[Bug c++/19893] Synthetic pointers created from C++ references are broken

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=19893

--- Comment #11 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Martin Galvan
<martingalvan@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=3326303bf5ae4c92f2fbbff387ce231a16c1c8bf

commit 3326303bf5ae4c92f2fbbff387ce231a16c1c8bf
Author: Martin Galvan <martin.galvan@tallertechnologies.com>
Date:   Tue May 31 15:54:01 2016 -0300

    [PR gdb/19893] Fix handling of synthetic C++ references

    https://sourceware.org/bugzilla/show_bug.cgi?id=19893

    I've traced the main source of the problem to pieced_value_funcs.coerce_ref
not being
    implemented. Since gdb always assumes references are implemented as
pointers, this
    causes it to think that it's dealing with a NULL pointer, thus breaking any
operations
    involving synthetic references.

    What I did here was implementing pieced_value_funcs.coerce_ref using some
of the synthetic
    pointer handling code from indirect_pieced_value, as Pedro suggested. I
also made a few
    adjustments to the reference printing code so that it correctly shows
either the address
    of the referenced value or (if it's non-addressable) the "<synthetic
pointer>" string.

    I also wrote some unit tests based on Dwarf::assemble; these took a while
to make
    because in most cases I needed a synthetic reference to a physical
variable. Additionally,
    I started working on a unit test for classes that have a vtable, but ran
into a few issues
    so that'll probably go in a future patch. One thing that should definitely
be fixed is that
    proc function_range (called for MACRO_AT_func) will always try to
compile/link using gcc
    with the default options instead of g++, thus breaking C++ compilations
that require e.g. libstdc++.

    gdb/ChangeLog:

        * dwarf2loc.c (coerce_pieced_ref, indirect_synthetic_pointer,
        fetch_const_value_from_synthetic_pointer): New functions.
        (indirect_pieced_value): Move lower half to indirect_synthetic_pointer.
        (pieced_value_funcs): Implement coerce_ref.
        * valops.c (value_addr): Call coerce_ref for synthetic references.
        * valprint.c (valprint_check_validity): Return true for synthetic
        references.  Also, don't show "<synthetic pointer>" if they reference
        addressable values.
        (generic_val_print_ref): Handle synthetic references.  Also move some
        code to print_ref_address.
        (print_ref_address, get_value_addr_contents): New functions.

    gdb/testsuite/ChangeLog:

        * gdb.dwarf2/implref.exp: Rename to...
        * gdb.dwarf2/implref-const.exp: ...this.  Also add more test
statements.
        * gdb.dwarf2/implref-array.c: New file.
        * gdb.dwarf2/implref-array.exp: Likewise.
        * gdb.dwarf2/implref-global.c: Likewise.
        * gdb.dwarf2/implref-global.exp: Likewise.
        * gdb.dwarf2/implref-struct.c: Likewise.
        * gdb.dwarf2/implref-struct.exp: Likewise.

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