[Bug c++/65072] New: Segfault when parsing dectlype in trailing return type

[Bug c++/65072] New: Segfault when parsing dectlype in trailing return type

[uroc327 at cssbook dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65072

            Bug ID: 65072
           Summary: Segfault when parsing dectlype in trailing return type
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: uroc327 at cssbook dot de

[Bug c++/65072] Segfault when parsing dectlype in trailing return type

[uroc327 at cssbook dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65072

uroc327 at cssbook dot de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |uroc327 at cssbook dot de

--- Comment #1 from uroc327 at cssbook dot de ---
Created attachment 34769
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34769&action=edit
preprocessed output + stdout/stderr (first upload didn't seem to work?)

[Bug c++/65072] Segfault when parsing dectlype in trailing return type

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65072

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-valid-code
             Status|NEW                         |ASSIGNED
                 CC|                            |mpolacek at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org
   Target Milestone|---                         |4.8.5

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Let me look into this.

[Bug c++/65072] Segfault when parsing dectlype in trailing return type

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65072

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I couldn't bisect this, but started before r193621.

A bit more reduced:
template <typename> class C
{
  struct
  {
    int i;
  };
  auto operator*(const C m) -> C <decltype (m.i)>;
};
void fn1 (const C<float>);
C<float> a;

[Bug c++/65072] Segfault when parsing dectlype in trailing return type

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65072

--- Comment #5 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
EDG rejects it:

tes2.ii(7): error: incomplete type is not allowed
    auto operator*(const C m) -> C <decltype (m.i)>;
                                              ^

[Bug c++/65072] Segfault when parsing dectlype in trailing return type

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65072

--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
And clang accepts it.

It looks like we don't need the C<> around decltype:

template <typename> class C
{
  struct
  {
    int i;
  };
  auto operator*(const C m) -> decltype (m.i);
};
void fn1 (const C<float>);
C<float> a;

This one is accepted by clang, gcc 5/4.9/4.8 ICE.

[Bug c++/65072] Segfault when parsing dectlype in trailing return type

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65072

--- Comment #8 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(Just bailing out of build_class_member_access_expr if MEMBER is null fixes the
ICE, but in view of the unclarity above I don't think it's the right fix.)

[Bug c++/65072] Segfault when parsing dectlype in trailing return type

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65072

--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Here, we SEGV in build_class_member_access_expr, called recursively:

          tree anonymous_union;

          anonymous_union = lookup_anon_field (TREE_TYPE (object),
                                               DECL_CONTEXT (member));
          object = build_class_member_access_expr (object,
                                                   anonymous_union, [...]

anonymous_union is NULL and build_class_member_access_expr is not prepared to
handle that.  anonymous_union is NULL because lookup_anon_field returned NULL:
it tried to look for a "struct ._0" type in "const struct C" -- and found
nothing.  That is because "const struct C" doesn't have any fields!  But if I
change the testcase so that C is not const, it passes, because "struct C" then
has fields and lookup_anon_field is able to find a FIELD_DECL.

So the question is why "const struct C" doesn't have any fields.  I couldn't
figure that out yet :(.

[Bug c++/65072] Segfault when parsing dectlype in trailing return type

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65072

--- Comment #9 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Likely started with r151360 -- which doesn't reveal much, this rev was a part
of LTO merge, dealing with gimplification of types and symbols.

[Bug c++/65072] Segfault when parsing dectlype in trailing return type

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65072

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

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

--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Marek Polacek from comment #9)
> Likely started with r151360 -- which doesn't reveal much, this rev was a
> part of LTO merge, dealing with gimplification of types and symbols.

Actually, sorry for the error, it really started with r151529.

[Bug c++/65072] Segfault when parsing dectlype in trailing return type

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65072

--- Comment #11 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #10)
> Actually, sorry for the error, it really started with r151529.

Thanks -- I think I have a fix now.

[Bug c++/65072] Segfault when parsing dectlype in trailing return type

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65072

--- Comment #12 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Author: mpolacek
Date: Fri Mar 20 14:56:53 2015
New Revision: 221535

URL: https://gcc.gnu.org/viewcvs?rev=221535&root=gcc&view=rev
Log:
    PR c++/65072
    * typeck.c (lookup_anon_field): Make sure we're dealing with the main
    variant.

    * g++.dg/cpp0x/pr65072.C: New test.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/pr65072.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/typeck.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/65072] Segfault when parsing dectlype in trailing return type

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65072

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #13 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed.