[RFA/DWARF2] Emit enumeration_type DIE for enum subtypes

[Joel Brobecker <brobecker at gnat dot com>]

Hello,

While trying to debug a program built with dwarf-2, we noticed the
following problem when trying to print the value of a variable whose
type is derived from an enumeration type.

On x86-linux for instance, build the following small program:

        Procedure A is
           type Enum is (First, Second, Last);
           type Sized_Enum is new Enum;
           X : Sized_Enum := First;
        Begin
           X := Second;
        End A;

With the following command:

        % gnatmake -gdwarf-2 a

The problem can be demonstrated as follow:

        % gdb a
        (gdb) begin
        (gdb) ptype sized_enum
        type = range 0 .. 2

The expected output is (as obtained when built with -gstabs+):

        (gdb) ptype sized_enum
        type = range first .. last

We believe that the problem is in the dwarf2 data generated by GCC.
Here is what is currently generated by GCC (from CVS head):

        .uleb128 0x3    # (DIE (0x152) DW_TAG_base_type)
        .ascii "a__sized_enum___XDLU_0__2\0"    # DW_AT_name
        .byte   0x1     # DW_AT_byte_size
        .byte   0x7     # DW_AT_encoding

I believe that sized_enum should instead be defined as a subrange
type. With the attached patch, here is what is now generated:

        .uleb128 0x6    # (DIE (0x119) DW_TAG_subrange_type)
        .ascii "a__sized_enum___XDLU_0__2\0"    # DW_AT_name
        .byte   0x0     # DW_AT_lower_bound
        .byte   0x2     # DW_AT_upper_bound
        .long   0x173   # DW_AT_type

and type DIE 0x173 is:

        .uleb128 0xa    # (DIE (0x173) DW_TAG_enumeration_type)
        .long   0x1be   # DW_AT_sibling
        .ascii "a__sized_enumB\0"       # DW_AT_name
        .byte   0x1     # DW_AT_byte_size 
        [...]

2004-01-07  J. Brobecker  <brobecker@gnat.com>

        * dwarf2out.c (gen_enumeration_type_die): Return the DIE that
        we just created.
        (is_ada_subrange_type): DIEs for enumeration subtypes should be
        emitted as subrange types too.
        (subrange_type_die): Add handling of enumeration subtypes.

tested on x86-linux, by bootstrapping GCC and against the testsuite.

OK to apply?

Thanks,
-- 
Joel

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