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.

diff --git a/libstdc++-v3/python/libstdcxx/v6/xmethods.py b/libstdc++-v3/python/libstdcxx/v6/xmethods.py
index 42e60eb57b1fe6f0be523f97bbffb734f16fe7f2..dcef285180a8dacf7358100a875116aff069bf43 100644 (file)
--- a/libstdc++-v3/python/libstdcxx/v6/xmethods.py
+++ b/libstdc++-v3/python/libstdcxx/v6/xmethods.py
@@ -193,11 +193,14 @@ 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 2d7e846334fc8fca514d938486695854156b888e..e4077c14ff5a18b9ba1170abbe45b15146489312 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
 }