gdb: BigPtrArrayPrinter gets confused by libstdc++ std::unique_ptr

It looks like this in libstdc++:

<BigPtrArray> = {
m_ppInf = {
_M_t = {
<std::__uniq_ptr_impl<BlockInfo*, std::default_delete<BlockInfo* []> >> = {
_M_t = {
<std::_Tuple_impl<0, BlockInfo**, std::default_delete<BlockInfo* []> >> = {
<std::_Tuple_impl<1, std::default_delete<BlockInfo* []> >> = {
<std::_Head_base<1, std::default_delete<BlockInfo* []>, true>> = {
_M_head_impl = {<No data fields>}
}, <No data fields>},
<std::_Head_base<0, BlockInfo**, false>> = {
_M_head_impl = 0x567fd20
}, <No data fields>}, <No data fields>}
}, <No data fields>}
},

Note there are 2 _M_head_impl members, and somehow gdb 11.1-2.fc34 picks
the wrong one.

A manual cast to std::_Head_base<0, BlockInfo**, false> seems to help.

Change-Id: I1332c2fc6eb2661d417fd92a73aed977bbb1dcea
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/126220
Tested-by: Jenkins
Reviewed-by: Michael Stahl <michael.stahl@allotropia.de>
(cherry picked from commit c9267ca4fa7fa94a1bf79320bec54428a6ad4804)

1 files changed, 5 insertions, 1 deletions

diff --git a/solenv/gdb/libreoffice/sw.py b/solenv/gdb/libreoffice/sw.py
index e170709fb79c..7a5ce193684b 100644
--- a/solenv/gdb/libreoffice/sw.py
+++ b/solenv/gdb/libreoffice/sw.py
@@ -8,6 +8,7 @@
 #
 
 import six
+import gdb
 from libreoffice.util import printing
 
 class SwPositionPrinter(object):
@@ -194,7 +195,10 @@ class BigPtrArrayPrinter(object):
     class _iterator(six.Iterator):
 
         def __init__(self, array):
-            self.blocks = array['m_ppInf']['_M_t']['_M_t']['_M_head_impl']
+            # libstdc++ unique_ptr is a std::tuple which contains multiple
+            # _M_head_impl members and gdb may pick the wrong one by default
+            # so have to manually cast it to the one that contains the array
+            self.blocks = array['m_ppInf']['_M_t']['_M_t'].cast(gdb.lookup_type("std::_Head_base<0, BlockInfo**, false>"))['_M_head_impl']
             self.count = array['m_nSize']
             self.pos = 0
             self.block_count = array['m_nBlock']