How to redirect printf to QTextEdit?

[stampede]

for example, you can put this in .pro file:

build_pass:CONFIG(debug, debug|release) {
    DEFINES += <symbols you want to be defined only in debug build>
}

build_pass:CONFIG(debug, debug|release) {
    DEFINES += <symbols you want to be defined only in debug build>
}

To copy to clipboard, switch view to plain text mode 

so in your case DEFINES += DEBUG should be ok. Of course, this is all true under assumption that you can rebuild this library when compiling your project.