Question

链接到Qt Bug报告：QTBUG-53313

从Qt 5.5迁移到Qt 5.6会出现QSettings的问题，它无法在系统范围内找到QSettings配置文件。在下面的main.cpp中，QSettings以各种方式初始化，然后查询其属性：

// File: main.cpp

#include <QApplication>
#include <QDebug>
#include <QSettings>
#include <QCoreApplication>

#define ASSUMED_SYSTEM_CONFIG "/etc/xdg/TheOrg/TheApp.conf"
#define ASSUMED_USER_CONFIG "/home/user/.config/TheOrg/TheApp.conf"

void print_info(const QSettings& settings, const char& use_case);

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QCoreApplication::setOrganizationName("TheOrg");
    QCoreApplication::setApplicationName("TheApp");

    QSettings settings_a;
    QSettings settings_b("TheOrg", "TheApp");
    QSettings settings_c(QSettings::SystemScope, "TheOrg", "TheApp");
    QSettings settings_d(QSettings::NativeFormat, QSettings::SystemScope, "TheOrg", "TheApp");

    print_info(settings_a, 'a');    
    print_info(settings_b, 'b');    
    print_info(settings_c, 'c');    
    print_info(settings_d, 'd');

    return a.exec();
}

void print_info(const QSettings& settings, const char& use_case)
{
    int value = settings.value("the_value").toInt();

    qDebug() << "Using case (" << use_case << ")";

    qDebug() << "The value is " << value;

    qDebug() << "Settings scope is: " << ((settings.scope() == QSettings::SystemScope) ? "System" : "User");
    qDebug() << "Settings organization is: " << settings.organizationName();
    qDebug() << "Settings application name is: " << settings.applicationName();
    qDebug() << "Settings fallbackEnabled is: " << settings.fallbacksEnabled();
    qDebug() << "Settings filename is: " << settings.fileName() << "\n";
}

系统上的 ASSUMED_USER_CONFIG 文件不存在。

系统上的 ASSUMED_SYSTEM_CONFIG 文件确实存在，其中包含：

the_value = 42

使用Qt 5.5编译，程序返回：

Using case ( a )
The value is  42
Settings scope is:  User
Settings organization is:  "TheOrg"
Settings application name is:  "TheApp"
Settings fallbackEnabled is:  true
Settings filename is:  "/home/user/.config/TheOrg/TheApp.conf" 

Using case ( b )
The value is  42
Settings scope is:  User
Settings organization is:  "TheOrg"
Settings application name is:  "TheApp"
Settings fallbackEnabled is:  true
Settings filename is:  "/home/user/.config/TheOrg/TheApp.conf" 

Using case ( c )
The value is  42
Settings scope is:  System
Settings organization is:  "TheOrg"
Settings application name is:  "TheApp"
Settings fallbackEnabled is:  true
Settings filename is:  "/etc/xdg/TheOrg/TheApp.conf" 

Using case ( d )
The value is  42
Settings scope is:  System
Settings organization is:  "TheOrg"
Settings application name is:  "TheApp"
Settings fallbackEnabled is:  true
Settings filename is:  "/etc/xdg/TheOrg/TheApp.conf"

使用Qt 5.6编译，程序返回：

Using case ( a )
The value is  0
Settings scope is:  User
Settings organization is:  "TheOrg"
Settings application name is:  "TheApp"
Settings fallbackEnabled is:  true
Settings filename is:  "/home/user/.config/TheOrg/TheApp.conf" 

Using case ( b )
The value is  0
Settings scope is:  User
Settings organization is:  "TheOrg"
Settings application name is:  "TheApp"
Settings fallbackEnabled is:  true
Settings filename is:  "/home/user/.config/TheOrg/TheApp.conf" 

Using case ( c )
The value is  0
Settings scope is:  System
Settings organization is:  "TheOrg"
Settings application name is:  "TheApp"
Settings fallbackEnabled is:  true
Settings filename is:  "/home/user/Qt5.6/5.6/gcc_64/etc/xdg/TheOrg/TheApp.conf" 

Using case ( d )
The value is  0
Settings scope is:  System
Settings organization is:  "TheOrg"
Settings application name is:  "TheApp"
Settings fallbackEnabled is:  true
Settings filename is:  "/home/user/Qt5.6/5.6/gcc_64/etc/xdg/TheOrg/TheApp.conf"

这里有一些问题：

使用Qt 5.5进行编译时，设置'文件名'将按预期为所有情况（a，b，c，d）构建。案例'a'和'b'是ASSUMED_SYSTEM_CONFIG文件的falling back，因为ASSUMED_USER_CONFIG文件不存在。因此，可以从设置文件中正确检索“the_value”。

然而，当使用Qt 5.6进行编译时，对于'c'和'd'的情况，设置'filename'似乎构造错误（正确的路径被附加到“/home/user/Qt5.6/5.6/ gcc_64" ）。因此，无法从设置文件中检索“the_value”。

我没有覆盖Qt Creator中的任何默认环境变量，Qt维护工具自动安装了Qt 5.6。我知道我可以使用环境变量XDG_CONFIG_HOME来设置QSettings :: SystemScope文件的绝对路径，但我认为不应该这样做。

要重述主要问题，如何在QSettings中使用ASSUMED_SYSTEM_CONFIG文件（即QSettings :: SystemScope）？

还有其他人反对这个吗？我在两台不同的机器上测试了它。

Answer 1

这是预编译的linux二进制文件的问题。如果从源代码编译Qt 5.6，可以通过使用标志'-sysconfdir = / etc'编译Qt来避免此问题。

如果这不是一个选项，您可以设置环境变量XDG_CONFIG_HOME。

This bug should now be fixed in the Qt 5.6.1 snapshot。

Unix Qt 5.6 QSettings找不到QSettings :: SystemScope配置文件

1 个答案: