Created attachment 7662 [details]
preprocessed input from sample program, file mini.ii

When running gdb on a program using an instance of the unique_ptr class template, the identifier 'tuple' can no longer be accessed in any way, as otherwise valid expressions now give a syntax error. A minimal example:

mini.cpp:

    #include <memory>

    int main()
    {
      std::unique_ptr<int> p;
    }

compile this with gcc (version 4.8.1) using the command

    g++ -std=c++11 -ggdb -o mini mini.cpp

now run gdb and ask to print the (nonexistent) variable 'tuple'

    $ gdb mini
    GNU gdb (GDB) 7.6.1-ubuntu
    Copyright (C) 2013 Free Software Foundation, Inc.
    License GPLv3+: GNU GPL version 3 or later <http://gnu.org/license/gpl.html>
    This is free software: you are free to change and redistribute it.
    There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
    and "show warranty" for details.
    This GDB was configured as "x86_64-linux-gnu".
    For bug reporting instructions, please see:
    <http://www.gnu.org/software/gdb/bugs/>...
    Reading symbols from /home/marc/atlas/sources/stand-alone/mini...done.
    (gdb) p tuple
    A syntax error in expression, near `'.
    (gdb) 

Whereas in a program not using any unique_ptr (for instance the above program after removing the unique statement in 'main') one would correctly get

    (gdb) p tuple
    No symbol "tuple" in current context.

It seems that 'tuple' has changed its syntax category for gdb, making any access to variables/fields called 'tuple' impossible. I stumbled on this when debugging a program that actually used a field of that name, but the bug does not appear to depend on that circumstance.


Looking and the (attached) preprocessed input, it seems that the problem might be that 'tuple' is defined as a variadic template class:

    template<typename...>
      class tuple;

and later

    template<typename... _Elements>
      class tuple : public _Tuple_impl<0, _Elements...>
      { ... };