Re: [PATCH] LWG 2899 - Make is_move_constructible correct for unique_ptr

[Jonathan Wakely <jwakely at redhat dot com>]

On 14/05/19 12:17 +0100, Jonathan Wakely wrote:
> 	* include/bits/unique_ptr.h (__uniq_ptr_impl): Add move constructor,
> 	move assignment operator.
> 	(__uniq_ptr_impl::release(), __uniq_ptr_impl::reset(pointer)): Add.
> 	(__uniq_ptr_data): New class template with conditionally deleted
> 	special members.
> 	(unique_ptr, unique_ptr<T[], D>): Change type of data member from
> 	__uniq_ptr_impl<T, D> to __uniq_ptr_data<T, D>. Define move
> 	constructor and move assignment operator as defaulted.
> 	(unique_ptr::release(), unique_ptr<T[], D>::release()): Forward to
> 	__uniq_ptr_impl::release().
> 	(unique_ptr::reset(pointer), unique_ptr<T[], D>::reset<U>(U)): Forward
> 	to __uniq_ptr_impl::reset(pointer).
> 	* python/libstdcxx/v6/printers.py (UniquePointerPrinter.__init__):
> 	Check for new __uniq_ptr_data type.
> 	* testsuite/20_util/unique_ptr/dr2899.cc: New test.

This updates the Xmethod for the new base class.

Tested x86_64-linux, committed to trunk.

commit 5b013bcaeae51850ced6eaff0c6626915565c88a
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Sat May 18 00:05:47 2019 +0100

    PR libstdc++/90520 adjust Xmethod for recent unique_ptr changes
    
            PR libstdc++/90520
            * python/libstdcxx/v6/printers.py (UniquePointerPrinter.__init__):
            Raise exception if unique_ptr tuple member has unknown structure.
            * python/libstdcxx/v6/xmethods.py (UniquePtrGetWorker.__call__):
            Adjust worker to support new __uniq_ptr_data base class. Do not
            assume field called _M_head_impl is the first tuple element.

diff --git a/libstdc++-v3/python/libstdcxx/v6/printers.py b/libstdc++-v3/python/libstdcxx/v6/printers.py
index 162b00760e6..05143153bee 100644
--- a/libstdc++-v3/python/libstdcxx/v6/printers.py
+++ b/libstdc++-v3/python/libstdcxx/v6/printers.py
@@ -197,6 +197,8 @@ class UniquePointerPrinter:
             self.pointer = tuple_member['_M_head_impl']
         elif head_field.is_base_class:
             self.pointer = tuple_member.cast(head_field.type)
+        else:
+            raise ValueError("Unsupported implementation for tuple in unique_ptr: %s" % impl_type)
 
     def children (self):
         return SmartPtrIterator(self.pointer)
diff --git a/libstdc++-v3/python/libstdcxx/v6/xmethods.py b/libstdc++-v3/python/libstdcxx/v6/xmethods.py
index c405d8a25d5..623cb80bc0e 100644
--- a/libstdc++-v3/python/libstdcxx/v6/xmethods.py
+++ b/libstdc++-v3/python/libstdcxx/v6/xmethods.py
@@ -586,11 +586,22 @@ class UniquePtrGetWorker(gdb.xmethod.XMethodWorker):
 
     def __call__(self, obj):
         impl_type = obj.dereference().type.fields()[0].type.tag
-        if re.match('^std::(__\d+::)?__uniq_ptr_impl<.*>$', impl_type): # New implementation
-            return obj['_M_t']['_M_t']['_M_head_impl']
+        # Check for new implementations first:
+        if re.match('^std::(__\d+::)?__uniq_ptr_(data|impl)<.*>$', impl_type):
+            tuple_member = obj['_M_t']['_M_t']
         elif re.match('^std::(__\d+::)?tuple<.*>$', impl_type):
-            return obj['_M_t']['_M_head_impl']
-        return None
+            tuple_member = obj['_M_t']
+        else:
+            return None
+        tuple_impl_type = tuple_member.type.fields()[0].type # _Tuple_impl
+        tuple_head_type = tuple_impl_type.fields()[1].type   # _Head_base
+        head_field = tuple_head_type.fields()[0]
+        if head_field.name == '_M_head_impl':
+            return tuple_member['_M_head_impl']
+        elif head_field.is_base_class:
+            return tuple_member.cast(head_field.type)
+        else:
+            return None
 
 class UniquePtrDerefWorker(UniquePtrGetWorker):
     "Implements std::unique_ptr<T>::operator*()"