[Bug libstdc++/91997] pretty printers: The __node_type type alias in _Hashtable is not available

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91997

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Fri Nov 29 14:47:03 2019
New Revision: 278846

URL: https://gcc.gnu.org/viewcvs?rev=278846&root=gcc&view=rev
Log:
libstdc++:: improve how pretty printers find node types (PR 91997)

This fixes two related problems.

The iterators for node-based containers use nested typedefs such as
std::list<T>::iterator::_Node to denote their node types. As reported in
https://bugzilla.redhat.com/show_bug.cgi?id=1053438 those typedefs are
not always present in the debug info. That means the pretty printers
cannot find them using gdb.lookup_type (via the find_type helper).
Instead of looking up the nested typedefs this patch makes the printers
look up the actual class templates directly.

A related problem (and the original topic of PR 91997) is that GDB fails
to find types via gdb.lookup_type when printing a backtrace from a
non-C++ functiion: https://sourceware.org/bugzilla/show_bug.cgi?id=25234
That is also solved by not looking up the nested typedef.

        PR libstdc++/91997
        * python/libstdcxx/v6/printers.py (find_type): Fail more gracefully
        if we run out of base classes to look at.
        (llokup_templ_spec, lookup_node_type): New utilities to find node
        types for node-based containers.
        (StdListPrinter.children, NodeIteratorPrinter.__init__)
        (NodeIteratorPrinter.to_string, StdSlistPrinter.children)
        (StdSlistIteratorPrinter.to_string, StdRbtreeIteratorPrinter.__init__)
        (StdMapPrinter.children, StdSetPrinter.children)
        (StdForwardListPrinter.children): Use lookup_node_type instead of
        find_type.
        (StdListIteratorPrinter.__init__, StdFwdListIteratorPrinter.__init__):
        Pass name of node type to NodeIteratorPrinter constructor.
        (Tr1HashtableIterator.__init__): Rename argument.
        (StdHashtableIterator.__init__): Likewise. Use lookup_templ_spec
        instead of find_type.
        * testsuite/libstdc++-prettyprinters/59161.cc: Remove workaround for
        _Node typedef not being present in debuginfo.
        * testsuite/libstdc++-prettyprinters/91997.cc: New test.

Added:
    trunk/libstdc++-v3/testsuite/libstdc++-prettyprinters/91997.cc
Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/python/libstdcxx/v6/printers.py
    trunk/libstdc++-v3/testsuite/libstdc++-prettyprinters/59161.cc