[gcc r12-5644] libstdc++: Fix fully-dynamic-string build

[gcc r12-5644] libstdc++: Fix fully-dynamic-string build

[Jonathan Wakely]

https://gcc.gnu.org/g:675afa21244d58640876da3287d303e376a3b59a

commit r12-5644-g675afa21244d58640876da3287d303e376a3b59a
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Nov 30 12:54:10 2021 +0000

    libstdc++: Fix fully-dynamic-string build
    
    My last change to the fully-dynamic-string actually broke it. This fixes
    the move constructor so it builds, and simplifies it slightly so that
    more code is common between the fully-dynamic enabled/disabled cases.
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/cow_string.h (basic_string(basic_string&&)): Fix
            mem-initializer for _GLIBCXX_FULLY_DYNAMIC_STRING==0 case.
            * testsuite/21_strings/basic_string/cons/char/noexcept_move_construct.cc:
            Remove outdated comment.
            * testsuite/21_strings/basic_string/cons/wchar_t/noexcept_move_construct.cc:
            Likewise.

Diff:
---
 libstdc++-v3/include/bits/cow_string.h                            | 8 +++-----
 .../21_strings/basic_string/cons/char/noexcept_move_construct.cc  | 1 -
 .../basic_string/cons/wchar_t/noexcept_move_construct.cc          | 1 -
 3 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/libstdc++-v3/include/bits/cow_string.h b/libstdc++-v3/include/bits/cow_string.h
index bafca7bb313..ced395b80b8 100644
--- a/libstdc++-v3/include/bits/cow_string.h
+++ b/libstdc++-v3/include/bits/cow_string.h
@@ -621,14 +621,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        *  @a __str is a valid, but unspecified string.
        */
       basic_string(basic_string&& __str) noexcept
-#if _GLIBCXX_FULLY_DYNAMIC_STRING == 0
       : _M_dataplus(std::move(__str._M_dataplus))
       {
+#if _GLIBCXX_FULLY_DYNAMIC_STRING == 0
+	// Make __str use the shared empty string rep.
 	__str._M_data(_S_empty_rep()._M_refdata());
-      }
 #else
-      : _M_dataplus(__str._M_rep())
-      {
 	// Rather than allocate an empty string for the rvalue string,
 	// just share ownership with it by incrementing the reference count.
 	// If the rvalue string was "leaked" then it was the unique owner,
@@ -637,8 +635,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  __gnu_cxx::__atomic_add_dispatch(&_M_rep()->_M_refcount, 2);
 	else
 	  __gnu_cxx::__atomic_add_dispatch(&_M_rep()->_M_refcount, 1);
-      }
 #endif
+      }
 
       /**
        *  @brief  Construct string from an initializer %list.
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/noexcept_move_construct.cc b/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/noexcept_move_construct.cc
index f04a491370d..74b0ed3910c 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/noexcept_move_construct.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/noexcept_move_construct.cc
@@ -23,7 +23,6 @@
 
 typedef std::string stype;
 
-// True except for COW strings with _GLIBCXX_FULLY_DYNAMIC_STRING:
 static_assert(std::is_nothrow_move_constructible<stype>::value, "Error");
 
 // True for std::allocator because is_always_equal, but not true in general:
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/cons/wchar_t/noexcept_move_construct.cc b/libstdc++-v3/testsuite/21_strings/basic_string/cons/wchar_t/noexcept_move_construct.cc
index d5dbf561ec0..53cb81d8aee 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/cons/wchar_t/noexcept_move_construct.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/cons/wchar_t/noexcept_move_construct.cc
@@ -23,7 +23,6 @@
 
 typedef std::wstring wstype;
 
-// True except for COW strings with _GLIBCXX_FULLY_DYNAMIC_STRING:
 static_assert(std::is_nothrow_move_constructible<wstype>::value, "Error");
 
 // True for std::allocator because is_always_equal, but not true in general: