[gcc r12-178] libstdc++: Fix various bugs in ranges_algo.h [PR100187, ...]

[Patrick Palka]

https://gcc.gnu.org/g:d91e7eab3a2c3957c2220ad71e62d9fc78cccb9b

commit r12-178-gd91e7eab3a2c3957c2220ad71e62d9fc78cccb9b
Author: Patrick Palka <ppalka@redhat.com>
Date:   Tue Apr 27 23:21:19 2021 -0400

    libstdc++: Fix various bugs in ranges_algo.h [PR100187, ...]
    
    This fixes some bugs with our ranges algorithms in uncommon situations,
    such as when the return type of a predicate is a non-copyable class type
    that's implicitly convertible to bool (PR100187), when a comparison
    predicate isn't invocable as an rvalue (PR100237), and when the return
    type of a projection function is non-copyable (PR100249).
    
    This also fixes PR100287, which reports that we're moving __first twice
    when constructing with it an empty subrange in ranges::partition.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/100187
            PR libstdc++/100237
            PR libstdc++/100249
            PR libstdc++/100287
            * include/bits/ranges_algo.h (__search_n_fn::operator()): Give
            the __value_comp lambda an explicit bool return type.
            (__is_permutation_fn::operator()): Give the __proj_scan local
            variable auto&& return type.  Give the __comp_scan lambda an
            explicit bool return type.
            (__remove_fn::operator()): Give the __pred lambda an explicit
            bool return type.
            (__partition_fn::operator()): Don't std::move __first twice
            when returning an empty subrange.
            (__min_fn::operator()): Don't std::move __comp.
            (__max_fn::operator()): Likewise.
            (__minmax_fn::operator()): Likewise.

Diff:
---
 libstdc++-v3/include/bits/ranges_algo.h | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/libstdc++-v3/include/bits/ranges_algo.h b/libstdc++-v3/include/bits/ranges_algo.h
index 23e6480b9a8..cda3042c11f 100644
--- a/libstdc++-v3/include/bits/ranges_algo.h
+++ b/libstdc++-v3/include/bits/ranges_algo.h
@@ -562,7 +562,7 @@ namespace ranges
 	if (__count <= 0)
 	  return {__first, __first};
 
-	auto __value_comp = [&] <typename _Rp> (_Rp&& __arg) {
+	auto __value_comp = [&] <typename _Rp> (_Rp&& __arg) -> bool {
 	    return std::__invoke(__pred, std::forward<_Rp>(__arg), __value);
 	};
 	if (__count == 1)
@@ -805,8 +805,8 @@ namespace ranges
 
 	for (auto __scan = __first1; __scan != __last1; ++__scan)
 	  {
-	    auto __proj_scan = std::__invoke(__proj1, *__scan);
-	    auto __comp_scan = [&] <typename _Tp> (_Tp&& __arg) {
+	    auto&& __proj_scan = std::__invoke(__proj1, *__scan);
+	    auto __comp_scan = [&] <typename _Tp> (_Tp&& __arg) -> bool {
 	      return std::__invoke(__pred, __proj_scan,
 				   std::forward<_Tp>(__arg));
 	    };
@@ -1256,7 +1256,7 @@ namespace ranges
       operator()(_Iter __first, _Sent __last,
 		 const _Tp& __value, _Proj __proj = {}) const
       {
-	auto __pred = [&] (auto&& __arg) {
+	auto __pred = [&] (auto&& __arg) -> bool {
 	  return std::forward<decltype(__arg)>(__arg) == __value;
 	};
 	return ranges::remove_if(__first, __last,
@@ -2537,11 +2537,11 @@ namespace ranges
 	else
 	  {
 	    if (__first == __last)
-	      return {std::move(__first), std::move(__first)};
+	      return {__first, __first};
 
 	    while (std::__invoke(__pred, std::__invoke(__proj, *__first)))
 	      if (++__first == __last)
-		return {std::move(__first), std::move(__first)};
+		return {__first, __first};
 
 	    auto __next = __first;
 	    while (++__next != __last)
@@ -3118,7 +3118,7 @@ namespace ranges
       operator()(const _Tp& __a, const _Tp& __b,
 		 _Comp __comp = {}, _Proj __proj = {}) const
       {
-	if (std::__invoke(std::move(__comp),
+	if (std::__invoke(__comp,
 			  std::__invoke(__proj, __b),
 			  std::__invoke(__proj, __a)))
 	  return __b;
@@ -3172,7 +3172,7 @@ namespace ranges
       operator()(const _Tp& __a, const _Tp& __b,
 		 _Comp __comp = {}, _Proj __proj = {}) const
       {
-	if (std::__invoke(std::move(__comp),
+	if (std::__invoke(__comp,
 			  std::__invoke(__proj, __a),
 			  std::__invoke(__proj, __b)))
 	  return __b;
@@ -3272,7 +3272,7 @@ namespace ranges
       operator()(const _Tp& __a, const _Tp& __b,
 		 _Comp __comp = {}, _Proj __proj = {}) const
       {
-	if (std::__invoke(std::move(__comp),
+	if (std::__invoke(__comp,
 			  std::__invoke(__proj, __b),
 			  std::__invoke(__proj, __a)))
 	  return {__b, __a};