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QRegularExpression: do not mark as dirty on no-op setters

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Quite some code in Qt takes a copy of a QRegularExpression and then
changes something on it (e.g. the case sensitivity) based on some
other criteria:

  QRegularExpression copy = orig;
  if (cond)
    copy.setPatternOptions(copy.patternOptions() | CaseInsensitive);
  use(copy);

This pattern can be found in QAIM, QString-related classes, and so on.
The "problem" is that if the attempted modification is a no-op, we'd
still invalidate the copy object (by detaching). Even if no detaches
are involved, setting the same pattern or options on a QRE object
shouldn't require a relatively expensive pattern recompile.

In summary: don't detach/mark a QRE object as dirty if a setter didn't
actually do a modification.

Change-Id: Iae0ab4a5e443e7285a83d3d7e0f1dcfd66e8d51d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Giuseppe D'Angelo 2021-11-15 18:03:09 +01:00
parent ab67a6b126
commit 78a8e561b2
1 changed files with 4 additions and 0 deletions
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4
src/corelib/text/qregularexpression.cpp
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@ -1452,6 +1452,8 @@ QString QRegularExpression::pattern() const
*/
void QRegularExpression::setPattern(const QString &pattern)
{
if (d->pattern == pattern)
return;
d.detach();
d->isDirty = true;
d->pattern = pattern;
@ -1475,6 +1477,8 @@ QRegularExpression::PatternOptions QRegularExpression::patternOptions() const
*/
void QRegularExpression::setPatternOptions(PatternOptions options)
{
if (d->patternOptions == options)
return;
d.detach();
d->isDirty = true;
d->patternOptions = options;