QSettings: replace a QMap with a QList

The QMap<QString, QString> was only used to create a sorted,
unique list of keys. The associativeness was never used (the
value was always the null QString).

Better to use a QStringList instead and sort-unique the
whole thing at the end.

Saves ~1.6K in text size on Linux AMD64 GCC 4.9 release C++11
builds, and a tremendous amount of heap allocations.

Change-Id: Idf749dd8924b3894e436aa1cee0304002b898975
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/src/corelib/io/qsettings_mac.cpp b/src/corelib/io/qsettings_mac.cpp
index 083722869f..1ad198b990 100644
--- a/src/corelib/io/qsettings_mac.cpp
+++ b/src/corelib/io/qsettings_mac.cpp
@@ -491,7 +491,7 @@ bool QMacSettingsPrivate::get(const QString &key, QVariant *value) const
 
 QStringList QMacSettingsPrivate::children(const QString &prefix, ChildSpec spec) const
 {
-    QMap<QString, QString> result;
+    QStringList result;
     int startPos = prefix.size();
 
     for (int i = 0; i < numDomains; ++i) {
@@ -513,7 +513,10 @@ QStringList QMacSettingsPrivate::children(const QString &prefix, ChildSpec spec)
         if (!fallbacks)
             break;
     }
-    return result.keys();
+    std::sort(result.begin(), result.end());
+    result.erase(std::unique(result.begin(), result.end()),
+                 result.end());
+    return result;
 }
 
 void QMacSettingsPrivate::clear()