For regex escape sequences, just test directly for the relevant ASCII
characters rather than using locale-sensitive character
classification.
This fixes an assertion failure when a locale considers a non-ASCII
character, such as "൧", to be a digit.
Reported-by: Richard Guo
Discussion: https://postgr.es/m/CAMbWs49Q6UoKGeT8pBkMtJGJd+16CBFZaaWUk9Du+2ERE5g_YA@mail.gmail.com
Backpatch-through: 11
SplitToVariants() in the ispell code, lseg_inside_poly() in geo_ops.c,
and regex_selectivity_sub() in selectivity estimation could recurse
until stack overflow; fix by adding check_stack_depth() calls.
So could next() in the regex compiler, but that case is better fixed by
converting its tail recursion to a loop. (We probably get better code
that way too, since next() can now be inlined into its sole caller.)
There remains a reachable stack overrun in the Turkish stemmer, but
we'll need some advice from the Snowball people about how to fix that.
Per report from Egor Chindyaskin and Alexander Lakhin. These mistakes
are old, so back-patch to all supported branches.
Richard Guo and Tom Lane
Discussion: https://postgr.es/m/1661334672.728714027@f473.i.mail.ru
If search_start is greater than the length of the string, we should just
return REG_NOMATCH immediately. (Note that the equality case should
*not* be rejected, since the pattern might be able to match zero
characters.) This guards various internal assumptions that the min of a
range of string positions is not more than the max. Violation of those
assumptions could allow an attempt to fetch string[search_start-1],
possibly causing a crash.
Jaime Casanova pointed out that this situation is reachable with the
new regexp_xxx functions that accept a user-specified start position.
I don't believe it's reachable via any in-core call site in v14 and
below. However, extensions could possibly call pg_regexec with an
out-of-range search_start, so let's back-patch the fix anyway.
Discussion: https://postgr.es/m/20210911180357.GA6870@ahch-to
Second thoughts about commit 824bf7190: we apply makesearch() to
an NFA after having determined whether it is a MATCHALL pattern.
Prepending ".*" doesn't make it non-MATCHALL, but it does change the
maximum possible match length, and makesearch() failed to update that.
This has no ill effects given the stylized usage of search NFAs, but
it seems like it's better to keep the data structure consistent. In
particular, fixing this allows more honest handling of the MATCHALL
check in matchuntil(): we can now assert that maxmatchall is infinity,
instead of lamely assuming that it should act that way.
In passing, improve the code in dump[c]nfa so that infinite maxmatchall
is printed as "inf" not a magic number.
Regexps like "(.){0}...\1" drew an "invalid backreference number".
That's not unreasonable on its face, since the capture group will
never be matched if it's iterated zero times. However, other engines
such as Perl's don't complain about this, nor do we throw an error for
related cases such as "(.)|\1", even though that backref can never
succeed either. Also, if the zero-iterations case happens at runtime
rather than compile time --- say, "(x)*...\1" when there's no "x" to
be found --- that's not an error, we just deem the backref to not
match. Making this even less defensible, no error was thrown for
nested cases such as "((.)){0}...\2"; and to add insult to injury,
those cases could result in assertion failures instead. (It seems
that nothing especially bad happened in non-assert builds, though.)
Let's just fix it so that no error is thrown and instead the backref
is deemed to never match, so that compile-time detection of no
iterations behaves the same as run-time detection.
Per report from Mark Dilger. This appears to be an aboriginal error
in Spencer's library, so back-patch to all supported versions.
Pre-v14, it turns out to also be necessary to back-patch one aspect of
commits cb76fbd7e/00116dee5, namely to create capture-node subREs with
the begin/end states of their subexpressions, not the current lp/rp
of the outer parseqatom invocation. Otherwise delsub complains that
we're trying to disconnect a state from itself. This is a bit scary
but code examination shows that it's safe: in the pre-v14 code, if we
want to wrap iteration around the subexpression, the first thing we do
is overwrite the atom's begin/end fields with new states. So the
bogus values didn't survive long enough to be used for anything, except
if no iteration is required, in which case it doesn't matter.
Discussion: https://postgr.es/m/A099E4A8-4377-4C64-A98C-3DEDDC075502@enterprisedb.com
The recursion in cdissect() was careless about clearing match data
for capturing parentheses after rejecting a partial match. This
could allow a later back-reference to succeed when by rights it
should fail for lack of a defined referent.
To fix, think a little more rigorously about what the contract
between different levels of cdissect's recursion needs to be.
With the right spec, we can fix this using fewer rather than more
resets of the match data; the key decision being that a failed
sub-match is now explicitly responsible for clearing any matches
it may have set.
There are enough other cross-checks and optimizations in the code
that it's not especially easy to exhibit this problem; usually, the
match will fail as-expected. Plus, regexps that are even potentially
vulnerable are most likely user errors, since there's just not much
point in writing a back-ref that doesn't always have a referent.
These facts perhaps explain why the issue hasn't been detected,
even though it's almost certainly a couple of decades old.
