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QDebug "breaks" outputting a char with value 0?



  • Care to guess what would the output of this code be?

    @ char c = 0;
    for (int i = 0; i < 4; ++i) qDebug() << c << i << endl;@

    A hint - there is no output... as of why, it will be nice if someone briefly explains the internals of qDebug and what is the reason for this behavior...


  • Lifetime Qt Champion

    Hi,

    Just a quick thinking: c becomes the ascii character 0 which is invisible ?



  • Yes, if you use std::cout or QTextStream you will get an invisible character for c, but you will also get i and endl, while with qDebug the entire chain is terminated when the 0 char is reached so an invisible character is not being output, nor any of the stuff that follows.



  • First, QTextStream is used to generate a QString.
    Then, this string get output by following line.

    @
    fprintf(stderr, "%s", logMessage.toLocal8Bit().constData())
    @

    Consider that the first Char of the logMessage is '\0', so the length of the C string const char * will be zero. Though the length of the QString is not zero.


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