>(std::begin(ia)),
                                     input_iterator<const int*>(std::end(ia)),
-                                    is_odd()));
+                                    std::ref(pred)));
+        assert(pred.count() <= std::distance(std::begin(ia), std::end(ia)));
     }
     {
         const int ia[] = {1, 3, 5, 2, 4, 6, 7};
+        unary_counting_predicate<is_odd, int> pred((is_odd()));
         assert( std::is_partitioned(input_iterator<const int*>(std::begin(ia)),
                                     input_iterator<const int*>(std::begin(ia)),
-                                    is_odd()));
+                                    std::ref(pred)));
+        assert(pred.count() <= std::distance(std::begin(ia), std::begin(ia)));
+    }
+    {
+        const int ia[] = {1, 3, 5, 7, 9, 11, 2};
+        unary_counting_predicate<is_odd, int> pred((is_odd()));
+        assert( std::is_partitioned(input_iterator<const int*>(std::begin(ia)),
+                                    input_iterator<const int*>(std::end(ia)),
+                                    std::ref(pred)));
+        assert(pred.count() <= std::distance(std::begin(ia), std::end(ia)));
     }
 }