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Before this patch, the value of DW_AT_bit_offset, used for bitfields before DWARF version 4, was always emitted as an unsigned integer using the form DW_FORM_data<n>. If the value was originally a signed integer, for instance in the case of negative offsets, it was up to debug information consumers to re-cast it to a signed integer. This is problematic since the burden of deciding if the value should be read as signed or unsigned was put onto the debug info consumers: the DWARF specification doesn't define DW_AT_bit_offset's underlying type. If a debugger decided to interpret this attribute in the form data<n> as unsigned, then negative offsets would be completely broken. The DWARF specification version 3 mentions in the Data Representation section, page 127: > If one of the DW_FORM_data<n> forms is used to represent a signed or unsigned integer, it can be hard for a consumer to discover the context necessary to determine which interpretation is intended. Producers are therefore strongly encouraged to use DW_FORM_sdata or DW_FORM_udata for signed and unsigned integers respectively, rather than DW_FORM_data<n>. Therefore, the proposal is to use DW_FORM_sdata, which is explicitly signed. This is an indication to consumers that the offset must be parsed unambiguously as a signed integer. Finally, gcc already uses DW_FORM_sdata for negative offsets, fixing the potential ambiguity altogether. This patch mimics gcc's behaviour by emitting negative values of DW_AT_bit_offset using the DW_FORM_sdata form. This eliminates any potential misinterpretation. One could argue that all values should use DW_FORM_sdata, but for the sake of parity with gcc, it is safe to restrict the change to negative values.