Discussion: https://postgr.es/m/151435.1629733387@sss.pgh.pa.us
After detecting a sub-match "dissect" failure (i.e., a backref match
failure) in the i'th sub-match of an iteration node, we should proceed
by adjusting the attempted length of the i'th submatch. As coded,
though, these functions changed the attempted length of the *last*
sub-match, and only after exhausting all possibilities for that would
they back up to adjust the next-to-last sub-match, and then the
second-from-last, etc; all of which is wasted effort, since only
changing the start or length of the i'th sub-match can possibly make
it succeed. This oversight creates the possibility for exponentially
bad performance. Fortunately the problem is masked in most cases by
optimizations or constraints applied elsewhere; which explains why
we'd not noticed it before. But it is possible to reach the problem
with fairly simple, if contrived, regexps.
Oversight in my commit 173e29aa5. That's pretty ancient now,
so back-patch to all supported branches.
Discussion: https://postgr.es/m/1808998.1629412269@sss.pgh.pa.us
I had committer's remorse almost immediately after pushing cb76fbd7e,
upon finding that removing capturing subexpressions' subREs from the
data structure broke my proposed patch for REG_NOSUB optimization.
Revert that data structure change. Instead, address the concern
about not changing capturing subREs' endpoints by not changing the
endpoints. We don't need to, because the point of that bit was just
to ensure that the atom has endpoints distinct from the outer state
pair that we're stringing the branch between. We already made
suitable states in the parenthesized-subexpression case, so the
additional ones were just useless overhead. This seems more
understandable than Spencer's original coding, and it ought to be
a shade faster too by saving a few state creations and arc changes.
(I actually see a couple percent improvement on Jacobson's web
corpus, though that's barely above the noise floor so I wouldn't
put much stock in that result.)
Also, fix the logic added by ea1268f63 to ensure that the subRE
recorded in v->subs[subno] is exactly the one with capno == subno.
Spencer's original coding recorded the child subRE of the capture
node, which is okay so far as having the right endpoint states is
concerned, but as of cb76fbd7e the capturing subRE itself always
has those endpoints too. I think the inconsistency is confusing
for the REG_NOSUB optimization.
As before, backpatch to v14.
Discussion: https://postgr.es/m/0203588E-E609-43AF-9F4F-902854231EE7@enterprisedb.com
Up to now, we remembered the definition of a capturing parenthesis
subexpression by storing a pointer to the associated subRE node.
That was okay before, because that subRE didn't get modified anymore
while parsing the rest of the regexp. However, in the wake of
commit ea1268f63, that's no longer true: the outer invocation of
parseqatom() feels free to scribble on that subRE. This seems to
work anyway, because the states we jam into the child atom in the
"prepare a general-purpose state skeleton" stanza aren't really
semantically different from the original endpoints of the child atom.
But that would be mighty easy to break, and it's definitely not how
things worked before.
Between this and the issue fixed in the prior commit, it seems best
to get rid of this dependence on subRE nodes entirely. We don't need
the whole child subRE for future backrefs, only its starting and ending
NFA states; so let's just store pointers to those.
Also, in the corner case where we make an extra subRE to handle
immediately-nested capturing parentheses, it seems like it'd be smart
to have the extra subRE have the same begin/end states as the original
child subRE does (s/s2 not lp/rp). I think that linking it from lp to
rp might actually be semantically wrong, though since Spencer's original
code did it that way, I'm not totally certain. Using s/s2 is certainly
not wrong, in any case.
Per report from Mark Dilger. Back-patch to v14 where the problematic
patches came in.
Discussion: https://postgr.es/m/0203588E-E609-43AF-9F4F-902854231EE7@enterprisedb.com
Commit cebc1d34e taught parseqatom() to optimize cases where a branch
contains only one, "messy", atom by getting rid of excess subRE nodes.
The way we really should do that is to keep the subRE built for the
"messy" child atom; but to avoid changing parseqatom's nominal API,
I made it delete that node after copying its fields to the outer subRE
made by parsebranch(). It seems that that actually worked at the time;
but it became dangerous after ea1268f63, because that later commit
allowed the lower invocation of parse() to return a subRE that was also
pointed to by some v->subs[] entry. This meant we could wind up with a
dangling pointer in v->subs[], allowing a later backref to misbehave,
but only if that subRE struct had been reused in between. So the damage
seems confined to cases like '((...))...(...\2'.
To fix, do what I should have done before and modify parseqatom's API
to make it possible for it to remove the caller's subRE instead of the
callee's. That's safer because we know that subRE isn't complete yet,
so noplace else will have a pointer to it.
Per report from Mark Dilger. Back-patch to v14 where the problematic
patches came in.
Discussion: https://postgr.es/m/0203588E-E609-43AF-9F4F-902854231EE7@enterprisedb.com
Commit 824bf7190 introduced a new search of the NFAs generated by
regex compilation. I failed to think hard about the performance
characteristics of that search, with the predictable outcome
that it's bad: weird regexes can trigger exponential search time.
Worse, there's no check-for-interrupt in that code, so you can't
even cancel the query if this happens.
Fix by introducing memo-ization of the search results, so that any one
NFA state need be examined in detail just once. This potentially uses
a lot of memory, but we can bound the memory usage by putting a limit
on the number of states for which we'll try to prove match-all-ness.
That is sane because we already have a limit (DUPINF) on the maximum
finite string length that a matchall regex can match; and patterns
that involve much more than DUPINF states would probably exceed that
limit anyway.
Also, rearrange the logic so that we check the basic is-the-graph-
all-RAINBOW-arcs property before we start the recursive search to
determine path lengths. This will ensure that we fall out quickly
whenever the NFA couldn't possibly be matchall.
Also stick in a check-for-interrupt, just in case these measures
don't completely eliminate the risk of slowness.
Discussion: https://postgr.es/m/3483895.1619898362@sss.pgh.pa.us
Coverity is still unhappy after commit 190c79884, and after looking
closer I think it might be onto something. The callers of newdfa()
typically drop out if v->err has been set nonzero, which newdfa()
is faithfully doing if it fails. However, what if v->err was already
nonzero before we entered newdfa()? Then newdfa() could succeed and
the caller would promptly leak its result.
I don't think this scenario can actually happen, but the predicate
"v->err is always zero when newdfa() is called" seems difficult to be
entirely sure of; there's a good deal of code that potentially could
get that wrong.
It seems better to adjust the callers to directly check for a null
result instead of relying on ISERR() tests. This is slightly cheaper
than the previous coding anyway.
Lacking evidence that there's any real bug, no back-patch.
This extends the changes made in commit cebc1d34e, teaching
parseqatom() to generate fewer or cheaper subre nodes in some edge
cases. The case of interest here is a quantified atom that is "messy"
only because it has greediness opposite to what preceded it (whereas
captures and backrefs are intrinsically messy). In this case we don't
need an iteration node, since we don't care where the sub-matches of
the quantifier are; and we might also not need a second concatenation
node. This seems of only marginal real-world use according to my
testing, but I wanted to get it in before wrapping up this series of
regex performance fixes.
Discussion: https://postgr.es/m/1340281.1613018383@sss.pgh.pa.us
In some cases, at the time that we're doing an NFA-based precheck
of whether a backref subexpression can match at a particular place
in the string, we already know which substring the referenced
subexpression matched. If so, we might as well forget about the NFA
and just compare the substring; this is faster and it gives an exact
rather than approximate answer.
In general, this optimization can help while we are prechecking within
the second child expression of a concat node, while the capture was
within the first child expression; then the substring was saved during
cdissect() of the first child and will be available to NFA checks done
while cdissect() recurses into the second child. It can help quite a
lot if the tree looks like
concat
/ \
capture concat
/ \
expensive stuff backref
as we will be able to avoid recursively dissecting the "expensive
stuff" before discovering that the backref isn't satisfied with a
particular midpoint that the lower concat node is testing. This
doesn't help if the concat tree is left-deep, as the capture node
won't get set soon enough (and it's hard to fix that without changing
the engine's match behavior). Fortunately, right-deep concat trees
are the common case.
Patch by me, reviewed by Joel Jacobson
Discussion: https://postgr.es/m/661609.1614560029@sss.pgh.pa.us
POSIX defines the behavior of back-references thus:
The back-reference expression '\n' shall match the same (possibly
empty) string of characters as was matched by a subexpression
enclosed between "\(" and "\)" preceding the '\n'.
As far as I can see, the back-reference is supposed to consider only
the data characters matched by the referenced subexpression. However,
because our engine copies the NFA constructed from the referenced
subexpression, it effectively enforces any constraints therein, too.
As an example, '(^.)\1' ought to match 'xx', or any other string
starting with two occurrences of the same character; but in our code
it does not, and indeed can't match anything, because the '^' anchor
constraint is included in the backref's copied NFA. If POSIX intended
that, you'd think they'd mention it. Perl for one doesn't act that
way, so it's hard to conclude that this isn't a bug.
Fix by modifying the backref's NFA immediately after it's copied from
the reference, replacing all constraint arcs by EMPTY arcs so that the
constraints are treated as automatically satisfied. This still allows
us to enforce matching rules that depend only on the data characters;
for example, in '(^\d+).*\1' the NFA matching step will still know
that the backref can only match strings of digits.
Perhaps surprisingly, this change does not affect the results of any
of a rather large corpus of real-world regexes. Nonetheless, I would
not consider back-patching it, since it's a clear compatibility break.
Patch by me, reviewed by Joel Jacobson
Discussion: https://postgr.es/m/661609.1614560029@sss.pgh.pa.us
The previous logic here created a separate pool of arcs for each
state, so that the out-arcs of each state were physically stored
within it. Perhaps this choice was driven by trying to not include
a "from" pointer within each arc; but Spencer gave up on that idea
long ago, and it's hard to see what the value is now. The approach
turns out to be fairly disastrous in terms of memory consumption,
though. In the first place, NFAs built by this engine seem to have
about 4 arcs per state on average, with a majority having only one
or two out-arcs. So pre-allocating 10 out-arcs for each state is
already cause for a factor of two or more bloat. Worse, the NFA
optimization phase moves arcs around with abandon. In a large NFA,
some of the states will have hundreds of out-arcs, so towards the
end of the optimization phase we have a significant number of states
whose arc pools have room for hundreds of arcs each, even though only
a few of those arcs are in use. We have seen real-world regexes in
which this effect bloats the memory requirement by 25X or even more.
Hence, get rid of the per-state arc pools in favor of a single arc
pool for the whole NFA, with variable-sized allocation batches
instead of always asking for 10 at a time. While we're at it,
let's batch the allocations of state structs too, to further reduce
the malloc traffic.
This incidentally allows moveouts() to be optimized in a similar
way to moveins(): when moving an arc to another state, it's now
valid to just re-link the same arc struct into a different outchain,
where before the code invariants required us to make a physically
new arc and then free the old one.
These changes reduce the regex compiler's typical space consumption
for average-size regexes by about a factor of two, and much more for
large or complicated regexes. In a large test set of real-world
regexes, we formerly had half a dozen cases that failed with "regular
expression too complex" due to exceeding the REG_MAX_COMPILE_SPACE
limit (about 150MB); we would have had to raise that limit to
something close to 400MB to make them work with the old code. Now,
none of those cases need more than 13MB to compile. Furthermore,
the test set is about 10% faster overall due to less malloc traffic.
Discussion: https://postgr.es/m/168861.1614298592@sss.pgh.pa.us
We aren't publishing this file as documentation, and it's been
much more haphazardly maintained than the real docs in func.sgml,
so let's just drop it. I think the only reason I included it in
commit 7bcc6d98f was that the Berkeley-era sources had had a man
page in this directory.
Discussion: https://postgr.es/m/4099447.1614186542@sss.pgh.pa.us
Newline is certainly not a digit, nor a word character, so it is
sensible that it should match these complemented character classes.
Previously, \D and \W acted that way by default, but in
newline-sensitive mode ('n' or 'p' flag) they did not match newlines.
This behavior was previously forced because explicit complemented
character classes don't match newlines in newline-sensitive mode;
but as of the previous commit that implementation constraint no
longer exists. It seems useful to change this because the primary
real-world use for newline-sensitive mode seems to be to match the
default behavior of other regex engines such as Perl and Javascript
... and their default behavior is that these match newlines.
The old behavior can be kept by writing an explicit complemented
character class, i.e. [^[:digit:]] or [^[:word:]]. (This means
that \D and \W are not exactly equivalent to those strings, but
they weren't anyway.)
Discussion: https://postgr.es/m/3220564.1613859619@sss.pgh.pa.us
The complement-class escapes \D, \S, \W are now allowed within
bracket expressions. There is no semantic difficulty with doing
that, but the rather hokey macro-expansion-based implementation
previously used here couldn't cope.
Also, invent "word" as an allowed character class name, thus "\w"
is now equivalent to "[[:word:]]" outside brackets, or "[:word:]"
within brackets. POSIX allows such implementation-specific
extensions, and the same name is used in e.g. bash.
One surprising compatibility issue this raises is that constructs
such as "[\w-_]" are now disallowed, as our documentation has always
said they should be: character classes can't be endpoints of a range.
Previously, because \w was just a macro for "[:alnum:]_", such a
construct was read as "[[:alnum:]_-_]", so it was accepted so long as
the character after "-" was numerically greater than or equal to "_".
Some implementation cleanup along the way:
* Remove the lexnest() hack, and in consequence clean up wordchrs()
to not interact with the lexer.
* Fix colorcomplement() to not be O(N^2) in the number of colors
involved.
* Get rid of useless-as-far-as-I-can-see calls of element()
on single-character character element names in brackpart().
element() always maps these to the character itself, and things
would be quite broken if it didn't --- should "[a]" match something
different than "a" does? Besides, the shortcut path in brackpart()
wasn't doing this anyway, making it even more inconsistent.
Discussion: https://postgr.es/m/2845172.1613674385@sss.pgh.pa.us
Discussion: https://postgr.es/m/3220564.1613859619@sss.pgh.pa.us
gcc 10 is smart enough to notice that control could reach this
"hasmatch[depth]" assignment with depth < 0, but not smart enough
to know that that would require a badly broken NFA graph. Change
the assert() to a plain runtime test to shut it up.
Per report from Andres Freund.
Discussion: https://postgr.es/m/20210223173437.b3ywijygsy6q42gq@alap3.anarazel.de
Coverity complained that functions in regexec.c might leak DFA
storage. It's wrong, but this logic is confusing enough that it's
not so surprising Coverity couldn't make sense of it. Rewrite
in hopes of making it more legible to humans as well as machines.
Previously, each pair of capturing parentheses gave rise to a separate
subre tree node, whose only function was to identify that we ought to
capture the match details for this particular sub-expression. In
most cases we don't really need that, since we can perfectly well
put a "capture this" annotation on the child node that does the real
matching work. As with the two preceding commits, the main value
of this is to avoid generating and optimizing an NFA for a tree node
that's not really pulling its weight.
The chosen data representation only allows one capture annotation
per subre node. In the legal-per-spec, but seemingly not very useful,
case where there are multiple capturing parens around the exact same
bit of the regex (i.e. "((xyz))"), wrap the child node in N-1 capture
nodes that act the same as before. We could work harder at that but
I'll refrain, pending some evidence that such cases are worth troubling
over.
In passing, improve the comments in regex.h to say what all the
different re_info bits mean. Some of them were pretty obvious
but others not so much, so reverse-engineer some documentation.
This is part of a patch series that in total reduces the regex engine's
runtime by about a factor of four on a large corpus of real-world regexes.
Patch by me, reviewed by Joel Jacobson
Discussion: https://postgr.es/m/1340281.1613018383@sss.pgh.pa.us
Instead of having left and right child links in subre structs,
have a single child link plus a sibling link. Multiple children
of a tree node are now reached by chasing the sibling chain.
The beneficiary of this is alternation tree nodes. A regular
expression with N (>1) branches is now represented by one alternation
node with N children, rather than a tree that includes N alternation
nodes as well as N children. While the old representation didn't
really cost anything extra at execution time, it was pretty horrid
for compilation purposes, because each of the alternation nodes had
its own NFA, which we were too stupid not to separately optimize.
(To make matters worse, all of those NFAs described the entire
alternation pattern, not just the portion of it that one might
expect from the tree structure.)
We continue to require concatenation nodes to have exactly two
children. This data structure is now prepared to support more,
but the executor's logic would need some careful redesign, and
it's not clear that a lot of benefit could be had.
This is part of a patch series that in total reduces the regex engine's
runtime by about a factor of four on a large corpus of real-world regexes.
Patch by me, reviewed by Joel Jacobson
Discussion: https://postgr.es/m/1340281.1613018383@sss.pgh.pa.us
The comment for parsebranch() claims that it avoids generating
unnecessary concatenation nodes in the "subre" tree, but it missed
some significant cases. Once we've decided that a given atom is
"messy" and can't be bundled with the preceding atom(s) of the
current regex branch, parseqatom() always generated two new concat
nodes, one to concat the messy atom to what follows it in the branch,
and an upper node to concatenate the preceding part of the branch
to that one. But one or both of these could be unnecessary, if the
messy atom is the first, last, or only one in the branch. Improve
the code to suppress such useless concat nodes, along with the
no-op child nodes representing empty chunks of a branch.
Reducing the number of subre tree nodes offers significant savings
not only at execution but during compilation, because each subre node
has its own NFA that has to be separately optimized. (Maybe someday
we'll figure out how to share the optimization work across multiple
tree nodes, but it doesn't look easy.) Eliminating upper tree nodes
is especially useful because they tend to have larger NFAs.
This is part of a patch series that in total reduces the regex engine's
runtime by about a factor of four on a large corpus of real-world regexes.
Patch by me, reviewed by Joel Jacobson
Discussion: https://postgr.es/m/1340281.1613018383@sss.pgh.pa.us
This builds on the previous "rainbow" patch to detect NFAs that will
match any string, though possibly with constraints on the string length.
This definition is chosen to match constructs such as ".*", ".+", and
".{1,100}". Recognizing such an NFA after the optimization pass is
fairly cheap, since we basically just have to verify that all arcs
are RAINBOW arcs and count the number of steps to the end state.
(Well, there's a bit of complication with pseudo-color arcs for string
boundary conditions, but not much.)
Once we have these markings, the regex executor functions longest(),
shortest(), and matchuntil() don't have to expend per-character work
to determine whether a given substring satisfies such an NFA; they
just need to check its length against the bounds. Since some matching
problems require O(N) invocations of these functions, we've reduced
the runtime for an N-character string from O(N^2) to O(N). Of course,
this is no help for non-matchall sub-patterns, but those usually have
constraints that allow us to avoid needing O(N) substring checks in the
first place. It's precisely the unconstrained "match-all" cases that
cause the most headaches.
This is part of a patch series that in total reduces the regex engine's
runtime by about a factor of four on a large corpus of real-world regexes.
Patch by me, reviewed by Joel Jacobson
Discussion: https://postgr.es/m/1340281.1613018383@sss.pgh.pa.us
Some regular expression constructs, most notably the "." match-anything
metacharacter, produce a sheaf of parallel NFA arcs covering all
possible colors (that is, character equivalence classes). We can make
a noticeable improvement in the space and time needed to process large
regexes by replacing such cases with a single arc bearing the special
color code "RAINBOW". This requires only minor additional complication
in places such as pull() and push().
Callers of pg_reg_getoutarcs() must now be prepared for the possibility
of seeing a RAINBOW arc. For the one known user, contrib/pg_trgm,
that's a net benefit since it cuts the number of arcs to be dealt with,
and the handling isn't any different than for other colors that contain
too many characters to be dealt with individually.
This is part of a patch series that in total reduces the regex engine's
runtime by about a factor of four on a large corpus of real-world regexes.
Patch by me, reviewed by Joel Jacobson
Discussion: https://postgr.es/m/1340281.1613018383@sss.pgh.pa.us
While poking at the regex code, I happened to notice that the bug
squashed in commit afcc8772e had a sibling: next() failed to return
a specific value associated with the '}' token for a "\{m,n\}"
quantifier when parsing in basic RE mode. Again, this could result
in treating the quantifier as non-greedy, which it never should be in
basic mode. For that to happen, the last character before "\}" that
sets "nextvalue" would have to set it to zero, or it'd have to have
accidentally been zero from the start. The failure can be provoked
repeatably with, for example, a bound ending in digit "0".
Like the previous patch, back-patch all the way.
Push some hopefully-uncontroversial bits extracted from an upcoming
patch series, to remove non-relevant clutter from the main patches.
In compact(), return immediately after setting REG_ASSERT error;
continuing the loop would just lead to assertion failure below.
(Ask me how I know.)
In parseqatom(), remove assertion that moresubs() did its job.
When moresubs actually did its job, this is redundant with that
function's final assert; but when it failed on OOM, this is an
assertion crash. We could avoid the crash by adding a NOERR()
check before the assertion, but it seems better to subtract code
than add it. (Note that there's a NOERR exit a few lines further
down, and nothing else between here and there requires moresubs
to have succeeded. So we don't really need an extra error exit.)
This is a live bug in assert-enabled builds, but given the very
low likelihood of OOM in moresub's tiny allocation, I don't think
it's worth back-patching.
On the other hand, it seems worthwhile to add an assertion that
our intended v->subs[subno] target is still null by the time we
are ready to insert into it, since there's a recursion in between.
In pg_regexec, ensure we fflush any debug output on the way out,
and try to make MDEBUG messages more uniform and helpful. (In
particular, ensure that all of them are prefixed with the subre's
id number, so one can match up entry and exit reports.)
Add some test cases in test_regex to improve coverage of lookahead
and lookbehind constraints. Adding these now is mainly to establish
that this is indeed the existing behavior.
Discussion: https://postgr.es/m/1340281.1613018383@sss.pgh.pa.us
When REG_DEBUG is defined, ensure that an un-filled "struct cnfa"
is all-zeroes, not just that it has nstates == 0. This is mainly
so that looking at "struct subre" structs in gdb doesn't distract
one with a lot of garbage fields during regex compilation.
Adjust some places that print debug output to have suitable fflush
calls afterwards.
In passing, correct an erroneous ancient comment: the concatenation
subre-s created by parsebranch() have op == '.' not ','.
Noted while fooling around with some regex performance improvements.
brenext(), when parsing a '*' quantifier, forgot to return any "value"
for the token; per the equivalent case in next(), it should return
value 1 to indicate that greedy rather than non-greedy behavior is
wanted. The result is that the compiled regexp could behave like 'x*?'
rather than the intended 'x*', if we were unlucky enough to have
a zero in v->nextvalue at this point. That seems to happen with some
reliability if we have '.*' at the beginning of a BRE-mode regexp,
although that depends on the initial contents of a stack-allocated
struct, so it's not guaranteed to fail.
Found by Alexander Lakhin using valgrind testing. This bug seems
to be aboriginal in Spencer's code, so back-patch all the way.
Discussion: https://postgr.es/m/16814-6c5e3edd2bdf0d50@postgresql.org
The additional pain from level 4 is excessive for the gain.
Also revert all the source annotation changes to their original
wordings, to avoid back-patching pain.
Discussion: https://postgr.es/m/31166.1589378554@sss.pgh.pa.us
Use it at level 4, a bit more restrictive than the default level, and
tweak our commanding comments to FALLTHROUGH.
(However, leave zic.c alone, since it's external code; to avoid the
warnings that would appear there, change CFLAGS for that file in the
Makefile.)
Author: Julien Rouhaud <rjuju123@gmail.com>
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/20200412081825.qyo5vwwco3fv4gdo@nol
Discussion: https://postgr.es/m/flat/E1fDenm-0000C8-IJ@gemulon.postgresql.org
When maintaining or merging patches, one of the most common sources
for conflicts are the list of objects in makefiles. Especially when
the split across lines has been changed on both sides, which is
somewhat common due to attempting to stay below 80 columns, those
conflicts are unnecessarily laborious to resolve.
By splitting, and alphabetically sorting, OBJS style lines into one
object per line, conflicts should be less frequent, and easier to
resolve when they still occur.
