Question

I am using Qsettings for non gui products to store its settings into xml files. This is written as a library which gets used in C, C++ programs. There will be 1 xml file file for each product. Each product might have more than one sub products and they are written into xml by subproduct grouping as follows –

File: “product1.xml”

<product1>
    <subproduct1>
       <settings1>..</settings1>
       ....
       <settingsn>..</settingsn>
    </subproduct1>
    ...
    <subproductn>
       <settings1>..</settings1>
       ....
       <settingsn>..</settingsn>
    </subproductn>

 </product1>

File: productn.xml

<productn>
   <subproduct1>
       <settings1>..</settings1>
       ....
       <settingsn>..</settingsn>
   </subproduct1>
   ...
   <subproductn>
       <settings1>..</settings1>
       ....
       <settingsn>..</settingsn>
   </subproductn>

 </productn>

The code in one process does the following –

settings = new QSettings("product1.xml", XmlFormat);
settings.setValue("settings1",<value>)
sleep(20);
settings.setValue("settings2", <value2>)
settings.sync();

When the first process goes to sleep, I start another process which does the following –

settings = new QSettings("product1.xml", XmlFormat);
settings.remove("settings1")
settings.setValue("settings3", <value3>)
settings.sync();

I would expect the settings1 to go away from product1.xml file but it still persist in the file – product1.xml at the end of above two process. I am not using QCoreApplication(..) in my settings library. Please point issues if there is anything wrong in the above design.

Answer 1

This is kind of an odd thing that you’re doing, but one thing to note is that the sync() call is what actually writes the file to disk. In this case if you want your second process to actually see the changes you’ve made, then you’ll need to call sync() before your second process accesses the file in order to guarantee that it will actually see your modifications. Thus I would try putting a settings.sync() call right before your sleep(20)