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Created October 20, 2021 23:07
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dwarf_d_issues.md

DWARF Generation on D compilers

  • DMD lacks information about DW_AT_decl_file, DW_AT_decl_line and DW_AT_decl_column on some tags.
  • LDC lacks information about DW_AT_decl_column.
  • LDC generates artificial DWARF variables and don't properly mark then as DW_AT_artificial.

Types

  • GDC produces an error on LLDB:

    error: need to add support for DW_TAG_base_type 'dchar' encoded with DW_ATE = 0x8, bit_size = 32

  • DMD for some reason, unknown to my current compiler knowledge, is generating _Bool type name for bool types.

Enumerations

  • DMD has a bug with DW_TAG_enumerator. Currently that information is not being generated.

Arrays

  • No D compiler generates correct DWARF tags to represent dynamic arrays. They should use DW_TAG_array_type with DW_TAG_subrange_type and reference the size of it using DW_AT_count/DW_AT_upper_bound variable address or manually dereference a stack register, containing the size. This approach is used by C compilers when dealing with VLAs.

Normal Arrays

  • Every D compiler except DMD handles normal array type names with fully qualified names. I already pushed a fix to this.

  • Every D compiler writes array DWARF information as a struct with length and ptr fields.

  • No D compiler generates special DWARF tags when dealing with string arrays.

Associative Arrays

  • DMD has a bug for associative arrays with array types, reporting the wrong type in the name.

    For an int[string] it reports _AArray_ucent_int For an string[int] it reports _AArray_int_ucent

  • Every D compiler except DMD handles associative array types with fully qualified names.

  • Associative array struct is not accessible on any D compiler

Interfaces

  • GDC uses DW_TAG_interface_type tags including DW_AT_containing_type pointing to themselves as part of GNU extensions to DWARF, triggering an error on LLDB. This tag is not part of the DWARF structure for interfaces.
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