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• memory alignment issues with union

  - by confucius

  Hi all, Is there guarantee, that memory for this object will be properly aligned if we create this object of this type in stack? union my_union { int value; char bytes[4]; }; If we create char bytes[4] in stack and then try to cast it to integer there might be alignment problem. We can avoid that problem by creating it in heap, however, is there such guarantee for union objects? Logically there should be, but I would like to confirm. Thanks.

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• Problem with operator ==

  - by CPPDev

  I am facing some problem with use of operator == in the following c++ program. #include < iostream> using namespace std; class A { public: A(char *b) { a = b; } A(A &c) { a = c.a; } bool operator ==(A &other) { return strcmp(a, other.a); } private: char *a; }; int main() { A obj("test"); A obj1("test1"); if(obj1 == A("test1")) { cout<<"This is true"<<endl; } } What's wrong with if(obj1 == A("test1")) line ?? Any help is appreciated.

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• Win32 api call via C# fails!

  - by user434186

  Hi. I have a C++ function exported as api like this: #define WIN322_API __declspec(dllexport) WIN322_API char* Test(LPSTR str); WIN322_API char* Test(LPSTR str) { return "hello"; } the function is exported as API correctly by the .DEF file, cause i can see it in Dependency Walker tool. Now i have a C# tester program: [DllImport("c:\\win322.dll")] public static extern string Test([MarshalAs(UnmanagedType.LPStr)] String str); private void Form1_Load(object sender, EventArgs e) { string _str = "0221"; Test(_str); // runtime error here! } on calling the Test() method i get the error: "A call to PInvoke function 'MyClient!MyClient.Form1::Test' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature." i tried many other data types and marshalings, but got nothing! plz help me!

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• Another C datatypes question

  - by b-gen-jack-o-neill

  Hello. Well, I completely get the most basic datatypes of C, like short, int, long, float, to be exact, all numerical types.These types are needed to be known perform right operations with right numbers. For example to use FPU to add two float numbers. So the compiler must know what the type is. But, when it comes to characters I am little bit off. I know that basic C datatype char is there for ASCII characters coding. But what I don´t know is, why you even need another datatype for characters. Why could not you just use 1 byte integer value to store ASCII character. If you call printf, you apecify the datatype in the call, so you could say to printf that the integer represents ASCII character. I dont know how cout resolves datatype, but I guess you could just specify it somehow. Another thing is, when you want to use Unicode, you must use datatype wchar. But, what if I would like to use some another, for example ISO, or Windows coding instead of UTF? Becouse wchar codes characters as UTF-16 or UTF-32 (I read its compiler specific). And, what if I would want to use for example some imaginary new 8 byte text coding? What datatype should I use for it? I am actually pretty confused of this, becouse I always expected that if I want to use UTF-32 instead of ASCII, I just tell compiler "get UTF-32 value of the character I typed and save it into 4 char field." I thought that text coding is to be dealt with by the end, print function for example. That I just need to specify the coding for the compiler to use, since Windows doesent use ASCII in win32 apps, I guess C compiler must convert the char I typed to ASCII from whatever the type is that windows sends to the C editor. And the last thing is, what if I want to use for example 25 Byte integer for some high math operations? C has no specify-yourself datatype. Yes, I know that this would be difficult since all the math operations would need to be changed, becouse CPU can not add 25 Bytes numbers together. But is there a way to do it? Or is there some math library for it? What if I want to compute Pi to 1000000000000000 digits? :) I know my question is pretty long, but I just wanted to explain my thoughts the best I can in English, since its not my native language it is difficult. And I believe there is simple answer to my question(s), something I missed that explains everything. I read lot about text coding, C tutorials, but nothing about his. Thank you for your time.

