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  • gdb: SIGTRAP on std::string::c_str() call

    - by sheepsimulator
    So I've been trying to use gdb to return the value of a string I have by calling > print <member variable name>.c_str() But everytime I do so, I get this: Program received signal SIGTRAP, Trace/breakpoint trap. <some address> in std::string::c_str() from /usr/lib/libstdc++.so.6 GDB remains in the frame where the signal was received. To change this behavior use "set unwindonsignal on" Evaluation of the expression containing the function (std::string::c_str() const) will be abandoned. Two questions: Why/how is the standard library throwing SIGTRAP? I checked basic_string.h and c_str() is defined as: const _CharT* c_str() const { return _M_data(); } I don't see any SIGTRAP-throwing here... is there a way to get around this SIGTRAP? How can I read the text value of the std::string out (without getting some crazy extension library) in gdb?

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  • What exactly does raw microphone data represent?

    - by esperantist
    I'm using PyAudio, a PortAudio wrapper for Python. I'm getting data from a microphone. Data which is represented by a continuous stream of bytes divided into chunks (of a size determined by me). I've tried to plot the signal, assuming the bytes represent the current signal amplitude, but I get an interesting image that I can't easily describe. ^^ It seems to be composed of two waves, one shifted from the other. What exactly do the particular bytes represent, and how does this change when I'm recording only one channel, instead of two? Any explanations, suggestions, code snippets, anything, very welcome! (I'm new at this.) Thanks!

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  • Boost signals and passing class method

    - by Ockonal
    Hello, I've defined some signal: typedef boost::signals2::signal<void (int temp)> SomeSig; typedef SomeSig::slot_type SomeSigType; I have some class: class SomeClass { SomeClass() { SomeSig.connect(&SomeClass::doMethod); } void doMethod(const SomeSig &slot); }; And got a lot of errors: error: ‘BOOST_PP_ENUM_SHIFTED_PARAMS_M’ was not declared in this scope error: ‘T’ was not declared in this scope error: a function call cannot appear in a constant-expression error: a function call cannot appear in a constant-expression error: template argument 1 is invalid error: ‘BOOST_SIGNALS2_MISC_STATEMENT’ has not been declared error: expected identifier before ‘~’ token error: expected ‘)’ before ‘~’ token error: expected ‘;’ before ‘~’ token

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  • PDF Encrypted, Hidden Watermark

    - by Dave Jarvis
    Background Using LaTeX to write a book. When a user purchases the book, the PDF will be generated automatically. Problem The PDF should have a watermark that includes the person's name and contact information. Question What software meets the following criteria: Applies encrypted, undetectable watermarks to a PDF Open Source Platform independent (Linux, Windows) Fast (marks a 200 page PDF in under 1 second) Batch processing (exclusively command-line driven) Collusion-attack resistant Non-fragile (e.g., PDF - EPS - PDF still contains the watermark) Well documented (shows example usages) Ideas & Resources Some thoughts and findings: Natural language processing (NLP) watermarks. Apply steganography on a randomly selected image. http://openstego.sourceforge.net/cmdline.html The problem with NLP is that grammatical errors can be introduced. The problem with steganography is that the images are sourced from an image cache, and so recreating that cache with watermarked images will impart a delay when generating the PDF (I could just delete one image from the cache, but that's not an elegant solution). Thank you!

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  • Checking status after wait()

    - by Helper Method
    After creating a child process and exiting it immediately (_exit()), I want to perform a wait and check the status. Now I wonder if in the 'else' branch of the if/else construct I also need to check for WIFSIGNALED. As far as I understand, if I perform a wait, a) an error could have occured (-1), the child could have terminated normally by an (exit() or _exit()), or it could have been terminated by a signal, so the check could be omitted, right? //remainder omitted int status; pid_t t_pid = wait(&status); if (t_pid == -1) { perror("wait"); exit(EXIT_FAILURE); } if (WIFEXITED(status)) { printf("child terminated normally, status = %d\n", WEXITSTATUS(status) ); } else { // <-- do it have to check for WIFSIGNALED() here? printf("child was terminated by a signal, signum = %d\n", WTERMSIG(status) ); }

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  • Can I make ungetc unblock a blocking fgetc call?

    - by Paul Beckingham
    I would like to stuff an 'A' character back into stdin using ungetc on receipt of SIGUSR1. Imagine that I have a good reason for doing this. When calling foo(), the blocking read in stdin is not interrupted by the ungetc call on receipt of the signal. While I didn't expect this to work as is, I wonder if there is a way to achieve this - does anyone have suggestions? void handler (int sig) { ungetc ('A', stdin); } void foo () { signal (SIGUSR1, handler); while ((key = fgetc (stdin)) != EOF) { ... } }

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  • Do I need to retain Sharepoint usage analysis log files

    - by dunxd
    Our Sharepoint installation currently has 30Gb of Usage Analysis Log file - these date back about six months. I have configured Sharepoint to do Usage Analysis Processing every night, so I am wondering whether I need to keep these files for so long. Sharepoint doesn't seem to clean up these files automatically - I think six months ago I had to clear out logs due to disk space issues. So my question is, do I need to retain these files in order to get decent usage analysis reports, or can I delete them as soon as the usage analysis processing has completed?

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  • Ubuntu can't install an older version of a package

    - by Trevor Newhook
    When I try to do an apt-get install, I keep getting an error: Depends: libgtk-3-common (= 3.4.1-0ubuntu1) but 3.4.2-0ubuntu0.4 is to be installed when I run sudo apt-get -f install, I get several dpkg: warning: files list file for package 'XXX' missing, assuming package has no files currently installed. then Preparing to replace libgtk-3-bin 3.4.1-0ubuntu1 (using .../libgtk-3-bin_3.4.2-0ubuntu0.4_i386.deb) ... Adding 'diversion of /usr/sbin/update-icon-caches to /usr/sbin/update-icon-caches.gtk2 by libgtk-3-bin' dpkg-divert: error: rename involves overwriting `/usr/sbin/update-icon-caches.gtk2' with different file `/usr/sbin/update-icon-caches', not allowed dpkg: error processing /var/cache/apt/archives/libgtk-3-bin_3.4.2-0ubuntu0.4_i386.deb (--unpack): subprocess new pre-installation script returned error exit status 2 Errors were encountered while processing: /var/cache/apt/archives/libgtk-3-bin_3.4.2-0ubuntu0.4_i386.deb E: Sub-process /usr/bin/dpkg returned an error code (1) I'm not sure why it's complaining about a newer version of a package, but any help would be appreciated

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  • Multiple Graphics cards - Non Multi-Display Setup

    - by Alan Thomas
    Is it possible for me to utilize the processing capabilities of multiple graphics cards, even if I'm only using one monitor? I recently bought a new AMD graphics card, fairly top of the line. I also have a two year old, decent nVidia card. They're obviously very different cards. I don't really mind for gaming because my current card can handle most games fine by itself. I'm concerned about video editing programs such as Adobe Premiere and After Effects. Would the system be able to utilize the power of both cards to, say, render a video? I have both drivers still installed on my machine. And because there is only one monitor connected to my current graphics card (AMD) the nVidia would be connected to no display. So I am wondering whether it would or could be utilized in some way to help in processing video. Thanks!

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  • update table in gtk

    - by ali
    I have window that contains a table on screen, now I want to attach a widget to that table I use gtk_table_attach(GTK_TABLE(table), label, ...) the function is correct and it runs without any error but table does not respond to that line I mean there is no change on my table, I think I need something to tell that table update it self but how? note= that line is inside a callback of a signal and I am sure that signal runs note2= I do not want to destroy window for that note3= I use gtk+ and pygtk note4= I am sure I attach that widget to a correct position ( it is free)

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  • How to make a quiet laptop?

    - by psihodelia
    Most modern laptops have very noisy fans. I am looking for a quiet laptop or a small stationary computer which has all its hardware built in a display. Most tasks will be PDF/docs processing, real-time audio processing, web-surfing and Skype video chats. Certainly, there is no any fan-less model today; but maybe some of the existed laptops do not switch on their fans so often or implement different solutions? For example, an iPad has no fan at all and it is fast enough for my needs, but it has no normal operating system, so I can't use it for anything but audio chats and web-surfing. Or maybe I can buy a laptop and tweak it to make it absolutely noiseless? Can you recommend any solution please?

