The reftable library does not use the same memory allocation functions
as the rest of the Git codebase. Instead, as the reftable library is
supposed to be usable as a standalone library without Git, it provides a
set of pluggable memory allocators.
Compared to `xmalloc()` and friends these allocators are _not_ expected
to die when an allocation fails. This design choice is concious, as a
library should leave it to its caller to handle any kind of error. While
it is very likely that the caller cannot really do much in the case of
an out-of-memory situation anyway, we are not the ones to make that
decision.
Curiously though, we never handle allocation errors even though memory
allocation functions are allowed to fail. And as we do not plug in Git's
memory allocator via `reftable_set_alloc()` either the consequence is
that we'd instead segfault as soon as we run out of memory.
While the easy fix would be to wire up `xmalloc()` and friends, it
would only fix the usage of the reftable library in Git itself. Other
users like libgit2, which is about to revive its efforts to land a
backend for reftables, wouldn't be able to benefit from this solution.
Instead, we are about to do it the hard way: adapt all allocation sites
to perform error checking. Introduce a new error code for out-of-memory
errors that we will wire up in subsequent steps.
This commit also serves as the motivator for all the remaining steps in
this series such that we do not have to repeat the same arguments in
every single subsequent commit.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Code to write out reftable has seen some optimization and
simplification.
* ps/reftable-write-optim:
reftable/block: reuse compressed array
reftable/block: reuse zstream when writing log blocks
reftable/writer: reset `last_key` instead of releasing it
reftable/writer: unify releasing memory
reftable/writer: refactorings for `writer_flush_nonempty_block()`
reftable/writer: refactorings for `writer_add_record()`
refs/reftable: don't recompute committer ident
reftable: remove name checks
refs/reftable: skip duplicate name checks
refs/reftable: perform explicit D/F check when writing symrefs
refs/reftable: fix D/F conflict error message on ref copy
In the preceding commit we have disabled name checks in the "reftable"
backend. These checks were responsible for verifying multiple things
when writing records to the reftable stack:
- Detecting file/directory conflicts. Starting with the preceding
commits this is now handled by the reftable backend itself via
`refs_verify_refname_available()`.
- Validating refnames. This is handled by `check_refname_format()` in
the generic ref transacton layer.
The code in the reftable library is thus not used anymore and likely to
bitrot over time. Remove it.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We currently throw two different errors into a similar-but-different
error code:
- Errors when trying to lock the reftable stack.
- Errors when trying to write to the reftable stack which has been
modified concurrently.
This results in unclear error handling and user-visible error messages.
Create a new `REFTABLE_OUTDATED_ERROR` so that those error conditions
can be clearly told apart from each other. Adjust users of the old
`REFTABLE_LOCK_ERROR` to use the new error code as required.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
reflog entries have unbounded size. In theory, each log ('g') block in reftable
can have an arbitrary size, so the format allows for arbitrarily sized reflog
messages. However, in the implementation, we are not scaling the log blocks up
with the message, and writing a large message fails.
This triggers a failure for reftable in t7006-pager.sh.
Until this is fixed more structurally, report an error from within the reftable
library for easier debugging.
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The reftable/ directory is structured as a library, so it cannot
crash on misuse. Instead, it returns an error code.
In addition to signaling errors, the error code can be used to signal
conditions from lower levels of the library to be handled by higher
levels of the library. For example, in a transaction we might
legitimately write an empty reftable file, but in that case, we want to
shortcut the transaction.
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