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• C#. Whats the fastest way to make an integer positive

  - by maxima120

  I asked wrong question previously and was swamped with negative votes... Let me try again... What is absolutely fastest way to make an int positive (given 50/50 distribution of pos/neg over time). To be nominated for an answer I will require MSIL analysis and not a guess or measuring of time with granny's watch... P.S. as one of variations I proposed i * i not because I wanted to do Sqrt(i * i) afterwards but because i will be used only once to be compared to a const. And if i * i will win competition I simply multiply the const.. Hence the following solution is valid: int trigger = realTrigger * realTrigger; i = SomeCalcs(); i = i * i; if(i < trigger) DoSomething(); P.P.S. pointless rant is not acceptable.. like: why do you need this, its BS! C# cannot tolerate developers like you!

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• CString error, 'CString': is not a member of 'ATL::CStringT<BaseType, StringTraits>'

  - by flavour404

  Hi, I am trying to do this: #include <atlstr.h> CHAR Filename; // [sp+26Ch] [bp-110h]@1 char v31; // [sp+36Ch] [bp-10h]@1 int v32; // [sp+378h] [bp-4h]@1 GetModuleFileNameA(0, &Filename, 0x100u); CString::CString(&v31, &Filename); But I am getting the compiler error C2039:'CString': is not a member of 'ATL::CStringT' This is a non MFC based dll, but according to the docs you should be able to use CString functionality with the include #include atlstr.h how do I make it work? Thanks

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• C++ input chaining in C#

  - by Monty

  I am trying to learn C# coming from C++. I am writing just some basic console stuff to get a feel for it and was wondering if it is possible to do simple chaining of inputs in C#. For example in C++: cout<<"Enter two numbers: "; cin >> int1 >> int2; You could then just input 3 5 and hit enter and the values will be fine. In C# however I have to split it up(as far as I can tell) like this: Console.Write("Enter the first number: "; int1 = (char)Console.Read(); Console.Writeline(""); Console.Write("Enter the second number: "; int2 = (char)Console.Read(); Maybe I am just missing something.

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• Retrieve names of running processes

  - by Dave DeLong

  Hi everyone, First off, I know that similar questions have been asked, but the answers provided haven't been very helpful so far (they all recommend one of the following options). I have a user application that needs to determine if a particular process is running. Here's what I know about the process: The name The user (root) It should already be running, since it's a LaunchDaemon, which means Its parent process should be launchd (pid 1) I've tried several ways to get this, but none have worked so far. Here's what I've tried: Running ps and parsing the output. This works, but it's slow (fork/exec is expensive), and I'd like this to be as fast as possible. Using the GetBSDProcessList function listed here. This also works, but the way in which they say to retrieve the process name (accessing kp_proc.p_comm from each kinfo_proc structure) is flawed. The resulting char* only contains the first 16 characters of the process name, which can be seen in the definition of the kp_proc structure: #define MAXCOMLEN 16 //defined in param.h struct extern_proc { //defined in proc.h ...snip... char p_comm[MAXCOMLEN+1]; ...snip... }; Using libProc.h to retrieve process information: pid_t pids[1024]; int numberOfProcesses = proc_listpids(PROC_ALL_PIDS, 0, NULL, 0); proc_listpids(PROC_ALL_PIDS, 0, pids, sizeof(pids)); for (int i = 0; i < numberOfProcesses; ++i) { if (pids[i] == 0) { continue; } char name[1024]; proc_name(pids[i], name, sizeof(name)); printf("Found process: %s\n", name); } This works, except it has the same flaw as GetBSDProcessList. Only the first portion of the process name is returned. Using the ProcessManager function in Carbon: ProcessSerialNumber psn; psn.lowLongOfPSN = kNoProcess; psn.highLongOfPSN = 0; while (GetNextProcess(&psn) == noErr) { CFStringRef procName = NULL; if (CopyProcessName(&psn, &procName) == noErr) { NSLog(@"Found process: %@", (NSString *)procName); } CFRelease(procName); } This does not work. It only returns process that are registered with the WindowServer (or something like that). In other words, it only returns apps with UIs, and only for the current user. I can't use -[NSWorkspace launchedApplications], since this must be 10.5-compatible. In addition, this only returns information about applications that appear in the Dock for the current user. I know that it's possible to retrieve the name of running processes (since ps can do it), but the question is "Can I do it without forking and exec'ing ps?". Any suggestions?

