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    Debugger: any way to breakpoint after several loop iterations?

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    • mzimmers
      mzimmers last edited by

      I hope this makes sense. I have a program that has nested loops, which would make stepping through very cumbersome. I'd like to be able to put a breakpoint somewhere in the middle of the outer loop. For example, if it runs 64 times, I'd like it to break after, say, 32 iterations, and then step through it.

      Is there some kind of conditional break I can put on the loop index, like "break with I > 32"? Any other techniques would be appreciated, too.

      Thanks.

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      • T
        tobias.hunger last edited by

        Yes, most debuggers support this. Check the documentation of your preferred debugger.

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        • mzimmers
          mzimmers last edited by

          Hi, Tobias –

          I just use gdb, and I use it entirely through the Creator interface. Assuming I find the gdb command for this, how do I access it through Creator?

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          • T
            tobias.hunger last edited by

            Just enter it into the top left area of the debugger mode (not 100% sure that is the right area, I have reordered stuff in my debug mode:-). You can interact with gdb normally there. Ctrl-Return will pass the command on to the debugger.

            Of course you could also use the "condition" field in the breakpoint configuration window (Right click on the breakpoint and choose "edit breakpoint" or something, sorry, I have no creator handy right now to look up the exact terms).

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            • mzimmers
              mzimmers last edited by

              I like the second suggestion much better. There's also an "ignore count" that I can use to do the same thing, more or less.

              What is the format for a valid condition? I tried "i < 10" (i is the index of the loop where the break is) but it doesn't stop.

              Thanks.

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              • T
                tobias.hunger last edited by

                No idea, I never used it:-) My guess is that it is passed directly to GDB, so it should be in whichever format GDB expects the condition.

                If you have questions on the debugger you better ask on the Qt Creator mailing list: The guys doing the debugger do hang out there but only very rarely read this forum.

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                • mzimmers
                  mzimmers last edited by

                  Hey, Tobias -

                  I've obviated the original problem for now, but I'd like to know more about this:

                  Just enter it into the top left area of the debugger mode (not 100% sure that is the right area, I have reordered stuff in my debug mode:-). You can interact with gdb normally there. Ctrl-Return will pass the command on to the debugger.

                  My debugger window doesn't show any place for entering something to pass to the debugger. Can you tell me where this "lives?"

                  Thanks.

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                  • T
                    tobias.hunger last edited by

                    The "debugger log" has the input area: It is the left one of the two text areas the log contains. It has a line edit labeled "Command".

                    Press Ctrl-Enter to actually send the input on to the debugger.

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                    • mzimmers
                      mzimmers last edited by

                      Hmm...OK, all I have is two bare text areas. No labels, nothing in them except text that appears to be going to/coming from the debugger. The left area seems to contain commands, preceded by numbers, like this:

                      bq. 1show version
                      2set print static-members off
                      3set breakpoint pending on
                      4set print elements 10000
                      5set overload-resolution off
                      6handle SIGSEGV nopass stop print
                      7set unwindonsignal on
                      8set width 0
                      9set height 0
                      10-interpreter-exec console "maintenance set internal-warning quit no"

                      But, typing in there and hitting ctrl-enter doesn't seem to do anything.

                      Come to think of it, I'm not sure where the commands in the left area are coming from.

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                      • mzimmers
                        mzimmers last edited by

                        If anyone can help me figure out where the debugger input area is, I'd appreciate it. Here's a picture of my Qt window in debugging mode:

                        !http://www.scopedin.com/images/qt.jpg(Qt window)!

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                        • T
                          tobias.hunger last edited by

                          Hmmm... my creator has a input line beneath the top left of the aceas (the one with the 36-gdb-exit) to input commands in. IIRC that was added to make it more discoverable that you can actually send commands to the debugger which used to work before IIRC.

                          Try typing into the top-left area and hitting Ctrl-Return.

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                          • mzimmers
                            mzimmers last edited by

                            I'm pretty sure it won't accept anything, but I'll try. I'm a bit embarrassed to say, however, that I don't know how to use GDB directly, so I don't know what to type in there. What do you suggest?

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                            • T
                              tobias.hunger last edited by

                              "google helps":http://www.lmgtfy.com/?q=gdb+manual...

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                              • mzimmers
                                mzimmers last edited by

                                OK, I downloaded the manual (585 pages!) and tried a simple break command. Nothing. It echoed my input (including the line-break) in the left window, but nothing in the right window and the break didn't take.

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                                • F
                                  Felix last edited by

                                  you could just add an @if(i > 32) { qDebug() << "32";}@ in the loop and make a regular breakpoint in the if statement

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                                  • ?
                                    Guest last edited by

                                    Mmm.... my approach to this would be using DDD (data display debugger? or sth like it) as an interface to GDB, then setting some breakpoints...

                                    --

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