From fce2a17a9c38d99b4a96024418317c81d32f8e94 Mon Sep 17 00:00:00 2001
From: Thiago Macieira <thiago.macieira@intel.com>
Date: Sun, 9 Feb 2025 11:27:24 -0800
Subject: [PATCH] QLibraryInfo: use fewer QFileInfo in finding qt.conf

This is hot code, run early in the application's life, usually as a
result of the first qDebug() because QLoggingRegistry wants to find
qtlogging.ini. So let's not use QFileInfo, which allocates memory, just
to do string manipulation. These are always filesystem paths.

See commit d59e640c868f3db2d661970f3d34a22013d49053 for a similar change
in findConfiguration().

Change-Id: I012daf4a3aa2ebc2c5abfffd2ef7ceac1df2626d
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
(cherry picked from commit c74cba1117355a6312b1f0cc815efa4cdea4bbfa)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit 3d43223448b4d5c1828501de4ec23edb2edc64d7)
---
 src/corelib/global/qlibraryinfo.cpp | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/src/corelib/global/qlibraryinfo.cpp b/src/corelib/global/qlibraryinfo.cpp
index 5f6042be29d..f6164213b0e 100644
--- a/src/corelib/global/qlibraryinfo.cpp
+++ b/src/corelib/global/qlibraryinfo.cpp
@@ -14,7 +14,7 @@
 
 #include "qcoreapplication.h"
 
-#include "private/qglobal_p.h"
+#include "private/qfilesystementry_p.h"
 #include "archdetect.cpp"
 #include "qconfig.cpp"
 
@@ -122,11 +122,11 @@ static std::unique_ptr<QSettings> findConfiguration()
     }
 #endif
     if (QCoreApplication::instance()) {
-        QDir pwd(QCoreApplication::applicationDirPath());
-        qtconfig = pwd.filePath(u"qt" QT_STRINGIFY(QT_VERSION_MAJOR) ".conf"_s);
+        QString pwd = QCoreApplication::applicationDirPath();
+        qtconfig = pwd + u"/qt" QT_STRINGIFY(QT_VERSION_MAJOR) ".conf"_s;
         if (QFile::exists(qtconfig))
             return std::make_unique<QSettings>(qtconfig, QSettings::IniFormat);
-        qtconfig = pwd.filePath("qt.conf"_L1);
+        qtconfig = pwd + u"/qt.conf";
         if (QFile::exists(qtconfig))
             return std::make_unique<QSettings>(qtconfig, QSettings::IniFormat);
     }
@@ -604,22 +604,26 @@ static QVariant libraryPathToValue(QLibraryInfo::LibraryPath loc)
 QStringList QLibraryInfoPrivate::paths(QLibraryInfo::LibraryPath p,
                                        UsageMode usageMode)
 {
+    using FromInternalPath = QFileSystemEntry::FromInternalPath;
     const QLibraryInfo::LibraryPath loc = p;
     QList<QString> ret;
     bool fromConf = false;
+    bool pathsAreAbsolute = true;
 #if QT_CONFIG(settings)
     if (havePaths()) {
         fromConf = true;
 
         QVariant value = libraryPathToValue(loc);
         if (value.isValid()) {
-
             if (auto *asList = get_if<QList<QString>>(&value))
                 ret = std::move(*asList);
             else
                 ret = QList<QString>({ std::move(value).toString()});
-            for (qsizetype i = 0, end = ret.size(); i < end; ++i)
+            for (qsizetype i = 0, end = ret.size(); i < end; ++i) {
                 ret[i] = normalizePath(ret[i]);
+                pathsAreAbsolute = pathsAreAbsolute
+                    && QFileSystemEntry(ret[i], FromInternalPath{}).isAbsolute();
+            }
         }
     }
 #endif // settings
@@ -640,10 +644,13 @@ QStringList QLibraryInfoPrivate::paths(QLibraryInfo::LibraryPath p,
             noConfResult = QString::fromLocal8Bit(path);
 #endif
         }
-        if (!noConfResult.isEmpty())
+        if (!noConfResult.isEmpty()) {
+            pathsAreAbsolute = pathsAreAbsolute
+                && QFileSystemEntry(noConfResult, FromInternalPath{}).isAbsolute();
             ret.push_back(std::move(noConfResult));
+        }
     }
-    if (ret.isEmpty())
+    if (ret.isEmpty() || pathsAreAbsolute)
         return ret;
 
     QString baseDir;
@@ -654,7 +661,7 @@ QStringList QLibraryInfoPrivate::paths(QLibraryInfo::LibraryPath p,
         baseDir = QLibraryInfoPrivate::path(QLibraryInfo::PrefixPath, usageMode);
     }
     for (qsizetype i = 0, end = ret.size(); i < end; ++i)
-        if (QDir::isRelativePath(ret[i]))
+        if (QFileSystemEntry(ret[i], FromInternalPath{}).isRelative())
             ret[i] = QDir::cleanPath(baseDir + u'/' +  std::move(ret[i]));
     return ret;
 }