[Bug c++/71513] New: ICE on valid C++11 code (with alignas specifier) on x86_64-linux-gnu: Segmentation fault

["su at cs dot ucdavis.edu" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71513

            Bug ID: 71513
           Summary: ICE on valid C++11 code (with alignas specifier) on
                    x86_64-linux-gnu: Segmentation fault
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu
  Target Milestone: ---

The following C++11 code causes an ICE when compiled with the current GCC trunk
on x86_64-linux-gnu in both 32-bit and 64-bit modes.  

It also affects 6.1.x and is a regression from 5.4.x. 


$ g++-trunk -v
Using built-in specs.
COLLECT_GCC=g++-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/7.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-source-trunk/configure --enable-languages=c,c++,lto
--prefix=/usr/local/gcc-trunk --disable-bootstrap
Thread model: posix
gcc version 7.0.0 20160612 (experimental) [trunk revision 237336] (GCC)
$
$ g++-5.4 -std=c++11 -c small.cpp
$ clang++-3.8 -std=c++11 -c small.cpp
$
$ g++-trunk -std=c++11 -c small.cpp
small.cpp: In instantiation of âclass A<1, char>â:
small.cpp:7:15:   required from here
small.cpp:4:24: internal compiler error: Segmentation fault
   enum alignas (N) E : T;
                        ^
0xdb2b7f crash_signal
        ../../gcc-source-trunk/gcc/toplev.c:335
0x6fd083 contains_struct_check
        ../../gcc-source-trunk/gcc/tree.h:3143
0x6fd083 tsubst_attributes
        ../../gcc-source-trunk/gcc/cp/pt.c:9669
0x6fd083 lookup_template_class_1
        ../../gcc-source-trunk/gcc/cp/pt.c:8425
0x6fd083 lookup_template_class(tree_node*, tree_node*, tree_node*, tree_node*,
int, int)
        ../../gcc-source-trunk/gcc/cp/pt.c:8654
0x6feb0b tsubst_aggr_type
        ../../gcc-source-trunk/gcc/cp/pt.c:11437
0x6e7df7 tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../gcc-source-trunk/gcc/cp/pt.c:12908
0x6f0425 tsubst_decl
        ../../gcc-source-trunk/gcc/cp/pt.c:12229
0x6e81fe tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../gcc-source-trunk/gcc/cp/pt.c:12829
0x71bb64 instantiate_class_template_1
        ../../gcc-source-trunk/gcc/cp/pt.c:10091
0x71bb64 instantiate_class_template(tree_node*)
        ../../gcc-source-trunk/gcc/cp/pt.c:10372
0x7be313 complete_type(tree_node*)
        ../../gcc-source-trunk/gcc/cp/typeck.c:132
0x683ee8 start_decl_1(tree_node*, bool)
        ../../gcc-source-trunk/gcc/cp/decl.c:5070
0x6aacad start_decl(cp_declarator const*, cp_decl_specifier_seq*, int,
tree_node*, tree_node*, tree_node**)
        ../../gcc-source-trunk/gcc/cp/decl.c:5033
0x7aa4b2 cp_parser_init_declarator
        ../../gcc-source-trunk/gcc/cp/parser.c:18566
0x7ab009 cp_parser_simple_declaration
        ../../gcc-source-trunk/gcc/cp/parser.c:12378
0x7ab311 cp_parser_block_declaration
        ../../gcc-source-trunk/gcc/cp/parser.c:12246
0x7b46f0 cp_parser_declaration
        ../../gcc-source-trunk/gcc/cp/parser.c:12143
0x7b31c4 cp_parser_declaration_seq_opt
        ../../gcc-source-trunk/gcc/cp/parser.c:12022
0x7b34f8 cp_parser_translation_unit
        ../../gcc-source-trunk/gcc/cp/parser.c:4324
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.
$


----------------------------------


template < int N, typename T >
class A
{ 
  enum alignas (N) E : T;
};

A < 1, char > a;