allow SESSION_READ_ONLY open a DBI book without write privileges

[John Ralls]

Indeed it is. But IIRC upgrading code is a major undertaking that Derek doesn’t have time for.

Do you remember offhand what feature if any you used in that change that prompted raising the Doxygen version?

Regards,
John Ralls


> On Jul 13, 2026, at 07:58, Geert Janssens <geert.gnucash at kobaltwit.be> wrote:
> 
> Fedora 29 is quite old by now...
> 
> Op maandag 13 juli 2026 02:28:16 Midden-Europese zomertijd schreef Derek Atkins:
> > Maybe that was the issue.
> >
> > [root at code ~]# rpm -q doxygen
> > doxygen-1.8.14-7.fc29.x86_64
> >
> > -derek
> >
> > On Sun, July 12, 2026 2:10 pm, John Ralls wrote:
> > > Derek,
> > >
> > > That doesn’t square with the last build being two years ago, we removed
> > > auto tools in 2017. https://github.com/Gnucash/gnucash/pull/1943, which
> > > was merged immediately after the last successful docs build is the
> > > culprit. What version of Doxygen are you running?
> > > https://github.com/Gnucash/gnucash/pull/1943/changes/891b921c811f32e214fe9
> > > fc1a87e392b58ed7757 bumped the Doxyfile version from 1.8.3 to 1.9.7.
> > >
> > > Regards,
> > > John Ralls
> > >
> > >> On Jul 11, 2026, at 18:08, Derek Atkins <derek at ihtfp.com> wrote:
> > >>
> > >> Yes, doxygen not building is a known issue.  The build requirements
> > >> changed and I've never spent the time to figure out how to update the
> > >> script to meet the new requirements.  Specifically I used to be able to
> > >> build the doxygen.cfg manually by calling the Makefile.am with the right
> > >> rule.  But that was removed for CMake, and I think to get that to work I
> > >> might need to install a complete build system, which I kinda don't want
> > >> to do.  Worst case I'll have to make VM just for that..  But it just
> > >> hasn't been high on my priority list.
> > >> -derek
> > >> Sent using my mobile device. Please excuse any typos.
> > >>
> > >> On July 11, 2026 16:18:15 John Ralls <jralls at ceridwen.us> wrote:
> > >>> Noah,
> > >>>
> > >>> Please always copy one of the mailing lists when you email one of the
> > >>> GnuCash developers unless it’s to send something like a GnuCash book;
> > >>> in that case the email should just have the file, all of the discussion
> > >>> around it should be copied to the list.
> > >>>
> > >>> I’ve passed on to Derek via IRC the Doxygen-docs problem just in case
> > >>> he misses it here.
> > >>>
> > >>> Yup, readonly-mode is largely cosmetic and applied only to the GUI.
> > >>> GnuCash is not designed for use by more than one user at a time and
> > >>> read-only mode is very simplistic.
> > >>>
> > >>> I don’t think it would be too hard to extend its force to the backend
> > >>> so that a read-only session is blocked from writing. But if you want a
> > >>> read-only session to lock the database then it’s not really read-only
> > >>> anymore.
> > >>>
> > >>> How about leveraging the database’s locking? Wrap all of the queries
> > >>> with dbi_conn_transaction_begin and dbi_conn_transaction_commit. That
> > >>> will make multi-table writes atomic with an exclusive lock, blocking a
> > >>> reader from reading them until the whole write is complete, while a
> > >>> read query while loading will block the exclusive write lock until the
> > >>> read is complete.
> > >>>
> > >>> Regards,
> > >>> John Ralls
> > >>>
> > >>>> On Jul 11, 2026, at 12:24 PM, array_hourly_0u at icloud.com wrote:
> > >>>>
> > >>>> Thanks for merging #2264 and #2266 John.
> > >>>>
> > >>>> Arrg.  As I've started to poke more into this read-only and lock
> > >>>> topic, I've found some surprises and ultimately a correctness matter.
> > >>>>
> > >>>> What SESSION_READ_ONLY actually means
> > >>>> ------------------------------------------------------------
> > >>>>
> > >>>> 1. At the engine level, SESSION_READ_ONLY doesn't actually enforce
> > >>>> read-only. The mode only affects lock handling -- it does not mark the
> > >>>> book read-only. Book write-protection is applied separately by the GUI
> > >>>> only, which calls qof_book_mark_readonly() after opening. I confirmed
> > >>>> with an API bindings test that a SESSION_READ_ONLY session can still
> > >>>> edit an account and have the change persisted to the SQL store. So an
> > >>>> API/bindings consumer that opens SESSION_READ_ONLY expecting the book
> > >>>> to be unwritable does not get that guarantee unless it also calls
> > >>>> qof_book_mark_readonly() itself. [a bug if one interprets
> > >>>> SESSION_READ_ONLY reading the enum name while not carefully parsing
> > >>>> the header comments ]
> > >>>>
> > >>>> 2.  SESSION_READ_ONLY ignores the lock. A read-only consumer opens a
> > >>>> book even while another process holds it open, perhaps mid-write,
> > >>>> which is exactly when the state can be inconsistent; and because the
> > >>>> SQL backend commits incrementally, a reader can catch a
> > >>>> partially-applied edit. [ a read-only client correctness bug ]
> > >>>>
> > >>>> So today the mode neither protects read consistency (it ignores the
> > >>>> lock) nor guarantees read-only-ness (that's a GUI add-on), even though
> > >>>> the name implies both.
> > >>>>
> > >>>> Proposed path forward
> > >>>> -----------------------------------
> > >>>>
> > >>>> For building read-only tools on the API, what I'd want is a read-only
> > >>>> session mode that (a) takes the lock, so a writer cannot be active
> > >>>> while the tool reads, and (b) actually enforces no writes.
> > >>>>
> > >>>> A possible direction would be to replace SESSION_READ_ONLY with two
> > >>>> modes whose names state what they do, and have both mark the book
> > >>>> read-only so enforcement is intrinsic rather than GUI-only:
> > >>>> - SESSION_READ_ONLY_EXCLUSIVE -- takes the lock (fails if the book is
> > >>>> already locked); for tools that need a consistent, uninterrupted read.
> > >>>> Calls qof_book_mark_readonly(). Obviously a SQL backend user would
> > >>>> need sufficient permissions to take the lock.  I'd want to add some
> > >>>> user guide documentation about this where none exists today.
> > >>>> - SESSION_READ_ONLY_IGNORE_LOCK -- opens regardless of the lock state;
> > >>>> the path the GUI's "open read-only anyway" override would use. (i.e.
> > >>>> today's SESSION_READ_ONLY behavior, but with qof_book_mark_readonly()
> > >>>> )
> > >>>>
> > >>>> These could be added now, with SESSION_READ_ONLY marked deprecated,
> > >>>> and SESSION_READ_ONLY removed in a later release (v6? whatever that
> > >>>> timeframe turns out to be).  I believe the deprecation warning would
> > >>>> only apply to users of the API `SESSION_READ_ONLY` mode today. (The
> > >>>> GUI internal use would be swapped to SESSION_READ_ONLY_IGNORE_LOCK.)"
> > >>>>
> > >>>> Does folding read-only enforcement into the mode (so bindings
> > >>>> consumers get it too), plus splitting the lock behavior, sound like an
> > >>>> OK path?
> > >>>>
> > >>>> Aside,  is it a known issue Doxygen isn't updating / is stale? (title
> > >>>> says "GnuCash  5.6-150-g038405b370+" )
> > >>>> https://code.gnucash.org/docs/STABLE/qofsession_8h.html
> > >>>> I was initially looking for the enum descriptions but didn't find them
> > >>>> outside of the code.  Double btw:  There is a documentation bug in the
> > >>>> source here in that the five /** … */ comments need to be trailing
> > >>>> /**< … */ comments (Doxygen trailing-member syntax).  Right now, when
> > >>>> the comments are rendered, they are offset by one.
> > >>>>
> > >>>> Regards,
> > >>>>
> > >>>> Noah
> > >>>>
> > >>>> On Sat, Jul 11, 2026 at 8:47 AM Noah <> wrote:
> > >>>>> Thanks, John.
> > >>>>>
> > >>>>>> Your premise that the database was necessarily written by a GnuCash
> > >>>>>> session is false.
> > >>>>>
> > >>>>> You're right, I was biasing by my own use principles.
> > >>>>> I never want to modify my production book through anything but the
> > >>>>> GnuCash GUI or the official GnuCash API / bindings.
> > >>>>>
> > >>>>> My household moved our finances to GnuCash 14 years ago motivated by
> > >>>>> two challenges.
> > >>>>> - need to support two users on different computers (in serial, not
> > >>>>> simultaneously). We were bit too many times with filesystem-based
> > >>>>> commercial options at the time.
> > >>>>> - a Q* commercial software was dropping support for Mac, or
> > >>>>> non-cloud, or both
> > >>>>>
> > >>>>> In more recent years, our financial institutions have been making it
> > >>>>> harder to get our transaction data into GnuCash (eg. removing OFX/QFX
> > >>>>> download)
> > >>>>> In order to hold the line at home, I've been doing more and more work
> > >>>>> adopting use of the  API & Python bindings to help a lot in this
> > >>>>> regard.  I've also been creating some reporting and exploration tools
> > >>>>> that don't need write access (and tinkering with other's work like
> > >>>>> piecash). Since they don’t need write access, I want them to access
> > >>>>> MySQL with the minimum privileges necessary.
> > >>>>>
> > >>>>>> The ffastmath problem underlying bug 611936 was on the write side of
> > >>>>>> libdii so a read-only test wouldn’t find the problem.
> > >>>>>
> > >>>>> That settles it for me: since the -ffast-math defect in #611936 is on
> > >>>>> the write side of libdbi, a read-only session can neither trigger nor
> > >>>>> detect it, so running the probe on a read-only open guards nothing.
> > >>>>> I've opened a PR that skips dbi_library_test() for SESSION_READ_ONLY
> > >>>>> and leaves all write-capable modes untouched:
> > >>>>> https://github.com/Gnucash/gnucash/pull/2266
> > >>>>>
> > >>>>> I'm not trying to bolt access control onto GnuCash, and I agree that
> > >>>>> wouldn't end well. The narrower goal is just to let a read-only
> > >>>>> consumer honor a least-privilege credential a DBA may already have in
> > >>>>> place -- and, independently, to stop running a write-only probe on a
> > >>>>> read-only open. The PR stands on that second part alone.
> > >>>>>
> > >>>>> Thanks again,
> > >>>>> Noah
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>> On Thu, Jul 9, 2026 at 8:31 PM John Ralls
> > >>>>>
> > >>>>> <jralls_at_ceridwen_us_pgk183pwhb49kj_sc4m4741 at icloud.com> wrote:
> > >>>>>>> On Jul 9, 2026, at 14:34, array_hourly_0u at icloud.com wrote:
> > >>>>>>> Hello again,
> > >>>>>>> Obviously backend stuff is on my mind lately and there's been a
> > >>>>>>> quirk impacting read-only access to SQL back-ed books that has
> > >>>>>>> bothered me for a while.
> > >>>>>>> Opening a book with SESSION_READ_ONLY through the SQL/DBI backend
> > >>>>>>> still requires the database user to have permission to create a
> > >>>>>>> temporary table. On every session_begin (regardless of mode),
> > >>>>>>> dbi_library_test() runs the 64-bit round-trip guard from Bug
> > >>>>>>> #611936
> > >>>>>>> -- CREATE TEMPORARY TABLE / INSERT / SELECT / DROP -- to detect a
> > >>>>>>> 15-year-old -ffast-math libdbi miscompilation. A least-privileged,
> > >>>>>>> SELECT-only database user therefore cannot open the book at all:
> > >>>>>>> the
> > >>>>>>> create fails and begin returns ERR_SQL_DBI_UNTESTABLE.
> > >>>>>>> (SESSION_READ_ONLY already skips the gnclock lock, so this probe is
> > >>>>>>> the only remaining reason a read-only open needs write-ish rights.)
> > >>>>>>> I'd like to propose making a read-only open work without those
> > >>>>>>> privileges. Two possible directions:
> > >>>>>>> 1. Skip dbi_library_test() when the session is opened
> > >>>>>>> SESSION_READ_ONLY.
> > >>>>>>> 2. Or, for read-only, replace it with a check that needs no write
> > >>>>>>> privileges -- for example, verify the driver retrieves large
> > >>>>>>> int64/uint64 and a high-precision FLOAT8 via a SELECT of
> > >>>>>>> literals/casts (dbi_result_get_longlong / get_ulonglong /
> > >>>>>>> get_double),
> > >>>>>>> so the reader's conversion path is still validated. I'd welcome
> > >>>>>>> suggestions on the best minimal form.
> > >>>>>>> The justification for either approach: the data already in the
> > >>>>>>> database was written by a GnuCash session, and dbi_library_test()
> > >>>>>>> ran
> > >>>>>>> for that session, so any book that was successfully saved was
> > >>>>>>> necessarily saved by a driver that passed the round-trip test --
> > >>>>>>> the
> > >>>>>>> stored 64-bit and FLOAT8 values are therefore correct at rest. A
> > >>>>>>> read-only session never writes back, so the only thing left to
> > >>>>>>> guard
> > >>>>>>> against is a reader-side retrieval defect. For a modern 64-bit
> > >>>>>>> libdbi
> > >>>>>>> that is the 2011, 32-bit / -ffast-math case from #611936, which is
> > >>>>>>> essentially historical (or maybe never existed on the read)
> > >>>>>>> If there is a preferred direction, I'm happy to prepare a PR.
> > >>>>>>
> > >>>>>> Your premise that the database was necessarily written by a GnuCash
> > >>>>>> session is false. Anybody with db write access (and for a SQLite3
> > >>>>>> database that means anyone with write access to the filesystem) can
> > >>>>>> write (or delete) whatever they want into the database. There is at
> > >>>>>> least one public Python library that reads and writes GnuCash
> > >>>>>> SQLite3 files (https://github.com/sdementen/piecash). The databases
> > >>>>>> have no integrity checks enabled: Any integrity checking (and it’s
> > >>>>>> pretty minimal) is in GnuCash’s engine.
> > >>>>>>
> > >>>>>> The ffastmath problem underlying bug 611936 was on the write side of
> > >>>>>> libdii so a read-only test wouldn’t find the problem. I think it
> > >>>>>> unlikely that anyone is using that version of gcc anymore so it’s
> > >>>>>> probably safe to remove the test.
> > >>>>>>
> > >>>>>> That said, I have my doubts about the value of having users without
> > >>>>>> database write access. Access control hasn’t ever been a
> > >>>>>> consideration in GnuCash’s design and trying to bolt it on 30 years
> > >>>>>> later isn’t likely to produce a satisfactory result.
> > >>>>>>
> > >>>>>> Regards,
> > >>>>>> John Ralls
> > >>>
> > >>> _______________________________________________
> > >>> gnucash-devel mailing list
> > >>> gnucash-devel at gnucash.org
> > >>> https://lists.gnucash.org/mailman/listinfo/gnucash-devel
> > >
> > > _______________________________________________
> > > gnucash-devel mailing list
> > > gnucash-devel at gnucash.org
> > > https://lists.gnucash.org/mailman/listinfo/gnucash-devel
> 
>