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• need identical string comparison function in php and java

  - by steelbytes

  I have sorted list of strings that I move between php and java. to be able to bsearch on this data, I need the same comparison function. any idea what string compare functions I can use that will always give the same result in both? eg php's strcmp() vs java's String.compareTo() yes I know I could make my own string compare that does char by char carefully, but I was hoping there's a simple answer. PS, don't care if case sensitive or not, as long as it is consistant.

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• ruby c extensions: character values over 127

  - by Adrian

  I am trying to make a C extension for Ruby that includes a method returning a string, which will sometimes have character values that need to be in an unsigned char. In http://github.com/shyouhei/ruby/blob/trunk/README.EXT, all of the functions listed for turning C strings into Ruby strings take signed chars. So I couldn't do this: unsigned char bytes[] = {0xf0, 0xf1, 0xf2}; return rb_str_new(bytes, 3); How could I make a method that returns these types of strings? In other words, how would I make a C extension with a method returning "\xff"?

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• using C function in C#

  - by andrew

  i have a dll, built with mingw one of the header files contains this: extern "C" { int get_mac_address(char * mac); //the function returns a mac address in the char * mac } I use this dll in another c++ app, built using Visual C++ (2008SP1), not managed, but plain c++ (simply include the header, and call the function) But now I have to use it in a C# application The problem is that i can't figure out how exactly (i'm new in .net programming) this is what i've tried public class Hwdinfo { [DllImport("mydll.dll")] public static extern void get_mac_address(string s); } When i call the function, nothing happens (the mydll.dll file is located in the bin folder of the c# app, and it gives me no errors or warnings whatsoever)

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• convert int to string for use in allegro function

  - by ace

  I am trying to run the following code using allegro. textout_ex(screen, font, numbComments , 100, 100, GREEN, BLACK); numbComments is an integer, the function prototype of this function is void textout_ex(BITMAP *bmp, const FONT *f, const char *s, int x, int y, int color, int bg); and i cannot, according to my understanding pass this integer in the third position. I therefore need to convert the integer into a string. I did it like this, but it didnt work. Help please? int score = numbComments; string Str; stringstream out; // YOU MUST INCLUDE <sstream> FOR THIS. out << score; Str = out.str(); and then tried to use the string Str, which didnt work

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• C: Cannot declare pointer inside if statement

  - by echedey lorenzo

  Hi, I have a pointer which points to a function. I would like to: if (mode == 0) { const unsigned char *packet = read_serial_packet(src, &len); } else { const unsigned char *packet = read_network_packet(fd, &len); } But I cannot do it because my compiler complains when I first use the pointer later in the code. error: 'packet' undeclared (first use in this function) This is strange. It worked without the if statement, but now I need my program to be able to get data from different sources. Isn't it possible to do this? I think so. If it isn't, is there any other simple way to get what I am trying? Thanks a lot.

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• QGraphicsItem repaint

  - by onurozcelik

  I want to change text color inside a rectangle periyodically Here is my trial: TrainIdBox::TrainIdBox() { boxRect = QRectF(0,0,40,15); testPen = QPen(Qt:red); i=0; startTimer(500); } QRectF TrainIdBox::boundingRect() const { return boxRect; } void TrainIdBox::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) { Q_UNUSED(widget); Q_UNUSED(option); painter->setPen(QPen(drawingColor,2)); painter->drawRect(boxRect); painter->setPen(testPen); painter->drawText(boxRect,Qt::AlignCenter,"TEST"); } void TrainIdBox::timerEvent(QTimerEvent *te) { testPen = i % 2 == 0 ? QPen(Qt::green) : QPen(Qt::yellow); i++; update(boxRect); } This code does not working properly. What is wrong?

