From: Jonathan Wakely <jwakely@redhat.com>
Date: Mon, 14 Jun 2021 21:42:05 +0000 (+0100)
Subject: libstdc++: Fix noexcept-specifier for ranges::empty
X-Git-Tag: releases/gcc-10.4.0~294
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=01c72ccad94e4f7b71504e502cba43d62b658143;p=thirdparty%2Fgcc.git

libstdc++: Fix noexcept-specifier for ranges::empty

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	* include/bits/range_access.h (ranges::empty): Check whether
	conversion to bool can throw.
	* testsuite/std/ranges/access/empty.cc: Check for correct
	noexcept-specifier.

(cherry picked from commit f9598d89a9f5a327ecdfa6f6978a0cfbe4447111)
---

diff --git a/libstdc++-v3/include/bits/range_access.h b/libstdc++-v3/include/bits/range_access.h
index 36bc55e6559a..aee72c3fae40 100644
--- a/libstdc++-v3/include/bits/range_access.h
+++ b/libstdc++-v3/include/bits/range_access.h
@@ -773,7 +773,7 @@ namespace ranges
 	_S_noexcept()
 	{
 	  if constexpr (__member_empty<_Tp>)
-	    return noexcept(std::declval<_Tp>().empty());
+	    return noexcept(bool(std::declval<_Tp>().empty()));
 	  else if constexpr (__size0_empty<_Tp>)
 	    return noexcept(_Size{}(std::declval<_Tp>()) == 0);
 	  else
diff --git a/libstdc++-v3/testsuite/std/ranges/access/empty.cc b/libstdc++-v3/testsuite/std/ranges/access/empty.cc
index 4b54ed7b3678..47dfca6513f9 100644
--- a/libstdc++-v3/testsuite/std/ranges/access/empty.cc
+++ b/libstdc++-v3/testsuite/std/ranges/access/empty.cc
@@ -68,9 +68,40 @@ test02()
   VERIFY( !std::ranges::empty(so) );
 }
 
+void
+test04()
+{
+  struct E1
+  {
+    bool empty() const noexcept { return {}; }
+  };
+
+  static_assert( noexcept(std::ranges::empty(E1{})) );
+
+  struct E2
+  {
+    bool empty() const noexcept(false) { return {}; }
+  };
+
+  static_assert( ! noexcept(std::ranges::empty(E2{})) );
+
+  struct E3
+  {
+    struct B
+    {
+      explicit operator bool() const noexcept(false) { return true; }
+    };
+
+    B empty() const noexcept { return {}; }
+  };
+
+  static_assert( ! noexcept(std::ranges::empty(E3{})) );
+}
+
 int
 main()
 {
   test01();
   test02();
+  test04();
 }