[Bug c++/67343] New: C++ mangler does not follow ABI for local names in expressions

[Bug c++/67343] New: C++ mangler does not follow ABI for local names in expressions

[ian at airs dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67343

            Bug ID: 67343
           Summary: C++ mangler does not follow ABI for local names in
                    expressions
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ian at airs dot com
                CC: jason at gcc dot gnu.org
  Target Milestone: ---

If I compile this C++ file with current mainline

template<bool B> class H {
 public:
  enum T { V = B };
};

template <typename T> class C {
 public:
  enum { B1 = true, B2 = false };
};

template<typename T>
void f(typename H<C<T>::B1 && !C<T>::B2>::T) {}

void g() {
  f<int>(H<true>::V);
}

I get this symbol:

_Z1fIiEvN1HIXaasr1CIT_E2B1ntsrS3_2B2EE1TE

I believe that this symbol is not mangled according to the current C++ mangling
ABI.  The relevant part is the expression Xaasr1CIT_E2B1ntsrS3_2B2E,
specifically the local name sr1CIT_E2B1.  The mangling ABI says

<unresolved-name> ::= [gs] <base-unresolved-name>
                  ::= sr <unresolved-type> <base-unresolved-name>
                  ::= srN <unresolved-type> <unresolved-qualifier-level>+ E
<base-unresolved-name>
                  ::= [gs] sr <unresolved-qualifier-level>+ E
<base-unresolved-name>


<unresolved-type> ::= <template-param>
                  ::= <decltype>
                  ::= <substitution>

The string after "sr" is 1CIT_E2B1.  The 1C is not a template-param, a
decltype, or a substitution.  Therefore we must be using the fourth expansion
of <unresolved-name>, where we expect to see a series of
<unresolved-qualifier-level> entries, followed by an E, followed by a
<base-unresolved-name>.  But in fact what we see here is <type>
<unqualified-name>.  This is what the code in cp/mangle.c outputs:

          write_string ("sr");
          write_type (scope);
          write_member_name (member);

Either the mangling ABI or GCC itself is wrong.

[Bug c++/67343] C++ mangler does not follow ABI for local names in expressions

[ian at airs dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67343

--- Comment #1 from Ian Lance Taylor <ian at airs dot com> ---
For the record, when the same file is compiled with clang, the symbol is
_Z1fIiEvN1HIXaasr1CIT_EE2B1ntsr1CIS1_EE2B2EE1TE .  This symbol does appear to
follow the current API.  The relevant part of the expression here is
sr1CIT_EE2B1 .

[Bug c++/67343] C++ mangler does not follow ABI for local names in expressions

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67343

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |guilherme at amadio dot org

--- Comment #3 from Jason Merrill <jason at gcc dot gnu.org> ---
*** Bug 85648 has been marked as a duplicate of this bug. ***

[Bug c++/67343] C++ mangler does not follow ABI for local names in expressions

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67343

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2020-08-29
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1

[Bug c++/67343] C++ mangler does not follow ABI for local names in expressions

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67343

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |brennan at umanwizard dot com

--- Comment #4 from Jason Merrill <jason at gcc dot gnu.org> ---
*** Bug 88413 has been marked as a duplicate of this bug. ***

[Bug c++/67343] C++ mangler does not follow ABI for local names in expressions

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67343

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at gcc dot gnu.org

--- Comment #5 from Jason Merrill <jason at gcc dot gnu.org> ---
*** Bug 89818 has been marked as a duplicate of this bug. ***

[Bug c++/67343] C++ mangler does not follow ABI for local names in expressions

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67343

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:58fb912c15175f4444144b8a4ab52a4880b84994

commit r11-6300-g58fb912c15175f4444144b8a4ab52a4880b84994
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Dec 21 17:36:25 2020 -0500

    c++: Fix demangling of <unresolved-name>

    The ABI for unresolved scoped names on the RHS of . and -> used to be

      sr <type> <unqualified-id>

    That changed years ago to something more complex, but G++ was never
updated.
    This change was particularly incompatible for simple qualified-ids like
    A::x, which were previously mangled as sr1A1x, and now sr1AE1x.

    This obviously makes life hard for demanglers, which can't know whether to
    consume that E or not.  To work around this, we now try demangling with the
    newer ABI, and if that fails and we saw an "sr", try again with the older
    ABI.

    libiberty/ChangeLog:

            PR c++/67343
            * cp-demangle.h (struct d_info): Add unresolved_name_state.
            * cp-demangle.c (d_prefix): Add subst parm.
            (d_nested_name): Pass it.
            (d_unresolved_name): Split out from...
            (d_expression_1): ...here.
            (d_demangle_callback): Maybe retry with old sr mangling.
            * testsuite/demangle-expected: Add test.

[Bug c++/67343] C++ mangler does not follow ABI for unresolved names in expressions

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67343

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> ---
Created attachment 49828
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49828&action=edit
WIP Fix

Here's my current patch for this bug, but I think I'm going to hold off on it
pending the resolution of ABI issue 38.

[Bug c++/67343] C++ mangler does not follow ABI for unresolved names in expressions

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67343

--- Comment #8 from Jason Merrill <jason at gcc dot gnu.org> ---
Created attachment 49829
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49829&action=edit
Follow-on patch

And this one fixes ->:: according to the current ABI, but also holding for the
issue resolution.

[Bug c++/67343] C++ mangler does not follow ABI for unresolved names in expressions

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67343

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |yedeng.yd at linux dot alibaba.com

--- Comment #9 from Jason Merrill <jason at gcc dot gnu.org> ---
*** Bug 109887 has been marked as a duplicate of this bug. ***