[Bug c++/79380] New: ICE on C++11 code with illegal alignas specifier on x86_64-linux-gnu: unexpected expression ‘f’ of kind overload

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79380

            Bug ID: 79380
           Summary: ICE on C++11 code with illegal alignas specifier on
                    x86_64-linux-gnu: unexpected expression ‘f’ of kind
                    overload
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu
  Target Milestone: ---

It seems to affect all versions 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/7.0.1/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 7.0.1 20170204 (experimental) [trunk revision 245182] (GCC)
$
$ g++-trunk -std=c++11 -c small.cpp
small.cpp:4:17: internal compiler error: unexpected expression ‘f’ of kind
overload
 struct alignas (f) S {};
                 ^
0x8d4f9e cxx_eval_constant_expression
        ../../gcc-source-trunk/gcc/cp/constexpr.c:4533
0x8da649 cxx_eval_outermost_constant_expr
        ../../gcc-source-trunk/gcc/cp/constexpr.c:4591
0x7c05bb cp_parser_std_attribute_spec
        ../../gcc-source-trunk/gcc/cp/parser.c:24962
0x7c05bb cp_parser_std_attribute_spec_seq
        ../../gcc-source-trunk/gcc/cp/parser.c:25002
0x7aa6f5 cp_parser_class_head
        ../../gcc-source-trunk/gcc/cp/parser.c:22414
0x7aa6f5 cp_parser_class_specifier_1
        ../../gcc-source-trunk/gcc/cp/parser.c:22032
0x7ac3d9 cp_parser_class_specifier
        ../../gcc-source-trunk/gcc/cp/parser.c:22344
0x7ac3d9 cp_parser_type_specifier
        ../../gcc-source-trunk/gcc/cp/parser.c:16408
0x7c40f3 cp_parser_decl_specifier_seq
        ../../gcc-source-trunk/gcc/cp/parser.c:13325
0x7ce2a0 cp_parser_simple_declaration
        ../../gcc-source-trunk/gcc/cp/parser.c:12649
0x7cf161 cp_parser_block_declaration
        ../../gcc-source-trunk/gcc/cp/parser.c:12594
0x7d5f30 cp_parser_declaration
        ../../gcc-source-trunk/gcc/cp/parser.c:12491
0x7d6334 cp_parser_declaration_seq_opt
        ../../gcc-source-trunk/gcc/cp/parser.c:12367
0x7d6678 cp_parser_translation_unit
        ../../gcc-source-trunk/gcc/cp/parser.c:4366
0x7d6678 c_parse_file()
        ../../gcc-source-trunk/gcc/cp/parser.c:38382
0x93e552 c_common_parse_file()
        ../../gcc-source-trunk/gcc/c-family/c-opts.c:1107
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.
$


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template < typename > constexpr int f () {  return 8;  }

// should have been: struct alignas (f<int>()) S {};
struct alignas (f) S {};