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  • not able to install g++ and gcc on debian

    - by austin powers
    Hi , I want to use directadmin as my web control panel and it needs several packages like g++ , gcc and etc... as usuall I started to type apt-get install g++ and there problems start : dependecy error... then I tried to apt-get -f install and I got this error (Reading database ... 15140 files and directories currently installed.) Removing libc6-xen ... ldconfig: /etc/ld.so.conf.d/libc6-xen.conf:6: hwcap index 0 already defined as nosegneg dpkg: error processing libc6-xen (--remove): subprocess post-removal script returned error exit status 1 Errors were encountered while processing: libc6-xen E: Sub-process /usr/bin/dpkg returned an error code (1) what shoud I do? I want to install g++ and all of its dependencies due to using of directadmin I need it. regards.

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  • Vim: multi-file editing - having different makes in different splits

    - by gmatt
    I'm a recent vim convert (from fancy IDEs like eclipse.) I love the :make command in vim and use it extensively; however I also like to edit multiple projects (with separate makefiles.) So usually to edit more than one project I will do pushd project1 vim project1.cpp [suspend signal] pushd ../project2 vim project2.cpp and now I can switch between the two projects with ctrl+z i.e. suspend signal, and fg. When this becomes an issue is when I want to open one project in the context of another so I can do copy/pasting. So if instead in the above I do pushd project1 vim project1.cpp :vsp ../project2/project2.cpp I can edit both concurrently in the same vim process, however I can't effectively build one or the other with the :make command, it will only build project 1. Does anyone have some kind of scheme that gives them the best of both worlds: being able to edit concurrently while still being able to build multiple projects with the :make command all from the same vim process?

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  • Qt: Dragging a widget to scroll the widget's parent QScrollArea?

    - by samsonite
    I've got a long horizontal QLabel displaying a png (the image shows a signal/time graph). Under that, I've got a QTableWidget. Both of these are in a QScrollArea because I want them to stay vertically aligned (the cells in the table correspond with the signal seen directly above them). I'm trying to add a handler to the QLabel such that the user can use the picture itself to scroll the scrollarea, rather than having to use the scrollbar. Is there a tried-and-tested way to do this? Directly setting the scrollarea's sliderPosition inside the QLabel's dragMoveEvent doesn't seem smart, because when the scrollarea scrolls it also leads to another dragMoveEvent on the (moving) QLabel.

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  • cannot read but can write on serial port through Android Emulator

    - by Aad
    I am working on a program that is communicating with serial port over USB through Android emulator. emulator -qemu -serial /dev/ttyUSB0 The emulator is able to open the port and write into it. However, read is not happening. The program has a timeout for read maintained by a timer. The read happens in a separate 'read' thread. The main thread has a socketpair fd pair to signal the read-thread that the serial port is closed post timeout. In the read-thread, polling happens(poll() function call) over the 2 file-descriptors: one is serial port fd, the other is one of the socketpair. The board that I have connected to works fine with sending commands over 'cutecom' The poll never succeeds for serial port. However, poll succeeds for 'socketpair'ed fd and the thread ends on a close-signal sent from main-thread post timeout. Ouestions: Are there any special settings for read as even loop-back fails Are there differences between settings for read and write on a serial port?

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  • Python, Matplotlib, subplot: How to set the axis range?

    - by someone
    How can I set the y axis range of the second subplot to e.g. [0,1000] ? The FFT plot of my data (a column in a text file) results in a (inf.?) spike so that the actual data is not visible. pylab.ylim([0,1000]) has no effect, unfortunately. This is the whole script: # based on http://www.swharden.com/blog/2009-01-21-signal-filtering-with-python/ import numpy, scipy, pylab, random xs = [] rawsignal = [] with open("test.dat", 'r') as f: for line in f: if line[0] != '#' and len(line) > 0: xs.append( int( line.split()[0] ) ) rawsignal.append( int( line.split()[1] ) ) h, w = 3, 1 pylab.figure(figsize=(12,9)) pylab.subplots_adjust(hspace=.7) pylab.subplot(h,w,1) pylab.title("Signal") pylab.plot(xs,rawsignal) pylab.subplot(h,w,2) pylab.title("FFT") fft = scipy.fft(rawsignal) #~ pylab.axis([None,None,0,1000]) pylab.ylim([0,1000]) pylab.plot(abs(fft)) pylab.savefig("SIG.png",dpi=200) pylab.show() Other improvements are also appreciated!

