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* [gcc r11-8847] libstdc++: Change [cmp.alg] assertions to constraints
@ 2021-08-11 15:42 Jonathan Wakely
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From: Jonathan Wakely @ 2021-08-11 15:42 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:2fbb6039c5fcc7b85b048eeb748bea4753ff99cc
commit r11-8847-g2fbb6039c5fcc7b85b048eeb748bea4753ff99cc
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Mon Jun 14 12:25:43 2021 +0100
libstdc++: Change [cmp.alg] assertions to constraints
This moves the same_as<decay_t<_Tp>, decay_t<_Up>> checks from the
[cmp.alg] function bodies into their constraints.
Also add a test for the compare_xxx_order_fallback algorithms.
libstdc++-v3/ChangeLog:
* libsupc++/compare (__decayed_same_as): New helper concept.
(strong_order, weak_order, partial_order): Constrain with new
concept instead of using static_assert.
(compare_strong_order_fallback, compare_weak_order_fallback)
(compare_partial_order_fallback): Likewise. Do not deduce return
types. Remove redundant if-constexpr checks.
* testsuite/18_support/comparisons/algorithms/fallback.cc: New test.
(cherry picked from commit e2c79b968ff95421c31a5a9a1b80b11321fe70d2)
Diff:
---
libstdc++-v3/libsupc++/compare | 39 ++++++++------------
.../18_support/comparisons/algorithms/fallback.cc | 42 ++++++++++++++++++++++
2 files changed, 57 insertions(+), 24 deletions(-)
diff --git a/libstdc++-v3/libsupc++/compare b/libstdc++-v3/libsupc++/compare
index 82d00889272..b1f342113f1 100644
--- a/libstdc++-v3/libsupc++/compare
+++ b/libstdc++-v3/libsupc++/compare
@@ -600,6 +600,9 @@ namespace std
// FIXME: || floating_point<remove_reference_t<_Tp>>
|| __cmp3way<strong_ordering, _Tp, _Up>;
+ template<typename _Tp, typename _Up>
+ concept __decayed_same_as = same_as<decay_t<_Tp>, decay_t<_Up>>;
+
class _Strong_order
{
template<typename _Tp, typename _Up>
@@ -620,14 +623,12 @@ namespace std
friend class _Strong_fallback;
public:
- template<typename _Tp, typename _Up>
+ template<typename _Tp, __decayed_same_as<_Tp> _Up>
requires __strongly_ordered<_Tp, _Up>
constexpr strong_ordering
operator()(_Tp&& __e, _Up&& __f) const
noexcept(_S_noexcept<_Tp, _Up>())
{
- static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
-
/* FIXME:
if constexpr (floating_point<decay_t<_Tp>>)
return __cmp_cust::__fp_strong_order(__e, __f);
@@ -669,14 +670,12 @@ namespace std
friend class _Weak_fallback;
public:
- template<typename _Tp, typename _Up>
+ template<typename _Tp, __decayed_same_as<_Tp> _Up>
requires __weakly_ordered<_Tp, _Up>
constexpr weak_ordering
operator()(_Tp&& __e, _Up&& __f) const
noexcept(_S_noexcept<_Tp, _Up>())
{
- static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
-
if constexpr (floating_point<decay_t<_Tp>>)
return __cmp_cust::__fp_weak_ordering(__e, __f);
else if constexpr (__adl_weak<_Tp, _Up>)
@@ -716,14 +715,12 @@ namespace std
friend class _Partial_fallback;
public:
- template<typename _Tp, typename _Up>
+ template<typename _Tp, __decayed_same_as<_Tp> _Up>
requires __partially_ordered<_Tp, _Up>
constexpr partial_ordering
operator()(_Tp&& __e, _Up&& __f) const
noexcept(_S_noexcept<_Tp, _Up>())
{
- static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
-
if constexpr (__adl_partial<_Tp, _Up>)
return partial_ordering(partial_order(static_cast<_Tp&&>(__e),
static_cast<_Up&&>(__f)));
@@ -759,18 +756,16 @@ namespace std
}
public:
- template<typename _Tp, typename _Up>
+ template<typename _Tp, __decayed_same_as<_Tp> _Up>
requires __strongly_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up>
- constexpr decltype(auto)
+ constexpr strong_ordering
