On Mon, 2018-06-04 at 16:16 +0000, Sasha Da Rocha Pinheiro wrote: > We had a case where dwarf_next_cfi returns -1 but the offset does not > update, as we should expect by the comment: > > 330 On errors, returns -1. Some format errors will permit safely > 331 skipping to the next CFI entry though the current one is > unusable. > 332 In that case, *NEXT_OFF will be updated before a -1 return. > Is there a correct way to deal with it, or just check if the NEXT_OFF > had changed?
A CFI entry starts with the length of that entry, so dwarf_next_cfi can often setup the next offset correctly. But if there is anything else "wrong" with the CFI entry (maybe it has a version or augmentation string not recognized) then it cannot reliably return the CFI entry. It is indeed a slightly inconvenient interface, you'll have to check whether the return value, if it is zero, all is fine, if it is 1 you reached the end, if it is -1 an error occurred. In that last case, if you really want to try you can try. *next_off having changed after the call means it might work (or not). If you have an example of a "wrong" (or not recognized) CFI that would be helpful. Thanks, Mark