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  • How to make a quiet laptop ? [closed]

    - by psihodelia
    Most modern laptops have very noisy fans. I am looking for a quiet laptop or a small stationary computer which has all its hardware built in a display. Most tasks will be pdf/docs processing, real-time audio processing, web-surfing and skype video chats. Certainly, there is no any fan-less model today; but maybe some of the existed laptops do not switch on their fans so often or implement different solutions? For example, an iPad has no fan at all and it is fast enough for my needs, but it has no normal operating system, so I can't use it for anything but audio chats and web-surfing. Or maybe I can buy a laptop and tweak it to make it absolutely noiseless? Can you recommend me any solution please? Thanks in advance!

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  • Win XP cannot connect (or see) my wifi network, but can see others

    - by Jorre
    since yesterday I have a strange wifi problem with my pc. I have a wireless linksys router setup that worked fine for many months, now since yesterday my pc won't connect to the wifi signal anymore. The strange thing is, my macbook pro still connects fine. SSID is broadcasting, but my windows XP doens't see it, I have all signal modes set to "auto". Windows XP sees all my neighbours wifi networks, so the wifi card isn't broken or anything. Any idea what can be wrong here?

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  • Django refresh page if change data by other user

    - by Fran Sobrino
    I have a test django app. In one page the test show the same question to all users. I'd like that when a user answers correctly, send a signal to other active user's browser to refresh to the next question. I have been learning about signals in django I learning work with them but I don't now how send the "refresh signal" to client browser. I think that it can do with a javascript code that check if a certain value (actual question) change and if change reload the page but I don't know this language and the information that I find was confused. Can anybody help me? Many Thanks.

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  • Does all the network card use the same frequency to send signals to wire?

    - by smwikipedia
    Hi, I am comparing my cable TV wire to my network wire. In a TV cable wire, different frequencies are used by different TV channels. And since a certain channel use a fixed frequency, I think the only left way to represent different signal is with the carrier wave's amplitude. But what about the network wire? For all the network card with the same type, do they also use different frequencies to send signals just like TV cable? I vaguely remember that they use frequency adjustment to represent signals. So the frequency should not be a fixed one. So how did all the network cards that sharing the same medium differentiate their own signal from others?

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  • threading.Event wait function not signaled when subclassing Process class

    - by user1313404
    For following code never gets past the wait function in run. I'm certain I'm doing something ridiculously stupid, but since I'm not smart enough to figure out what, I'm asking. Any help is appreciated. Here is the code: import threading import multiprocessing from multiprocessing import Process class SomeClass(Process): def __init__(self): Process.__init__(self) self.event = threading.Event() self.event.clear() def continueExec(self): print multiprocessing.current_process().name print self print "Set:" + str(self.event.is_set()) self.event.set() print "Set:" + str(self.event.is_set()) def run(self): print "I'm running with it" print multiprocessing.current_process().name self.event.wait() print "I'm further than I was" print multiprocessing.current_process().name self.event.clear() def main(): s_list = [] for t in range(3): s = SomeClass() print "s:" + str(s) s_list.append(s) s.start() raw_input("Press enter to send signal") for t in range(3): print "s_list["+str(t)+"]:" + str(s_list[t]) s_list[t].continueExec() raw_input("Press enter to send signal") for t in range(3): s_list[t].join() print "All Done" if __name__ == "__main__": main()

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  • Why is volatile not considered useful in multithreaded C or C++ programming?

    - by Michael E
    As demonstrated in this answer I recently posted, I seem to be confused about the utility (or lack thereof) of volatile in multi-threaded programming contexts. My understanding is this: any time a variable may be changed outside the flow of control of a piece of code accessing it, that variable should be declared to be volatile. Signal handlers, I/O registers, and variables modified by another thread all constitute such situations. So, if you have a global int foo, and foo is read by one thread and set atomically by another thread (probably using an appropriate machine instruction), the reading thread sees this situation in the same way it sees a variable tweaked by a signal handler or modified by an external hardware condition and thus foo should be declared volatile (or, for multithreaded situations, accessed with memory-fenced load, which is probably a better a solution). How and where am I wrong?

