[Bug c++/70572] New: ICE on code with decltype (auto) on x86_64-linux-gnu in digest_init_r, at cp/typeck2.c:1103 with -std=c++14

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70572

            Bug ID: 70572
           Summary: ICE on code with decltype (auto) on x86_64-linux-gnu
                    in digest_init_r, at cp/typeck2.c:1103 with -std=c++14
           Product: gcc
           Version: 6.0
            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 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 4.9.x and later, which support -std=c++14. 


$ 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/6.0.0/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 6.0.0 20160406 (experimental) [trunk revision 234771] (GCC) 
$ 
$ g++-trunk -c -std=c++14 small.cpp
small.cpp: In function ‘int foo()’:
small.cpp:3:23: internal compiler error: in digest_init_r, at cp/typeck2.c:1103
   decltype (auto) a = foo;   // OK: decltype (auto) a = &foo;
                       ^~~
0x6cd59c digest_init_r
        ../../gcc-source-trunk/gcc/cp/typeck2.c:1099
0x6cf2ea digest_init_flags
        ../../gcc-source-trunk/gcc/cp/typeck2.c:1168
0x6cf2ea store_init_value(tree_node*, tree_node*, vec<tree_node*, va_gc,
vl_embed>**, int)
        ../../gcc-source-trunk/gcc/cp/typeck2.c:802
0x62fbf4 check_initializer
        ../../gcc-source-trunk/gcc/cp/decl.c:6162
0x659865 cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int)
        ../../gcc-source-trunk/gcc/cp/decl.c:6810
0x752f9f cp_parser_init_declarator
        ../../gcc-source-trunk/gcc/cp/parser.c:18658
0x753750 cp_parser_simple_declaration
        ../../gcc-source-trunk/gcc/cp/parser.c:12379
0x753a61 cp_parser_block_declaration
        ../../gcc-source-trunk/gcc/cp/parser.c:12248
0x7544b8 cp_parser_declaration_statement
        ../../gcc-source-trunk/gcc/cp/parser.c:11860
0x732b7b cp_parser_statement
        ../../gcc-source-trunk/gcc/cp/parser.c:10528
0x73349c cp_parser_statement_seq_opt
        ../../gcc-source-trunk/gcc/cp/parser.c:10806
0x73358f cp_parser_compound_statement
        ../../gcc-source-trunk/gcc/cp/parser.c:10760
0x751dcf cp_parser_function_body
        ../../gcc-source-trunk/gcc/cp/parser.c:20653
0x751dcf cp_parser_ctor_initializer_opt_and_function_body
        ../../gcc-source-trunk/gcc/cp/parser.c:20689
0x752871 cp_parser_function_definition_after_declarator
        ../../gcc-source-trunk/gcc/cp/parser.c:25351
0x753467 cp_parser_function_definition_from_specifiers_and_declarator
        ../../gcc-source-trunk/gcc/cp/parser.c:25263
0x753467 cp_parser_init_declarator
        ../../gcc-source-trunk/gcc/cp/parser.c:18429
0x753750 cp_parser_simple_declaration
        ../../gcc-source-trunk/gcc/cp/parser.c:12379
0x753a61 cp_parser_block_declaration
        ../../gcc-source-trunk/gcc/cp/parser.c:12248
0x75c5d0 cp_parser_declaration
        ../../gcc-source-trunk/gcc/cp/parser.c:12145
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.
$ 


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


int foo ()
{
  decltype (auto) a = foo;  // OK: decltype (auto) a = &foo;
  return 0; 
}