In DWARF v3, section 7.20 deals with the structure of the debug_aranges section. Near the end, there is the following paragraph:
"This header is followed by a series of tuples. Each tuple consists of an address and a length, each in the size appropriate for an address on the target architecture. The first tuple following the header in each set begins at an offset that is a multiple of the size of a single tuple (that is, twice the size of an address). The header is padded, if necessary, to the appropriate boundary. Each set of tuples is terminated by a 0 for the address and 0 for the length." Note the third sentence: "The first tuple following the header in each set begins at an offset that is a multiple of the size of a single tuple (that is, twice the size of an address)." Meanwhile in DWARFv4, section 6.1.2, which describes the same, the corresponding fragment goes: "This header is followed by a variable number of address range descriptors. Each descriptor is a triple consisting of a segment selector, the beginning address within that segment of a range of text or data covered by some entry owned by the corresponding compilation unit, followed by the non-zero length of that range. A particular set is terminated by an entry consisting of three zeroes. When the segment_size value is zero in the header, the segment selector is omitted so that each descriptor is just a pair, including the terminating entry. By scanning the table, a debugger can quickly decide which compilation unit to look in to find the debugging information for an object that has a given address. If the range of addresses covered by the text and/or data of a compilation unit is not contiguous, then there may be multiple address range descriptors for that compilation unit." Note that there is no mention of the triple/tuple alignment requirement. The version number in the aranges CU header is supposed to be 2 both in DWARF v4 and DWARF v3. Meanwhile, the alignment or lack thereof does make a difference for a parser. Is there a preferred way to disambiguate?
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