libstdc++: Fix std::deque::size() Xmethod [PR112491]

The Xmethod for std::deque::size() assumed that the first element would
be at the start of the first node. That's only true if elements are only
added at the back. If an element is inserted at the front, or removed
from the front (or anywhere before the middle) then the first node will
not be completely populated, and the Xmethod will give the wrong result.

libstdc++-v3/ChangeLog:

	PR libstdc++/112491
	* python/libstdcxx/v6/xmethods.py (DequeWorkerBase.size): Fix
	calculation to use _M_start._M_cur.
	* testsuite/libstdc++-xmethods/deque.cc: Check failing cases.

(cherry picked from commit 4db820928065eccbeb725406450d826186582b9f)

diff --git a/libstdc++-v3/python/libstdcxx/v6/xmethods.py b/libstdc++-v3/python/libstdcxx/v6/xmethods.py
index d6cbcf139c5808d7aea0002f61fe693c5d396c32..5223cce76ca80c850b727e201011d38c5d83297f 100644 (file)
--- a/libstdc++-v3/python/libstdcxx/v6/xmethods.py
+++ b/libstdc++-v3/python/libstdcxx/v6/xmethods.py
@@ -168,11 +168,14 @@ class DequeWorkerBase(gdb.xmethod.XMethodWorker):
         self._bufsize = 512 // val_type.sizeof or 1
 
     def size(self, obj):
-        first_node = obj['_M_impl']['_M_start']['_M_node']
-        last_node = obj['_M_impl']['_M_finish']['_M_node']
-        cur = obj['_M_impl']['_M_finish']['_M_cur']
-        first = obj['_M_impl']['_M_finish']['_M_first']
-        return (last_node - first_node) * self._bufsize + (cur - first)
+        start = obj['_M_impl']['_M_start']
+        finish = obj['_M_impl']['_M_finish']
+        if not start['_M_node']:
+            return 0
+        return (self._bufsize
+                * (finish['_M_node'] - start['_M_node'] - 1)
+                + (finish['_M_cur'] - finish['_M_first'])
+                + (start['_M_last'] - start['_M_cur']))
 
     def index(self, obj, idx):
         first_node = obj['_M_impl']['_M_start']['_M_node']

diff --git a/libstdc++-v3/testsuite/libstdc++-xmethods/deque.cc b/libstdc++-v3/testsuite/libstdc++-xmethods/deque.cc
index b29e1a0abca078c4dd5e5807a84af42ef314b9b7..1dd0bd8d8755e632e00ce0caefd3ce8fc3838d93 100644 (file)
--- a/libstdc++-v3/testsuite/libstdc++-xmethods/deque.cc
+++ b/libstdc++-v3/testsuite/libstdc++-xmethods/deque.cc
@@ -67,6 +67,26 @@ main ()
 // { dg-final { whatis-test q1.back() int } }
 // { dg-final { whatis-test q3\[0\] int } }
 
+  // PR libstdc++/112491
+  std::deque<int> q5;
+  q5.push_front(0);
+// { dg-final { note-test q5.size() 1 } }
+  std::deque<int> q6 = q1;
+  q6.pop_front();
+// { dg-final { note-test {q6.size() == (q1_size-1)} true } }
+  std::deque<int> q7 = q2;
+  q7.pop_front();
+  q7.pop_front();
+// { dg-final { note-test {q7.size() == (q2_size-2)} true } }
+  std::deque<int> q8 = q3;
+  q8.pop_front();
+  q8.pop_front();
+  q8.pop_front();
+// { dg-final { note-test {q8.size() == (q3_size-3)} true } }
+  std::deque<int> q9 = q8;
+  q9.clear();
+// { dg-final { note-test q9.size() 0 } }
+
   return 0;  // Mark SPOT
 }