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• make error in re-building ns2

  - by user3702405

  I have implemented a new routing protocol named AODV2 in ns-2.35. I am using ns-2.35 in fedora 13. All .cc files have a .o file with them that means recompilation is done. But I am getting an error in response to the 'make' command. Error is shown below: trace/cmu-trace.o: In function hdr_aodv2::access(Packet const*)': cmu-trace.cc:(.text._ZN9hdr_aodv26accessEPK6Packet[hdr_aodv2::access(Packet const*)]+0x7): undefined reference tohdr_aodv2::offset_2' collect2: ld returned 1 exit status make: * [ns] Error 1 I don't know how to remove this error, Can anyone help me please? Thanks, Naeem

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• How does sizeof calculate the size of structures

  - by Gearoid Murphy

  I know that a char and an int are calculated as being 8 bytes on 32 bit architectures due to alignment, but I recently came across a situation where a structure with 3 shorts was reported as being 6 bytes by the sizeof operator. Code is as follows: #include <iostream> using namespace std ; struct IntAndChar { int a ; unsigned char b ; }; struct ThreeShorts { unsigned short a ; unsigned short b ; unsigned short c ; }; int main() { cout<<sizeof(IntAndChar)<<endl; // outputs '8' cout<<sizeof(ThreeShorts)<<endl; // outputs '6', I expected this to be '8' return 0 ; } Compiler : g++ (Debian 4.3.2-1.1) 4.3.2. This really puzzles me, why isn't alignment enforced for the structure containing 3 shorts?

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• How best to implement publicly accessible constants in C#

  - by DanM

  There seem to be three choices for implementing publicly accessible constants in C#. I'm curious if there are any good reason to choose one over the other or if it's just a matter of personal preference. Choice 1 - private field plus property getter private const string _someConstant = "string that will never change"; public string SomeConstant { get { return _someConstant; } } Choice 2 - property getter only public string SomeConstant { get { return "string that will never change"; } } Choice 3 - public field only public const string SomeConstant = "string that will never change"; Which do you recommend and why?

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• How come this image won't resize to fit the sprite?

  - by George Edison

  I have this snippet of ActionScript code that is supposed to resize an image to fit the sprite: package { import flash.display.Sprite; import flash.display.Bitmap; import flash.events.Event; public class Main extends Sprite { [Embed(source = 'img.png')] private var TheImage:Class; public static const TheImageWidth:Number = 1300; public static const TheImageHeight:Number = 1300; public function Main():void { if (stage) init(); else addEventListener(Event.ADDED_TO_STAGE, init); } private function init(e:Event = null):void { removeEventListener(Event.ADDED_TO_STAGE, init); // entry point var image:Bitmap = new TheImage(); addChild(image); image.scaleX = width / TheImageWidth; image.scaleY = height / TheImageHeight; } } } Why isn't it working?

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• J2ME/Java: Referencing StringBuffer through Threads