Author: Andres Freund
Discussion: https://postgr.es/m/20191029200901.vww4idgcxv74cwes@alap3.anarazel.de
A bounded quantifier with m = n = 1 might be thought a no-op. But
according to our documentation (which traces back to Henry Spencer's
original man page) it still imposes greediness, or non-greediness in the
case of the non-greedy variant "{1,1}?", on whatever it's attached to.
This turns out not to work though, because parseqatom() optimizes away
the m = n = 1 case without regard for whether it's supposed to change
the greediness of the argument RE.
We can fix this by just not applying the optimization when the greediness
needs to change; the subsequent general cases handle it fine.
The three cases in which we can still apply the optimization are
(a) no quantifier, or quantifier does not impose a preference;
(b) atom has no greediness property, implying it cannot match a
variable amount of text anyway; or
(c) quantifier's greediness is same as atom's.
Note that in most cases where one of these applies, we'd have exited
earlier in the "not a messy case" fast path. I think it's now only
possible to get to the optimization when the atom involves capturing
parentheses or a non-top-level backref.
Back-patch to all supported branches. I'd ordinarily be hesitant to
put a subtle behavioral change into back branches, but in this case
it's very hard to see a reason why somebody would write "{1,1}?" unless
they're trying to get the documented change-of-greediness behavior.
Discussion: https://postgr.es/m/5bb27a41-350d-37bf-901e-9d26f5592dd0@charter.net
This adds a flag "deterministic" to collations. If that is false,
such a collation disables various optimizations that assume that
strings are equal only if they are byte-wise equal. That then allows
use cases such as case-insensitive or accent-insensitive comparisons
or handling of strings with different Unicode normal forms.
This functionality is only supported with the ICU provider. At least
glibc doesn't appear to have any locales that work in a
nondeterministic way, so it's not worth supporting this for the libc
provider.
The term "deterministic comparison" in this context is from Unicode
Technical Standard #10
(https://unicode.org/reports/tr10/#Deterministic_Comparison).
This patch makes changes in three areas:
- CREATE COLLATION DDL changes and system catalog changes to support
this new flag.
- Many executor nodes and auxiliary code are extended to track
collations. Previously, this code would just throw away collation
information, because the eventually-called user-defined functions
didn't use it since they only cared about equality, which didn't
need collation information.
- String data type functions that do equality comparisons and hashing
are changed to take the (non-)deterministic flag into account. For
comparison, this just means skipping various shortcuts and tie
breakers that use byte-wise comparison. For hashing, we first need
to convert the input string to a canonical "sort key" using the ICU
analogue of strxfrm().
Reviewed-by: Daniel Verite <daniel@manitou-mail.org>
Reviewed-by: Peter Geoghegan <pg@bowt.ie>
Discussion: https://www.postgresql.org/message-id/flat/1ccc668f-4cbc-0bef-af67-450b47cdfee7@2ndquadrant.com
Recent gcc can warn about switch-case fall throughs that are not
explicitly labeled as intentional. This seems like a good thing,
so clean up the warnings exposed thereby by labeling all such
cases with comments that gcc will recognize.
In files that already had one or more suitable comments, I generally
matched the existing style of those. Otherwise I went with
/* FALLTHROUGH */, which is one of the spellings approved at the
more-restrictive-than-default level -Wimplicit-fallthrough=4.
(At the default level you can also spell it /* FALL ?THRU */,
and it's not picky about case. What you can't do is include
additional text in the same comment, so some existing comments
containing versions of this aren't good enough.)
Testing with gcc 8.0.1 (Fedora 28's current version), I found that
I also had to put explicit "break"s after elog(ERROR) or ereport(ERROR);
apparently, for this purpose gcc doesn't recognize that those don't
return. That seems like possibly a gcc bug, but it's fine because
in most places we did that anyway; so this amounts to a visit from the
style police.
Discussion: https://postgr.es/m/15083.1525207729@sss.pgh.pa.us
Adjust commentary in regc_pg_locale.c to remove mention of the possibility
of not having <wctype.h> functions, since we no longer consider that.
Eliminate duplicate code in wparser_def.c by generalizing the p_iswhat
macro to take a parameter saying what to return for non-ASCII chars
in C locale. (That's not really a consequence of the
USE_WIDE_UPPER_LOWER-ectomy, but I noticed it while doing that.)
These functions are required by SUS v2, which is our minimum baseline
for Unix platforms, and are present on all interesting Windows versions
as well. Even our oldest buildfarm members have them. Thus, we were not
testing the "!USE_WIDE_UPPER_LOWER" code paths, which explains why the bug
fixed in commit e6023ee7f escaped detection. Per discussion, there seems
to be no more real-world value in maintaining this option. Hence, remove
the configure-time tests for wcstombs() and towlower(), remove the
USE_WIDE_UPPER_LOWER symbol, and remove all the !USE_WIDE_UPPER_LOWER code.
There's not actually all that much of the latter, but simplifying the #if
nests is a win in itself.
