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  • Implications of trying to double free memory space in C

    - by SidNoob
    Here' my piece of code: #include <stdio.h> #include<stdlib.h> struct student{ char *name; }; int main() { struct student s; s.name = malloc(sizeof(char *)); // I hope this is the right way... printf("Name: "); scanf("%[^\n]", s.name); printf("You Entered: \n\n"); printf("%s\n", s.name); free(s.name); // This will cause my code to break } All I know is that dynamic allocation on the 'heap' needs to be freed. My question is, when I run the program, sometimes the code runs successfully. i.e. ./struct Name: Thisis Myname You Entered: Thisis Myname I tried reading this I've concluded that I'm trying to double-free a piece of memory i.e. I'm trying to free a piece of memory that is already free? (hope I'm correct here. If Yes, what could be the Security Implications of a double-free?) While it fails sometimes as its supposed to: ./struct Name: CrazyFishMotorhead Rider You Entered: CrazyFishMotorhead Rider *** glibc detected *** ./struct: free(): invalid next size (fast): 0x08adb008 *** ======= Backtrace: ========= /lib/tls/i686/cmov/libc.so.6(+0x6b161)[0xb7612161] /lib/tls/i686/cmov/libc.so.6(+0x6c9b8)[0xb76139b8] /lib/tls/i686/cmov/libc.so.6(cfree+0x6d)[0xb7616a9d] ./struct[0x8048533] /lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xe6)[0xb75bdbd6] ./struct[0x8048441] ======= Memory map: ======== 08048000-08049000 r-xp 00000000 08:01 288098 /root/struct 08049000-0804a000 r--p 00000000 08:01 288098 /root/struct 0804a000-0804b000 rw-p 00001000 08:01 288098 /root/struct 08adb000-08afc000 rw-p 00000000 00:00 0 [heap] b7400000-b7421000 rw-p 00000000 00:00 0 b7421000-b7500000 ---p 00000000 00:00 0 b7575000-b7592000 r-xp 00000000 08:01 788956 /lib/libgcc_s.so.1 b7592000-b7593000 r--p 0001c000 08:01 788956 /lib/libgcc_s.so.1 b7593000-b7594000 rw-p 0001d000 08:01 788956 /lib/libgcc_s.so.1 b75a6000-b75a7000 rw-p 00000000 00:00 0 b75a7000-b76fa000 r-xp 00000000 08:01 920678 /lib/tls/i686/cmov/libc-2.11.1.so b76fa000-b76fc000 r--p 00153000 08:01 920678 /lib/tls/i686/cmov/libc-2.11.1.so b76fc000-b76fd000 rw-p 00155000 08:01 920678 /lib/tls/i686/cmov/libc-2.11.1.so b76fd000-b7700000 rw-p 00000000 00:00 0 b7710000-b7714000 rw-p 00000000 00:00 0 b7714000-b7715000 r-xp 00000000 00:00 0 [vdso] b7715000-b7730000 r-xp 00000000 08:01 788898 /lib/ld-2.11.1.so b7730000-b7731000 r--p 0001a000 08:01 788898 /lib/ld-2.11.1.so b7731000-b7732000 rw-p 0001b000 08:01 788898 /lib/ld-2.11.1.so bffd5000-bfff6000 rw-p 00000000 00:00 0 [stack] Aborted So why is it that my code does work sometimes? i.e. the compiler is not able to detect at times that I'm trying to free an already freed memory. Has it got to do something with my stack/heap size?