operator()(_Tp&& __e, _Up&& __f) const
noexcept(_S_noexcept<_Tp, _Up>())
{
- static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
-
if constexpr (__strongly_ordered<_Tp, _Up>)
return _Strong_order{}(static_cast<_Tp&&>(__e),
static_cast<_Up&&>(__f));
- else if constexpr (__op_eq_lt<_Tp, _Up>)
+ else // __op_eq_lt<_Tp, _Up>
return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f)
? strong_ordering::equal
: static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f)
@@ -793,18 +788,16 @@ namespace std
}
public:
- template<typename _Tp, typename _Up>
+ template<typename _Tp, __decayed_same_as<_Tp> _Up>
requires __weakly_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up>
- constexpr decltype(auto)
+ constexpr weak_ordering
operator()(_Tp&& __e, _Up&& __f) const
noexcept(_S_noexcept<_Tp, _Up>())
{
- static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
-
if constexpr (__weakly_ordered<_Tp, _Up>)
return _Weak_order{}(static_cast<_Tp&&>(__e),
static_cast<_Up&&>(__f));
- else if constexpr (__op_eq_lt<_Tp, _Up>)
+ else // __op_eq_lt<_Tp, _Up>
return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f)
? weak_ordering::equivalent
: static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f)
@@ -827,18 +820,16 @@ namespace std
}
public:
- template<typename _Tp, typename _Up>
+ template<typename _Tp, __decayed_same_as<_Tp> _Up>
requires __partially_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up>
- constexpr decltype(auto)
+ constexpr partial_ordering
operator()(_Tp&& __e, _Up&& __f) const
noexcept(_S_noexcept<_Tp, _Up>())
{
- static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
-
if constexpr (__partially_ordered<_Tp, _Up>)
return _Partial_order{}(static_cast<_Tp&&>(__e),
static_cast<_Up&&>(__f));
- else if constexpr (__op_eq_lt<_Tp, _Up>)
+ else // __op_eq_lt<_Tp, _Up>
return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f)
? partial_ordering::equivalent
: static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f)
diff --git a/libstdc++-v3/testsuite/18_support/comparisons/algorithms/fallback.cc b/libstdc++-v3/testsuite/18_support/comparisons/algorithms/fallback.cc
new file mode 100644
index 00000000000..ae458528f17
--- /dev/null
+++ b/libstdc++-v3/testsuite/18_support/comparisons/algorithms/fallback.cc
@@ -0,0 +1,42 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do compile { target c++20 } }
+
+#include <compare>
+
+using std::strong_ordering;
+using std::partial_ordering;
+
+namespace adl
+{
+ struct S { };
+ void strong_ordering(const S&, const S&);
+ bool operator==(const S&, S&) { return true; }
+ bool operator<(const S&, S&) { return true; }
+}
+
+template<typename T, typename U>
+ concept has_strong_order_fallback = requires (T& t, U& u) {
+ std::compare_strong_order_fallback(t, u);
+ };
+
+template<typename T, typename U>
+ concept has_weak_order_fallback = requires (T& t, U& u) {
+ std::compare_weak_order_fallback(t, u);
+ };
+
+template<typename T, typename U>
+ concept has_partial_order_fallback = requires (T& t, U& u) {
+ std::compare_partial_order_fallback(t, u);
+ };
+
+using adl::S;
+
+static_assert( has_strong_order_fallback<S, S> );
+static_assert( has_strong_order_fallback<const S, S> );
+static_assert( ! has_strong_order_fallback<const S, const S> );
+static_assert( has_weak_order_fallback<S, S> );
+static_assert( has_weak_order_fallback<const S, S> );
+static_assert( ! has_weak_order_fallback<const S, const S> );
+static_assert( has_partial_order_fallback<S, S> );
+static_assert( has_partial_order_fallback<const S, S> );
+static_assert( ! has_partial_order_fallback<const S, const S> );
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