That sounds like a plan. I have started cleaning up the class a bit (removing manual uuid string formatting in various places and such), and then I'll send a patch which implements that.
Leonard, I'm not going to use your patch, as it's a bit un-llvm-y (uses std::ostream and such). However, I wanted to check whether 20 bytes will be enough for your use cases (uuids in minidumps)? On Thu, 21 Jun 2018 at 16:03, Greg Clayton <clayb...@gmail.com> wrote: > > I am fine if we go with any number of bytes. We should have the > lldb_private::UUID class have an array of bytes that is in the class that is > to to 20 bytes. We can increase it later if needed. I would rather not have a > dynamically allocated buffer. > > That being said a few points: > - Length can be set to zero to indicate invalid UUID. Better that than > filling in all zeroes and having to check for that IMHO. I know there were > some problems with the last patch around this. > - Don't set length to a valid value and have UUID contain zeros unless that > is a true UUID that was calculated. LLDB does a lot of things by matching > UUID values so we can't have multiple modules claiming to have a UUID that is > filled with zeroes, otherwise many matches will occur that we don't want > - 32 bit GNU debug info CRCs from ELF notes could be filled in as 4 byte UUIDs > - Comparing two UUIDs can start with the length field first the if they match > proceed to compare the bytes (which is hopefully what is already happening) > > > On Jun 20, 2018, at 11:01 AM, Leonard Mosescu via lldb-dev > <lldb-dev@lists.llvm.org> wrote: > > Here's a snapshot of the old changes I had: https://reviews.llvm.org/D48381 > (hopefully it helps a bit but caveat emptor: this is a quick merge from an > old patch, so it's for illustrative purposes only) > > > On Wed, Jun 20, 2018 at 10:26 AM, Pavel Labath <lab...@google.com> wrote: >> >> From the looks of it, the patch stalled on the part whether we can >> consider all-zero UUIDs as valid or not. I've dug around the code a >> bit now, and I've found this comment in ObjectFileMachO.cpp. >> >> // "main bin spec" (main binary specification) data payload is >> // formatted: >> // uint32_t version [currently 1] >> // uint32_t type [0 == unspecified, 1 == >> kernel, 2 == user process] >> // uint64_t address [ UINT64_MAX if address not >> specified ] >> // uuid_t uuid [ all zero's if uuid not specified ] >> // uint32_t log2_pagesize [ process page size in log >> base 2, e.g. 4k pages are 12. 0 for unspecified ] >> >> >> So it looks like there are situations where we consider all-zero UUIDs >> as invalid. >> >> I guess that means we either have to keep IsValid() definition as-is, >> or make ObjectFileMachO check the all-zero case itself. (Some middle >> ground may be where we have two SetFromStringRef functions, one which >> treats all-zero case specially (sets m_num_uuid_bytes to 0), and one >> which doesn't). Then clients can pick which semantics they want. >> >> >> > 1. A variable-length UUID likely incurs an extra heap allocation. >> Not really. If you're happy with the current <=20 limit, then you can >> just use the existing data structure. Otherwise, you could use a >> SmallVector<uint8_t, 20>. >> >> > 2. Formatting arbitrary length UUIDs as string is a bit inconvenient as >> > you noted as well. >> For the string representation, I would say we should just use the >> existing layout of dashes (after 4, 6, 8, 10 and 16 bytes) and just >> cut it short when we have less bytes. The implementation of that >> should be about a dozen lines of code. >> >> The fact that these new UUIDs would not be real UUIDs could be solved >> by renaming this class to something else, if anyone can think of a >> good name for it (I can't). Then the "real" UUIDs will be just a >> special case of the new object. >> >> pl > > > _______________________________________________ > lldb-dev mailing list > lldb-dev@lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev > > _______________________________________________ lldb-dev mailing list lldb-dev@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