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  • JNA array structure

    - by Burny
    I want to use a dll (IEC driver) in Java, for that I am using JNA. The problem in pseudo code: start the server allocate new memory for an array (JNA) client connect writing values from an array to the memory sending this array to the client client disconnect new client connect allocate new memory for an array (JNA) - JVM crash (EXCEPTION_ACCESS_VIOLATION) The JVM crash not by primitve data types and if the values will not writing from the array to the memory. the code in c: struct DataAttributeData CrvPtsArrayDAData = {0}; CrvPtsArrayDAData.ucType = DATATYPE_ARRAY; CrvPtsArrayDAData.pvData = XYValDAData; XYValDAData[0].ucType = FLOAT; XYValDAData[0].uiBitLength = sizeof(Float32)*8; XYValDAData[0].pvData = &(inUpdateValue.xVal); XYValDAData[1].ucType = FLOAT; XYValDAData[1].uiBitLength = sizeof(Float32)*8; XYValDAData[1].pvData = &(inUpdateValue.yVal); Send(&CrvPtsArrayDAData, 1); the code in Java: DataAttributeData[] data_array = (DataAttributeData[]) new DataAttributeData() .toArray(d.bitLength); for (DataAttributeData d_temp : data_array) { d_temp.data = new Memory(size / 8); d_temp.type = type_iec; d_temp.bitLength = size; d_temp.write(); } d.data = data_array[0].getPointer(); And then writing values whith this code: for (int i = 0; i < arraySize; i++) { DataAttributeData dataAttr = new DataAttributeData(d.data.share(i * d.size())); dataAttr.read(); dataAttr.data.setFloat(0, f[i]); dataAttr.write(); } the struct in c: struct DataAttributeData{ unsigned char ucType; int iArrayIndex; unsigned int uiBitLength; void * pvData;}; the struct in java: public static class DataAttributeData extends Structure { public DataAttributeData(Pointer p) { // TODO Auto-generated constructor stub super(p); } public DataAttributeData() { // TODO Auto-generated constructor stub super(); } public byte type; public int iArrayIndex; public int bitLength; public Pointer data; @Override protected List<String> getFieldOrder() { // TODO Auto-generated method stub return Arrays.asList(new String[] { "type", "iArrayIndex", "bitLength", "data" }); } } Can anybody help me?

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  • Facebook,Android- How to get friends birthday from facebook

    - by Eriz
    I tried to goto lots of questions on this forum but could not find one useful so i decided to ask one myself. I want to pull the birthday's of all the friends in the users friend list. After going through a lot of stuff i found there are 2 ways to do that 1. Graph API 2. FQL Query So, my first question is , which one of them is better/easy to integrate in the app. Q2. http://developers.facebook.com/docs/tutorials/androidsdk/3.0/scrumptious/ is this tutorial useful for what i want to do. Q3. If i use Graph API/FQL Query , could you please give me a link which is helpful or a Code snippet Thanks In Advance, Eriz

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  • How are iterators and pointers related?

    - by sharptooth
    Code with iterators looks pretty much like code with pointers. Iterators are of some obscure type (like std::vector<int>::iterator for example). What I don't get is how iterators and pointer are related to each other - is an iterator a wrapper around a pointer with overloaded operations to advance to adjacent elements or is it something else?

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  • VB.NET SqlException Was Unhandled

    - by Daniel
    I am trying some SQL code but I get an error when I try this code. Main.database.ExecuteCommand("UPDATE Contacts SET first_name='" + c.first_name + _ "', middle='" + c.middle + _ "', last_name='" + c.last_name + _ "', age='" + c.age + _ "', mobile_phone='" + c.mobile_phone + _ "', home_phone='" + c.home_phone + _ "', work_phone='" + c.work_phone + _ "', home_street='" + c.home_street + _ "', home_city='" + c.home_city + _ "', home_state='" + c.home_state + _ "', home_zip='" + c.home_zip + _ "', work_street='" + c.work_street + _ "', work_city='" + c.work_city + _ "', work_state='" + c.work_state + _ "', work_zip='" + c.work_zip + _ "', home_www='" + c.home_www + _ "', work_www='" + c.work_www + _ "', home_email='" + c.home_email + _ "', work_email='" + c.work_email + _ "' WHERE first_name='" + c.first_name + _ "' AND last_name='" + c.last_name + "'") I get the following error Sql Exception was unhandled The data types text and varchar are incompatible in the equal to operator.

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  • In html <a href> tag, how to call servlet before opening file dialog for download (save as)?

    - by deepthinker121
    Hi All, I am developing a web-app where I want to provide a download link to users - so they can download a zip file from my server. Now, my requirement is that I want to execute some processing logic contained in a servlet before displaying the file dialog to the user for 'zip' files. So If I write <a href="abc.zip".......> then it opens a file dialog asking the user to select the location where this file can be saved But if I want a servlet's doGet method to do some preprocessing - say like building the zip file , then how can I first call the servlet and then open the file dialog. Will the following snippet work? <a href="MyHandlerServlet;abc.zip".......> Thanks for your help !!