Discussion: https://postgr.es/m/20170921052928.GA188913@rfd.leadboat.com
Change pg_bsd_indent to follow upstream rules for placement of comments
to the right of code, and remove pgindent hack that caused comments
following #endif to not obey the general rule.
Commit e3860ffa4d wasn't actually using
the published version of pg_bsd_indent, but a hacked-up version that
tried to minimize the amount of movement of comments to the right of
code. The situation of interest is where such a comment has to be
moved to the right of its default placement at column 33 because there's
code there. BSD indent has always moved right in units of tab stops
in such cases --- but in the previous incarnation, indent was working
in 8-space tab stops, while now it knows we use 4-space tabs. So the
net result is that in about half the cases, such comments are placed
one tab stop left of before. This is better all around: it leaves
more room on the line for comment text, and it means that in such
cases the comment uniformly starts at the next 4-space tab stop after
the code, rather than sometimes one and sometimes two tabs after.
Also, ensure that comments following #endif are indented the same
as comments following other preprocessor commands such as #else.
That inconsistency turns out to have been self-inflicted damage
from a poorly-thought-through post-indent "fixup" in pgindent.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
The new indent version includes numerous fixes thanks to Piotr Stefaniak.
The main changes visible in this commit are:
* Nicer formatting of function-pointer declarations.
* No longer unexpectedly removes spaces in expressions using casts,
sizeof, or offsetof.
* No longer wants to add a space in "struct structname *varname", as
well as some similar cases for const- or volatile-qualified pointers.
* Declarations using PG_USED_FOR_ASSERTS_ONLY are formatted more nicely.
* Fixes bug where comments following declarations were sometimes placed
with no space separating them from the code.
* Fixes some odd decisions for comments following case labels.
* Fixes some cases where comments following code were indented to less
than the expected column 33.
On the less good side, it now tends to put more whitespace around typedef
names that are not listed in typedefs.list. This might encourage us to
put more effort into typedef name collection; it's not really a bug in
indent itself.
There are more changes coming after this round, having to do with comment
indentation and alignment of lines appearing within parentheses. I wanted
to limit the size of the diffs to something that could be reviewed without
one's eyes completely glazing over, so it seemed better to split up the
changes as much as practical.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
regexport.c thought it could just ignore LACON arcs, but the correct
behavior is to treat them as satisfiable while consuming zero input
(rather reminiscently of commit 9f1e642d5). Otherwise, the emitted
simplified-NFA representation may contain no paths leading from initial
to final state, which unsurprisingly confuses pg_trgm, as seen in
bug #14623 from Jeff Janes.
Since regexport's output representation has no concept of an arc that
consumes zero input, recurse internally to find the next normal arc(s)
after any LACON transitions. We'd be forced into changing that
representation if a LACON could be the last arc reaching the final
state, but fortunately the regex library never builds NFAs with such
a configuration, so there always is a next normal arc.
Back-patch to 9.3 where this logic was introduced.
Discussion: https://postgr.es/m/20170413180503.25948.94871@wrigleys.postgresql.org
Add a column collprovider to pg_collation that determines which library
provides the collation data. The existing choices are default and libc,
and this adds an icu choice, which uses the ICU4C library.
The pg_locale_t type is changed to a union that contains the
provider-specific locale handles. Users of locale information are
changed to look into that struct for the appropriate handle to use.
Also add a collversion column that records the version of the collation
when it is created, and check at run time whether it is still the same.
This detects potentially incompatible library upgrades that can corrupt
indexes and other structures. This is currently only supported by
ICU-provided collations.
initdb initializes the default collation set as before from the `locale
-a` output but also adds all available ICU locales with a "-x-icu"
appended.
Currently, ICU-provided collations can only be explicitly named
collations. The global database locales are still always libc-provided.
ICU support is enabled by configure --with-icu.
Reviewed-by: Thomas Munro <thomas.munro@enterprisedb.com>
Reviewed-by: Andreas Karlsson <andreas@proxel.se>
Although there are good reasons for our policy of including postgres.h
as the first #include in every .c file, never from .h files, there are
two places where it seems expedient to violate the policy because the
alternative is to modify externally-supplied .c files. (In the case
of the regexp library, the idea that it's externally-supplied is kind
of at odds with reality, but I haven't entirely given up hope that it
will become a standalone project some day.) Add some comments to make
it explicit that this is a policy violation and provide the reasoning.
In passing, move #include "miscadmin.h" out of regcomp.c and into
regcustom.h, which is where it should be if we're taking this reasoning
seriously at all.
Discussion: https://postgr.es/m/CAEepm=2zCoeq3QxVwhS5DFeUh=yU6z81pbWMgfOB8OzyiBwxzw@mail.gmail.com
Discussion: https://postgr.es/m/11634.1488932128@sss.pgh.pa.us
Jeff Davis
Tom Lane
Bruce Momjian
Alvaro Herrera
Andres Freund
Michael Paquier
Peter Eisentraut
Peter Eisentraut