[Bug c++/71511] New: ICE on valid C++11 code (with decltype) on x86_64-linux-gnu: in cxx_incomplete_type_diagnostic, at cp/typeck2.c:567

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71511

            Bug ID: 71511
           Summary: ICE on valid C++11 code (with decltype) on
                    x86_64-linux-gnu: in cxx_incomplete_type_diagnostic,
                    at cp/typeck2.c:567
           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 at least 4.8.x and later. 


$ 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++-trunk -std=c++11 -c small.cpp
small.cpp:8:52: internal compiler error: in cxx_incomplete_type_diagnostic, at
cp/typeck2.c:567
 template < typename T > int decltype (A < T > ())::i = 100;
                                                    ^
0x726173 cxx_incomplete_type_diagnostic(unsigned int, tree_node const*,
tree_node const*, diagnostic_t)
        ../../gcc-source-trunk/gcc/cp/typeck2.c:567
0x7be5b5 cxx_incomplete_type_diagnostic
        ../../gcc-source-trunk/gcc/cp/cp-tree.h:6740
0x7be5b5 complete_type_or_maybe_complain(tree_node*, tree_node*, int)
        ../../gcc-source-trunk/gcc/cp/typeck.c:151
0x6a715f grokdeclarator(cp_declarator const*, cp_decl_specifier_seq*,
decl_context, int, tree_node**)
        ../../gcc-source-trunk/gcc/cp/decl.c:10564
0x6aa806 start_decl(cp_declarator const*, cp_decl_specifier_seq*, int,
tree_node*, tree_node*, tree_node**)
        ../../gcc-source-trunk/gcc/cp/decl.c:4827
0x7aa4b2 cp_parser_init_declarator
        ../../gcc-source-trunk/gcc/cp/parser.c:18566
0x7ac051 cp_parser_single_declaration
        ../../gcc-source-trunk/gcc/cp/parser.c:25876
0x7ac18c cp_parser_template_declaration_after_parameters
        ../../gcc-source-trunk/gcc/cp/parser.c:25481
0x7acb98 cp_parser_explicit_template_declaration
        ../../gcc-source-trunk/gcc/cp/parser.c:25709
0x7acb98 cp_parser_template_declaration_after_export
        ../../gcc-source-trunk/gcc/cp/parser.c:25727
0x7b47e9 cp_parser_declaration
        ../../gcc-source-trunk/gcc/cp/parser.c:12092
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
0x7b34f8 c_parse_file()
        ../../gcc-source-trunk/gcc/cp/parser.c:37486
0x917072 c_common_parse_file()
        ../../gcc-source-trunk/gcc/c-family/c-opts.c:1064
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 < typename T > 
class A 
{   
  static int i;   
};

//okay: template < typename T > int A <T>::i = 100;
template < typename T > int decltype (A < T > ())::i = 100;