[libcxx-commits] [PATCH] D70873: [LIBC++]std::reduce(begin, end, init) does not accept init with only move constructor

[kamlesh kumar via Phabricator via libcxx-commits]

kamleshbhalui created this revision.
kamleshbhalui added reviewers: mclow.lists, ldionne.
kamleshbhalui added a project: libc++.
Herald added subscribers: dexonsmith, christof.

As per the c++ when the user-declare move-constructor compiler deletes the copy constructor.
so modified the  std::reduce(begin, end, init) so it does not require copy constructor and behavior matches with 
std::reduce(begin, end, init,op).

It fixes this https://bugs.llvm.org/show_bug.cgi?id=43013


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D70873

Files:
  libcxx/include/numeric
  libcxx/test/std/numerics/numeric.ops/reduce/reduce_init.pass.cpp


Index: libcxx/test/std/numerics/numeric.ops/reduce/reduce_init.pass.cpp
===================================================================
--- libcxx/test/std/numerics/numeric.ops/reduce/reduce_init.pass.cpp
+++ libcxx/test/std/numerics/numeric.ops/reduce/reduce_init.pass.cpp
@@ -65,5 +65,16 @@
     test<random_access_iterator<const int*> >();
     test<const int*>();
 
+    //test for checking std::reduce should not require copy constructor for initial object
+    {
+    struct T {
+     T(int){}
+     T(T &&){}
+     T &operator=(T &&){}
+     T operator+(const T &) const{}
+    };
+    T t[1]{1};
+    std::reduce(t, t + 1, T(0));
+    }
   return 0;
 }
Index: libcxx/include/numeric
===================================================================
--- libcxx/include/numeric
+++ libcxx/include/numeric
@@ -193,7 +193,9 @@
 _Tp
 reduce(_InputIterator __first, _InputIterator __last, _Tp __init)
 {
-    return _VSTD::reduce(__first, __last, __init, _VSTD::plus<>());
+    for (; __first != __last; ++__first)
+        __init = _VSTD::plus<>()(__init, *__first);
+    return __init;
 }
 
 template <class _InputIterator>


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