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Allow QHash randomization to be disabled by environment variable

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The new randomization of QHash is enabled by default. There may be cases
where you need deterministic behavior, e.g. for debugging or regression
testing. This patch disables randomization if QT_HASH_SEED is defined.

Change-Id: Idfad55ea7aba830add0a36334f0f763c62fdce13
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
This commit is contained in:
aavit 2012-05-22 10:59:17 +02:00 committed by Qt by Nokia
parent f604fd8ff4
commit b5a11a7be5
1 changed files with 11 additions and 0 deletions
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11
src/corelib/tools/qhash.cpp
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@ -158,6 +158,10 @@ uint qHash(const QLatin1String &key, uint seed)
*/ */
static uint qt_create_qhash_seed() static uint qt_create_qhash_seed()
{ {
QByteArray envSeed = qgetenv("QT_HASH_SEED");
if (!envSeed.isNull())
return envSeed.toUInt();
uint seed = 0; uint seed = 0;
#ifdef Q_OS_UNIX #ifdef Q_OS_UNIX
@ -866,6 +870,13 @@ void QHashData::checkSanity()
process, and then passed by QHash as the second argument of the process, and then passed by QHash as the second argument of the
two-arguments overload of the qHash() function. two-arguments overload of the qHash() function.
This randomization of QHash is enabled by default. Even though programs
should never depend on a particular QHash ordering, there may be situations
where you temporarily need deterministic behavior, e.g. for debugging or
regression testing. To disable the randomization, define the environment
variable \c QT_HASH_SEED. The contents of that variable, interpreted as a
decimal value, will be used as the seed for qHash().
\sa QHashIterator, QMutableHashIterator, QMap, QSet \sa QHashIterator, QMutableHashIterator, QMap, QSet
*/ */