Crash when trying to access 'length(0) for multi-dimensional array

[bpadalino]

When trying to access the attribute 'length(0) for a 2-d array, a crash occurs.

entity test is
end entity ;

architecture arch of test is

    type real_matrix is array (natural range <>, natural range <>) of real ;
    constant m : real_matrix := ( (1.0, 2.0, 3.0, 4.0), (2.0, 3.0, 4.0, 5.0) ) ;

    procedure print(x : in string) is
        variable l : std.textio.line ;
    begin
        std.textio.write(l, x) ;
        std.textio.writeline(std.textio.output, l) ;
    end procedure ;

begin

    tb : process
    begin
        print("m length: " & integer'image(m'length(0))) ;
        std.env.stop ;
    end process ;

end architecture ;

$ nvc --std=2008 -a attribute_value.vhdl -e test -r

Name       WORK.TEST.TB
Kind       process
Context    WORK.TEST
Blocks     2
Registers  14
Types      15
Variables  0
Begin
   0: return 
   1: r0 := context upref 1             // P<WORK.TEST>
      r1 := const 109                   // 0..255 => 109
      r2 := const 32                    // 0..255 => 32
      r3 := const 108                   // 0..255 => 108
      r4 := const 101                   // 0..255 => 101
      r5 := const 110                   // 0..255 => 110
      r6 := const 103                   // 0..255 => 103
      r7 := const 116                   // 0..255 => 116
      r8 := const 104                   // 0..255 => 104
      r9 := const 58                    // 0..255 => 58
      r10 := const [r1,r2,r3,r4,r5,r6,r7,r8,r9,r2] // [10] : 0..255 => 0..255
      r11 := address of r10             // @<0..255> => 0..255
      r12 := var upref 1, M             // @<[*, *] : %> => %
      r13 := load indirect r12          // [*, *] : % => %
      invalid := uarray len r13 dim -1   <----

** Fatal: invalid dimension -1
[0x5644f5fa0e9c] ../src/diag.c:1011 diag_femit
[0x5644f5fa0e9c] ../src/diag.c:1036 diag_emit
[0x5644f5edbdb2] ../src/util.c:585 fatal_trace
[0x5644f5f8f862] ../src/vcode.c:4636 emit_uarray_len
[0x5644f5f6d75c] ../src/lower.c:4884 lower_attr_ref
[0x5644f5f6d75c] ../src/lower.c:5249 lower_expr.lto_priv.0
[0x5644f5f8729d] ../src/lower.c:12618 lower_rvalue
[0x5644f5f68de4] ../src/lower.c:4799 lower_attr_param.lto_priv.0
[0x5644f5f6d808] ../src/lower.c:4989 lower_attr_ref
[0x5644f5f6d808] ../src/lower.c:5249 lower_expr.lto_priv.0
[0x5644f5f8729d] ../src/lower.c:12618 lower_rvalue
[0x5644f5f5bcd1] ../src/lower.c:2042 lower_flatten_concat
[0x5644f5f6296c] ../src/lower.c:2053 lower_concat.lto_priv.0
[0x5644f5f6c39f] ../src/lower.c:5223 lower_expr.lto_priv.0
[0x5644f5f8729d] ../src/lower.c:12618 lower_rvalue
[0x5644f5f61def] ../src/lower.c:1127 lower_subprogram_arg.lto_priv.0
[0x5644f5f6f02f] ../src/lower.c:6530 lower_pcall
[0x5644f5f6f8b5] ../src/lower.c:7378 lower_sequence.lto_priv.0
[0x5644f5f44869] ../src/lower.c:11352 elab_stmts.lto_priv.0
[0x5644f5f3ceb9] ../src/elab.c:1489 elab_architecture.lto_priv.0
[0x5644f6009209] ../src/elab.c:2091 elab_top_level.constprop.0
[0x5644f5f41d90] ../src/elab.c:2154 elab
[0x5644f5ee4a4a] ../src/nvc.c:464 elaborate
[0x5644f5ee1c9f] ../src/nvc.c:1921 process_command
[0x5644f5ee20dc] ../src/nvc.c:1041 init_cmd
[0x5644f5ee20dc] ../src/nvc.c:1935 process_command
[0x5644f5ed9845] ../src/nvc.c:2059 main

When accessing a real_vector, the error appears:

** Error: invalid dimension 0 for type REAL_VECTOR
    > attribute_value.vhdl:19
    |                                                                                 
 19 |         print("v length: " & integer'image(v'length(0))) ;
    |                                                     ^