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  • Display CPU usage separately (without root privileges)

    - by synaptik
    I need to display the CPU usage for each processing core on a single shared-memory 12-core (SMP) machine. I don't have access to install htop, else I would simply use that. I don't need fancy graphs or meters, though they would be nice. For example, simply displaying: X X X X X X X X X X X X where each X is the percentage utilization of 1 of the 12 processing cores on my machine. FYI: I know I can simply look at the utilization in "top" and divide that number by the number of cores on my machine, but I prefer a solution that shows each core separately.

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  • Problem in understanding connectSlotsByName() in pyqt???

    - by Jebagnanadas
    Hi all, I couldn't understand the connectSlotsByName() method which is predominently used by pyuic4.. As far the class is single in a PyQt file it's ok since we can use self which will be associated with a single object throughout.. But when we try to use various classes from different files the problem and the need to use connectSlotsByName() arises.. Here's what i encountered which is weird.. I created a stacked widget.. I placed my first widget on it.. It has a button called "Next ". On clicking next it hides the current widget and adds another widget which has the "click me" button.. The problem here is the click event for "click me" button in second is not captured.. It's a minimal example that i can give for my original problem.. Please help me.. This is file No.1..(which has the parent stacked widget and it's first page). On clicking next it adds the second page which has "clickme" button in file2.. from PyQt4 import QtCore, QtGui import file2 class Ui_StackedWidget(QtGui.QStackedWidget): def __init__(self,parent=None): QtGui.QStackedWidget.__init__(self,parent) self.setObjectName("self") self.resize(484, 370) self.setWindowTitle(QtGui.QApplication.translate("self", "stacked widget", None, QtGui.QApplication.UnicodeUTF8)) self.createWidget1() def createWidget1(self): self.page=QtGui.QWidget() self.page.setObjectName("widget1") self.pushButton=QtGui.QPushButton(self.page) self.pushButton.setGeometry(QtCore.QRect(150, 230, 91, 31)) self.pushButton.setText(QtGui.QApplication.translate("self", "Next >", None, QtGui.QApplication.UnicodeUTF8)) self.addWidget(self.page) QtCore.QMetaObject.connectSlotsByName(self.page) QtCore.QObject.connect(self.pushButton,QtCore.SIGNAL('clicked()'),self.showWidget2) def showWidget2(self): self.page.hide() obj=file2.widget2() obj.createWidget2(self) if __name__ == "__main__": import sys app = QtGui.QApplication(sys.argv) ui = Ui_StackedWidget() ui.show() sys.exit(app.exec_()) Here's file2 from PyQt4 import QtGui,QtCore class widget2(): def createWidget2(self,parent): self.page = QtGui.QWidget() self.page.setObjectName("page") self.parent=parent self.groupBox = QtGui.QGroupBox(self.page) self.groupBox.setGeometry(QtCore.QRect(30, 20, 421, 311)) self.groupBox.setObjectName("groupBox") self.groupBox.setTitle(QtGui.QApplication.translate("self", "TestGroupBox", None, QtGui.QApplication.UnicodeUTF8)) self.pushButton = QtGui.QPushButton(self.groupBox) self.pushButton.setGeometry(QtCore.QRect(150, 120, 92, 28)) self.pushButton.setObjectName("pushButton") self.pushButton.setText(QtGui.QApplication.translate("self", "Click Me", None, QtGui.QApplication.UnicodeUTF8)) self.parent.addWidget(self.page) self.parent.setCurrentWidget(self.page) QtCore.QMetaObject.connectSlotsByName(self.page) QtCore.QObject.connect(self.pushButton,QtCore.SIGNAL('clicked()'),self.printMessage) def printMessage(self): print("Hai") Though in both the widgets(i mean pages) QtCore.QMetaObject.connectSlotsByName(self.page) the clicked signal in second dialog isn't getting processed. Thanks in advance.. Might be a beginner question..

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