[Bug c++/84642] [6/7/8 Regression] ICE: segfault reading through NULL current_template_parms in synthesize_implicit_template_parm

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84642

David Malcolm <dmalcolm at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-invalid-code
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2018-03-01
                 CC|                            |dmalcolm at gcc dot gnu.org
   Target Milestone|---                         |6.5
            Summary|internal compiler error:    |[6/7/8 Regression] ICE:
                   |Segmentation fault          |segfault reading through
                   |(tree_check()/synthesize_im |NULL current_template_parms
                   |plicit_template_parm())     |in
                   |                            |synthesize_implicit_templat
                   |                            |e_parm
     Ever confirmed|0                           |1

--- Comment #1 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Confirmed on trunk, 7, and 6 (and 5, with -std=c++14).

Started with r208426.

Segfault reading through NULL for "current_template_parms":

#1  0x0000000000a19850 in synthesize_implicit_template_parm
(parser=0x7ffff7ffbbd0, constr=<tree 0x0>)
    at ../../src/gcc/cp/parser.c:39078
39078         tree& new_parms = INNERMOST_TEMPLATE_PARMS
(current_template_parms);

(gdb) p scope_chain->template_parms 
$8 = <tree 0x0>