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Maniphest T13554

Undefined offset exception in "PhutilProseDifferenceEngine::stitchPieces()"
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Description

See PHI1821. Likely after D21044, prose diffs may attempt to access an undefined index when stitching corpus components together. This may be similar to D21295.

Stack trace:

[2020-07-22 10:34:10] EXCEPTION: (PhutilProxyException) Error while executing Task ID 1618768. {>} (RuntimeException) Undefined offset: 1 at [<arcanist>/src/error/PhutilErrorHandler.php:258]
arcanist(head=stable, ref.master=3b6b523c2b23, ref.stable=2565cc7b4d1d), libcore(), phabricator(head=stable, ref.stable=2710a1e7aa42), services(head=stable, ref.master=772620edd80c, ref.stable=911b948c8e1f)
  #0 <#2> PhutilErrorHandler::handleError(integer, string, string, integer, array) called at [<phabricator>/src/infrastructure/diff/prose/PhutilProseDifferenceEngine.php:153]
  #1 <#2> PhutilProseDifferenceEngine::stitchPieces(array, integer) called at [<phabricator>/src/infrastructure/diff/prose/PhutilProseDifferenceEngine.php:132]
  #2 <#2> PhutilProseDifferenceEngine::splitCorpus(string, integer) called at [<phabricator>/src/infrastructure/diff/prose/PhutilProseDifferenceEngine.php:10]
  #3 <#2> PhutilProseDifferenceEngine::buildDiff(string, string, integer) called at [<phabricator>/src/infrastructure/diff/prose/PhutilProseDifferenceEngine.php:6]
  #4 <#2> PhutilProseDifferenceEngine::getDiff(string, string) called at [<phabricator>/src/applications/transactions/view/PhabricatorApplicationTransactionDetailView.php:170]
  #5 <#2> PhabricatorApplicationTransactionDetailView::buildDiff() called at [<phabricator>/src/applications/transactions/view/PhabricatorApplicationTransactionDetailView.php:19]
  #6 <#2> PhabricatorApplicationTransactionDetailView::renderForMail() called at [<phabricator>/src/applications/transactions/storage/PhabricatorApplicationTransaction.php:1460]
  #7 <#2> PhabricatorApplicationTransaction::renderChangeDetailsForMail(PhabricatorUser) called at [<phabricator>/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:3629]
  #8 <#2> PhabricatorApplicationTransactionEditor::addHeadersAndCommentsToMailBody(PhabricatorMetaMTAMailBody, array, string, string) called at [<phabricator>/src/applications/differential/editor/DifferentialTransactionEditor.php:632]
  #9 <#2> DifferentialTransactionEditor::buildMailBody(DifferentialRevision, array) called at [<phabricator>/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:3166]
  #10 <#2> PhabricatorApplicationTransactionEditor::buildMailForTarget(DifferentialRevision, array, PhabricatorMailTarget) called at [<phabricator>/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:3109]
  #11 <#2> PhabricatorApplicationTransactionEditor::buildMailWithRecipients(DifferentialRevision, array, array, array, array) called at [<phabricator>/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:3052]
  #12 <#2> PhabricatorApplicationTransactionEditor::buildMail(DifferentialRevision, array) called at [<phabricator>/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:1494]
  #13 <#2> PhabricatorApplicationTransactionEditor::publishTransactions(DifferentialRevision, array) called at [<phabricator>/src/applications/transactions/worker/PhabricatorApplicationTransactionPublishWorker.php:21]
  #14 <#2> PhabricatorApplicationTransactionPublishWorker::doWork() called at [<phabricator>/src/infrastructure/daemon/workers/PhabricatorWorker.php:124]
  #15 <#2> PhabricatorWorker::executeTask() called at [<phabricator>/src/infrastructure/daemon/workers/storage/PhabricatorWorkerActiveTask.php:159]
  #16 <#2> PhabricatorWorkerActiveTask::executeTask() called at [<phabricator>/src/infrastructure/daemon/workers/PhabricatorTaskmasterDaemon.php:22]
  #17 PhabricatorTaskmasterDaemon::run() called at [<phabricator>/src/infrastructure/daemon/PhutilDaemon.php:219]
  #18 PhutilDaemon::execute() called at [<phabricator>/scripts/daemon/exec/exec_daemon.php:131]

Revisions and Commits

rP Phabricator
D21422rPfcb75d0503c6 Fix an issue where prose diffing may fail after hitting the PCRE backtracking…

Related Objects

Event Timeline

epriestley triaged this task as Low priority.Jul 23 2020, 1:41 PM
epriestley created this task.
Herald added a subscriber: amckinley. · View Herald TranscriptJul 23 2020, 1:41 PM
epriestley added a comment.Jul 23 2020, 2:36 PM

This is a PCRE backtracking issue. It reproduces on an input corpus of length 3,277 bytes with only "x", " " (space), and "\n" (newline) characters, and disappears if I increase pcre.backtrack_limit.

The use of the ? in the second capturing expression means that we must backtrack for all spaces in the expression.

This test case reproduces it, depending on the value of pcre.backtrack_limit:

$this->assertProseParts(
  str_repeat('x ', 1024 * 1024),
  str_repeat('x ', 1024 * 1024),
  array(),
  pht('???'));

I think a single regular expression is not actually the best tool here.

epriestley added a revision: D21422: Fix an issue where prose diffing may fail after hitting the PCRE backtracking limit.Jul 23 2020, 2:40 PM
epriestley closed this task as Resolved by committing rPfcb75d0503c6: Fix an issue where prose diffing may fail after hitting the PCRE backtracking….Jul 23 2020, 2:46 PM
epriestley added a commit: rPfcb75d0503c6: Fix an issue where prose diffing may fail after hitting the PCRE backtracking….
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