[Bug c++/60249] New: [c++11] Compiler goes into semi-infinite loop with wrong usage of user defined string literals

["reichelt at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60249

            Bug ID: 60249
           Summary: [c++11] Compiler goes into semi-infinite loop with
                    wrong usage of user defined string literals
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Keywords: ice-on-invalid-code
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: reichelt at gcc dot gnu.org

The following invalid code snippet (compiled with "-std=c++11") triggers
an ICE since GCC 4.7.0 (when user defined literals were introduced):

====================================
decltype( ""_ ) x;
====================================

The compiler goes into a loop and finally crashes:

bug.cc:1:11: error: unable to find string literal operator 'operator""_'
 decltype( ""_ ) x;
           ^
bug.cc:1:11: warning: unknown escape sequence: '\257'
bug.cc:1:11: warning: unknown escape sequence: '\000'
bug.cc:1:11: warning: unknown escape sequence: '\000'
bug.cc:1:11: warning: unknown escape sequence: '\000'
bug.cc:1:11: warning: unknown escape sequence: '\000'
bug.cc:1:11: warning: unknown escape sequence: '\000'
bug.cc:1:11: warning: unknown escape sequence: '\000'
bug.cc:1:11: warning: unknown escape sequence: '\000'
bug.cc:1:11: warning: unknown escape sequence: '\000'

[ snip more than a million lines ]

bug.cc:1:11: warning: unknown escape sequence: '\000'
bug.cc:1:11: warning: unknown escape sequence: '\000'
bug.cc:1:11: warning: unknown escape sequence: '\000'
bug.cc:1:11: warning: unknown escape sequence: '\000'
bug.cc:1:11: internal compiler error: Segmentation fault
0xba529f crash_signal
    ../../gcc/gcc/toplev.c:337
0x114a0f8 convert_escape
    ../../gcc/libcpp/charset.c:1271
0x114a0f8 cpp_interpret_string(cpp_reader*, cpp_string const*, unsigned long,
cpp_string*, cpp_ttype)
    ../../gcc/libcpp/charset.c:1435
0x6a4f63 cp_parser_string_literal
    ../../gcc/gcc/cp/parser.c:3653
0x6afa21 cp_parser_primary_expression
    ../../gcc/gcc/cp/parser.c:4224
0x6b20dd cp_parser_postfix_expression
    ../../gcc/gcc/cp/parser.c:5971
0x6b50b6 cp_parser_unary_expression
    ../../gcc/gcc/cp/parser.c:7170
0x6b5ddf cp_parser_binary_expression
    ../../gcc/gcc/cp/parser.c:7874
0x6b62d1 cp_parser_assignment_expression
    ../../gcc/gcc/cp/parser.c:8112
0x6b8684 cp_parser_expression
    ../../gcc/gcc/cp/parser.c:8274
0x6b36cd cp_parser_decltype_expr
    ../../gcc/gcc/cp/parser.c:11924
0x6b36cd cp_parser_decltype
    ../../gcc/gcc/cp/parser.c:12003
0x6cb40f cp_parser_simple_type_specifier
    ../../gcc/gcc/cp/parser.c:14533
0x6a942d cp_parser_type_specifier
    ../../gcc/gcc/cp/parser.c:14380
0x6c2b40 cp_parser_decl_specifier_seq
    ../../gcc/gcc/cp/parser.c:11547
0x6c9739 cp_parser_simple_declaration
    ../../gcc/gcc/cp/parser.c:11137
0x6acc03 cp_parser_block_declaration
    ../../gcc/gcc/cp/parser.c:11086
0x6d3ea2 cp_parser_declaration
    ../../gcc/gcc/cp/parser.c:10983
0x6d2b98 cp_parser_declaration_seq_opt
    ../../gcc/gcc/cp/parser.c:10869
0x6d443a cp_parser_translation_unit
    ../../gcc/gcc/cp/parser.c:4014
Please submit a full bug report, [etc.]

Although error-recovery bugs usually end up as P5, I'd vote for
prioritizing this one higher: the amount of output (60 MB in my case)
is worse than the crash.