  - by Jemuel Dalino

  This question might be long, but I want to provide much information. Overview: I'm creating a Stock Quotes Ticker app for Blackberry. But I'm having problems with my StringBuffer that contains an individual Stock information. Process: My app connects to our server via SocketConnection. The server sends out a formatted set of strings that contains the latest Stock trade. So whenever a new trade happens, the server will send out an individual Stock Quote of that trade. Through an InputStream I am able to read that information and place each character in a StringBuffer that is referenced by Threads. By parsing based on char3 I am able to determine a set of stock quote/information. char1 - to separate data char3 - means end of a stock quote/information sample stock quote format sent out by our server: stock_quote_name(char 1)some_data(char1)some_data(char1)(char3) My app then parses that stock quote to compare certain data and formats it how it will look like when displayed in the screen. When trades happen gradually(slow) the app works perfectly. However.. Problem: When trades happen too quickly and almost at the same time, My app is not able to handle the information sent efficiently. The StringBuffer has its contents combined with the next trade. Meaning Two stock information in one StringBuffer. field should be: Stock_quote_name some_data some_data sample of what's happening: Stock_quote_name some_data some_dataStock_quote_name some_data some_data here's my code for this part: while (-1 != (data = is.read())) { sb.append((char)data); while(3 != (data = is.read())) { sb.append((char)data); } UiApplication.getUiApplication().invokeLater(new Runnable() { public void run() { try { synchronized(UiApplication.getEventLock()) { SetStringBuffer(sb); DisplayStringBuffer(); RefreshStringBuffer(); } } catch (Exception e) { System.out.println("Error in setting stringbuffer: " + e.toString()); } } }); } public synchronized void DisplayStringBuffer() { try { //parse sb - string buffer ...... } catch(Exception ex) { System.out.println("error in DisplayStringBuffer(): " + ex.toString()); } } public synchronized void SetStringBuffer(StringBuffer dataBuffer) { this.sb =dataBuffer; System.out.println(sb); } public synchronized void RefreshStringBuffer() { this.sb.delete(0, this.sb.length()); } From what I can see, when trades happen very fast, The StringBuffer is not refreshed immediately and still has the contents of the previous trade, when i try to put new data. My Question is: Do you guys have any suggestion on how i can put data into the StringBuffer, without the next information being appended to the first content

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• QT clicked signal dosnt work on QStandardItemModel with tree view

  - by user63898

  Hello i have this code in QT and all i want to to catch the clicked event when some one clicking in one of the treeview rows without success here is my code: (parant is the qMmainwindow) m_model = new QStandardItemModel(0, 5, parent); // then later in the code i have proxyModel = new QSortFilterProxyModel; proxyModel->setDynamicSortFilter(true); setSourceModel(createMailModel(parent)); ui.treeView->setModel(proxyModel); ui.treeView->setSortingEnabled(true); ui.treeView->sortByColumn(4, Qt::DescendingOrder); // and my signal/slot looks like this but its not working //and im not getting eny clicked event fired connect(ui.treeView,SIGNAL(Clicked(const QModelIndex& ) ), this,SLOT( treeViewSelectedRow(const QModelIndex& ) ) ); also how can i debug QT signal/slots so i can see some debug massages printing when something is wrong ?

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• QValidator for hex input

  - by Evan Teran

  I have a Qt widget which should only accept a hex string as input. It is very simple to restrict the input characters to [0-9A-Fa-f], but I would like to have it display with a delimiter between "bytes" so for example if the delimiter is a space, and the user types 0011223344 I would like the line edit to display 00 11 22 33 44 Now if the user presses the backspace key 3 times, then I want it to display 00 11 22 3. I almost have what i want, so far there is only one subtle bug involving using the delete key to remove a delimiter. Does anyone have a better way to implement this validator? Here's my code so far: class HexStringValidator : public QValidator { public: HexStringValidator(QObject * parent) : QValidator(parent) {} public: virtual void fixup(QString &input) const { QString temp; int index = 0; // every 2 digits insert a space if they didn't explicitly type one Q_FOREACH(QChar ch, input) { if(std::isxdigit(ch.toAscii())) { if(index != 0 && (index & 1) == 0) { temp += ' '; } temp += ch.toUpper(); ++index; } } input = temp; } virtual State validate(QString &input, int &pos) const { if(!input.isEmpty()) { // TODO: can we detect if the char which was JUST deleted // (if any was deleted) was a space? and special case this? // as to not have the bug in this case? const int char_pos = pos - input.left(pos).count(' '); int chars = 0; fixup(input); pos = 0; while(chars != char_pos) { if(input[pos] != ' ') { ++chars; } ++pos; } // favor the right side of a space if(input[pos] == ' ') { ++pos; } } return QValidator::Acceptable; } }; For now this code is functional enough, but I'd love to have it work 100% as expected. Obviously the ideal would be the just separate the display of the hex string from the actual characters stored in the QLineEdit's internal buffer but I have no idea where to start with that and I imagine is a non-trivial undertaking. In essence, I would like to have a Validator which conforms to this regex: "[0-9A-Fa-f]( [0-9A-Fa-f])*" but I don't want the user to ever have to type a space as delimiter. Likewise, when editing what they types, the spaces should be managed implicitly.