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  • Including Build Date strings in a C# project

    - by David Rutten
    I'd like to hard code the build date into my application (DD-mmmm-YYYY), but how do I embed this constant into the code? I thought perhaps I could make a pre-build event that executes a *.bat file that updates a textfile which is resourced, but it sounds pretty involved. What's the best approach?

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  • Tab-Bar not hiding on all views

    - by Sheehan Alam
    I have a tab-bar controller that loads a RootView. The RootView has 4 buttons that will load a UITableView I don't want my tab-bar to be visible in the RootView so I added the following code: -(void)viewDidLoad{ self.hidesBottomBarWhenPushed = YES; } When I initially load the app the tab-bar doesn't appear, but when I click on a button, and go back to the RootView the tab-bar still appears. I have tried placing this code in viewWillAppear and other application lifecycle methods but no luck.

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  • how to properly transfer user input from index to invoice?

    - by Romel
    I got a dillema, I'm trying to find a solution for my code. How do I make it so that when the user inputs a given quantity in the text box from the index.php it will transfer that input quantity to the invoice.php. I've tried doing the post method but it seems like it's not working :/ As always, any help or suggestions will be greatly appreciated! I hope it's something simple:( Here's my code: index.php <html> <style> body{ background-image: url('URL HERE'); font-family: "Helvetica"; font-size:15px; } h1{ color:black; text-align:center; } p{ font-size:15px; } </style> <h1> STORE TITLE HERE </h1> <body> <form action="login.php" method="post"> <?php //Include products info.inc (Which holds all our product arrays and info) //Credit: Tracy & Mark (THank you!) include 'products_info.inc'; /*The following code centers my table on the page, makes the table background white, makes the table 50% of the browser window, gives it a border of 1 px, gives a padding of 2 px between the cell border and content, and gives 1 px of spacing between cells. */ echo "<table align=center bgcolor='FFFFFF' width=50% border=1 cellpadding=1 cellspacing=2>"; //Credit: Tracy & Mark (THank you!) echo '<th>Product</th> <th>Description</th> <th>Price</th> <th>Quantity</th>'; //The following code loops through the whole table body and then prints each row. for($i=0; $i<count($allfood); $i++) { //Credit: Tracy & Mark (THank you!) echo "<tr align=center>"; echo "<td>{$allfood[$i]['Product']}</td>"; echo "<td>{$allfood[$i]['Description']}</td>"; echo "<td>{$allfood[$i]['Price']}</td>"; echo "<td>{$allfood[$i]['Quantity']}</td>"; echo "</tr>"; } //This code ends the table. echo "</table>"; echo "<br>"; ?> <br><center><input type='submit' name='purchase' value='Purchase'></center> </form> </body> </html> And here's my invoice.php <html> <style> body{ background-image: url('URL HERE'); font-family: "Helvetica"; font-size:15px; } h1{ color:black; text-align:center; } p{ font-size:15px; } </style> <h1> Invoice </h1> </html> <?php //Include products info.inc (Which holds all our product arrays and info) //Credit: Tracy & Mark (Thank you!) include 'products_info.inc'; //Display the invoice & 'WELCOME USER. THANK YOU FOR USING THIS DAMN THING msg' /*The following code centers my invoice table on the page, makes the table background white, makes the table 50% of the browser window, gives it a border of 1 px, gives a padding of 2 px between the cell border and content, and gives 1 px of spacing between cells. */ echo "<table align=center bgcolor='FFFFFF' width=50% border=1 cellpadding=1cellspacing=2>"; echo "<tr>"; echo "<td align=center><b>Product</b></td>"; echo "<td align=center><b>Quantity</b></td>"; echo "<td align=center><b>Price</></td>"; echo "<td align=center><b>Extended Price</b></td>"; echo "</tr>"; for($i=0; $i<count($allfood); $i++) { //Credit: Tracy & Mark (Thank you!) $qty= @$_POST['Quantity']['$i']; // This calculates the price if the user orders more than 1 item. $extendedprice = $qty*$allfood[$i]['Price']; echo "<tr>"; echo "<td align=center>{$allfood[$i]['Product']}</td>"; echo "<td align=center>$extendedprice</td>"; echo "<td align=center>{$allfood[$i]['Price']}</td>"; echo "</tr>"; } // The goal here was to make it so that if the user selected a certain quantity from index.php, it would carry over and display on the invoice.php if ($qty = 0) { echo "please choose 1"; } elseif ($qty > 0) { echo $qty; } /*echo "<tr>"; echo "<td align=center>Subtotal</b></td>"; echo "<td align=center></td>"; echo "<td align=center></td>"; echo "<tr>"; echo "<td align=center>Tax at 5.75%</td>"; echo "<td align=center></td>"; echo "<td align=center></td>"; echo "<tr>"; echo "<td align=center><b>Grand total</b></td>"; echo "<td align=center></td>"; echo "<td align=center></td>"; */ echo "</table>"; ?> <br> <center> <form action="index.php" method="post"> <input type="submit" name="home" value="Back to homepage"> </form> </center>

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  • Variable inside of the markup for an asp:HyperLink NavigationUrl property?

    - by RichAmberale
    Hi, I'm new to ASP.NET and can't figure out how to accomplish this... My code (that needs fixing): <asp:HyperLink runat="server" NavigateUrl="~/EditReport.aspx?featureId=<%= featureId %>" ImageUrl="~/new.gif" /> featureId gets defined as an integer in the backing code. I want href's like... /EditReport.aspx?featureId=2224 ...but instead I am getting... /EditReport.aspx?featureId=<%= featureId %>

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  • C# Compiler Directives

    - by pm_2
    I’m looking at some C# code, and have come across the following statement: #if DEBUG // Do something here #else // Do something else #endif I assumed that DEBUG would be a defined somewhere as follows: #define DEBUG But I’m unable to find such a definition, although the code seems to behave as though it were set. Is DEBUG a special case, and if so, how is it set / unset?

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  • How do I put all types implementing a certain generic interface in a dictionary?

    - by James Wenday
    Given a particular interface ITarget<T> and a particular type myType, here's how you would determine T if myType implements ITarget<T>. (This code snippet is taken from the answer to an earlier question.) foreach (var i in myType.GetInterfaces ()) if (i.IsGenericType && i.GetGenericTypeDefinition() == typeof(ITarget<>)) return i.GetGenericArguments ()[0] ; However, this only checks a single type, myType. How would I create a dictionary of all such type parameters, where the key is T and the value is myType? I think it would look something like this: var searchTarget = typeof(ITarget<>); var dict = Assembly.GetExecutingAssembly().[???] .Where(t => t.IsGenericType && t.GetGenericTypeDefinition() == searchTarget) .[???]; What goes in the blanks?

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  • C++ -- How can we call "delete this; " in a const-member function?

    - by q0987
    Hello all, I saw the code snippet as follows: class UPNumber { public: UPNumber(); UPNumber(int initValue); ... // pseudo-destructor (a const member function, because // even const objects may be destroyed) void destroy() const { delete this; } // why this line is correct??? ... private: ~UPNumber(); }; First, I am sure that above class definition is correct. Here is my question, why we can define the function 'destroy' as above? The reason being asking is that why we can modify 'this' in a const-member function? Thank you

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  • App.config settings, environment variable as partial path

    - by Jean-Bernard Pellerin
    I'm new to tinkering with app.config and xml, and am currently doing some refactoring in some code I haven't written. Currently we have a snippet which looks like this: <setting name="FirstSetting" serializeAs="String"> <value>Data Source=C:\Documents and Settings\All Users\ApplicationData\Company ...;Persist Security Info=False</value> What I'd like to do is have it instead point to something like ${PROGRAMDATA}\Company\... How can I achieve this, keeping in mind that PROGRAMDATA will not always point to C:\ProgramData ?

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  • Set value of textarea in jquery

    - by GONeale
    I am attempting to set a value in a textarea field using jquery with the following code: $("textarea#ExampleMessage").attr("value", result.exampleMessage); The issue is, once this code executes, it is not altering the text in the textarea? However when performing an alert($("textarea#ExampleMessage").attr("value")) the newly set value is returned?

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  • C++ conditional compilation

    - by Shaown
    I have the following code snippet #ifdef DO_LOG #define log(p) record(p) #else #define log(p) #endif void record(char *data){ ..... ..... } Now if I call log("hello world") in my code and DO_LOG isn't defined, will the line be compiled, in other words will it eat up the memory for the string "hello world"? P.S. There are a lot of record calls in the program and it is memory sensitive, so is there any other way to conditionally compile so that it only depends on the #define DO_LOG? Thanks in advance.