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• C++ Linux getpeername IP family

  - by gln

  hi In my Linux C++ application I'm using getpeername in order to get the peer IP. my problem is: when I enable the IPv6 on my machine the IP I got from the peer is with family IF_INET6 although it is IPv4. code: int GetSockPeerIP( int sock) { struct sockaddr_storage ss; struct socklen_t salen = sizeof(ss); struct sockaddr *sa; memset(&ss,0,salen); sa = (sockaddr *)&ss; if(getpeername(sock,sa,&salen) != 0) { return -1; } char * ip=NULL: if(sa->sa_family == AF_INET) { ip = inet_ntoa((struct sockaddr_in *)sa)->sin_addr); } else { //ip = how to convert IPv6 to char IP? } return 0; } how can I fix it? thanks1

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• PowerShell 2.0 and how to handle exceptions ?

  - by Primoz

  Why I get error message printed on the console when running these two simple samples ? I want that I get "Error testing :)" printed on the console insted of: Get-WmiObject : The RPC server is unavailable. (Exception from HRESULT: 0x800706BA) At line:3 char:15 + Get-WmiObject <<<< -ComputerName possibly.nonexisting.domain.com -Credential (Get-Credential) -Class Win32_logicaldisk + CategoryInfo : InvalidOperation: (:) [Get-WmiObject], COMException + FullyQualifiedErrorId : GetWMICOMException,Microsoft.PowerShell.Commands.GetWmiObjectCommand or Attempted to divide by zero. At line:3 char:13 + $i = 1/ <<<< 0 + CategoryInfo : NotSpecified: (:) [], ParentContainsErrorRecordException + FullyQualifiedErrorId : RuntimeException First example: try { $i = 1/0 Write-Host $i } catch [Exception] { Write-Host "Error testing :)" } Second example: try { Get-WmiObject -ComputerName possibly.nonexisting.domain.com -Credential (Get-Credential) -Class Win32_logicaldisk } catch [Exception] { Write-Host "Error testing :)" } Thank you very much!

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• stl::map insert segmentation fault

  - by Jakub Czaplicki

  Why does this code stop with the segmentation fault : class MapFile { public: /* ... */ std::map <unsigned int, unsigned int> inToOut; }; bool SwitchMapFile::LoadMapFile( const wxString& fileName ) { /* ... */ inToOut.insert( std::make_pair(spmPort,fibreId) ); } but this one works fine : class MapFile { public: /* ... */ }; bool MapFile::LoadMapFile( const wxString& fileName ) { /* ... */ std::map <unsigned int, unsigned int> inToOut; inToOut.insert( std::make_pair(input,output) ); } ?

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• Glib segfault g_free hash table

  - by Mike

  I'm not quite sure why if I try to free the data I get segfault. Any help will be appreciate it. static GHashTable *hashtable; static void add_inv(char *q) { gpointer old_key, old_value; if(!g_hash_table_lookup_extended(hashtable, q, &old_key, &old_value)){ g_hash_table_insert(hashtable, g_strdup(q), GINT_TO_POINTER(10)); }else{ (old_value)++; g_hash_table_insert(hashtable, g_strdup(q), old_value); g_hash_table_remove (hashtable, q); // segfault g_free(old_key); // segfault g_free(old_value); // segfault } } ... int main(int argc, char *argv[]){ hashtable = g_hash_table_new(g_str_hash, g_str_equal); ... g_hash_table_destroy(hashtable); }

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