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  • How to manipulate file paths intelligently in .Net 3.0?

    - by Hamish Grubijan
    Scenario: I am maintaining a function which helps with an install - copies files from PathPart1/pending_install/PathPart2/fileName to PathPart1/PathPart2/fileName. It seems that String.Replace() and Path.Combine() do not play well together. The code is below. I added this section: // The behavior of Path.Combine is weird. See: // http://stackoverflow.com/questions/53102/why-does-path-combine-not-properly-concatenate-filenames-that-start-with-path-dir while (strDestFile.StartsWith(@"\")) { strDestFile = strDestFile.Substring(1); // Remove any leading backslashes } Debug.Assert(!Path.IsPathRooted(strDestFile), "This will make the Path.Combine(,) fail)."); in order to take care of a bug (code is sensitive to a constant @"pending_install\" vs @"pending_install" which I did not like and changed (long story, but there was a good opportunity for constant reuse). Now the whole function: //You want to uncompress only the files downloaded. Not every file in the dest directory. private void UncompressFiles() { string strSrcDir = _application.Client.TempDir; ArrayList arrFiles = new ArrayList(); GetAllCompressedFiles(ref arrFiles, strSrcDir); IEnumerator enumer = arrFiles.GetEnumerator(); while (enumer.MoveNext()) { string strDestFile = enumer.Current.ToString().Replace(_application.Client.TempDir, String.Empty); // The behavior of Path.Combine is weird. See: // http://stackoverflow.com/questions/53102/why-does-path-combine-not-properly-concatenate-filenames-that-start-with-path-dir while (strDestFile.StartsWith(@"\")) { strDestFile = strDestFile.Substring(1); // Remove any leading backslashes } Debug.Assert(!Path.IsPathRooted(strDestFile), "This will make the Path.Combine(,) fail)."); strDestFile = Path.Combine(_application.Client.BaseDir, strDestFile); strDestFile = strDestFile.Replace(Path.GetExtension(strDestFile), String.Empty); ZSharpLib.ZipExtractor.ExtractZip(enumer.Current.ToString(), strDestFile); FileUtility.DeleteFile(enumer.Current.ToString()); } } Please do not laugh at the use of ArrayList and the way it is being iterated - it was pioneered by a C++ coder during a .Net 1.1 era. I will change it. What I am interested in: what is a better way of replacing PathPart1/pending_install/PathPart2/fileName with PathPart1/PathPart2/fileName within the current code. Note that _application.Client.TempDir is just _application.Client.BaseDir + @"\pending_install". While there are many ways to improve the code, I am mainly concerned with the part which has to do with String.Replace(...) and Path.Combine(,). I do not want to make changes outside of this function. I wish Path.Combine(,) took an optional bool flag, but it does not. So ... given my constraints, how can I rework this so that it starts to sucks less? Thanks!

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  • how to set the name of the node using userobjects

    - by apoorva
    How to set the node text.Here is the code am using public TreeCreation(final ArrayList houseList){ Apartment= new DefaultMutableTreeNode("Apartment"); for(int i=0;i by passing the userObject the name of the object is being displayed on the node ,how do i change the code to display h.HouseName when am using userObjects node.getUserObject(hs.HouseName);

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  • Getting below error when trying to register a generic class with a implementation using .net 2.0

    - by Gaurav Saxena
    Code: StructureMapConfiguration.BuildInstancesOf().AsSingletons().TheDefaultIsConcreteType(); Error: StructureMap Exception Code: 190 Can not create a Generic PluginFamily for PluginFamily MIGExcel.Service.IPersistenceService1[[MIGExcel.Model.Contact, WizardModel, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]. Check that the basic type MIGExcel.Service.IPersistenceService1 is configured as a PluginFamily. These Generic types are configured within StructureMap as PluginFamily's: MIGExcel.Service.IPersistenceService`1[[MIGExcel.Model.Contact, WizardModel, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]],MIGExcel.Service;

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  • When is 'drawRect' called?

    - by Egil
    I have some custom drawing code in drawRect which also performs some calculation of sizes. When is the earliest I can be sure that this code has been loaded, e.g. if I want to modify it's containers size accordingly?

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