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• Memory allocation for collections in .NET

  - by Yogendra

  This might be a dupe. I did not find enough information on this. I was discussing memory allocation for collections in .Net. Where is the memory for elements allocated in a collection? List<int> myList = new List<int>(); The variable myList is allocated on stack and it references the List object created on heap. The question is when int elements are added to the myList, where would they be created ? Can anyone point the right direction?

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• C++ operator new, object versions, and the allocation sizes

  - by mizubasho

  Hi. I have a question about different versions of an object, their sizes, and allocation. The platform is Solaris 8 (and higher). Let's say we have programs A, B, and C that all link to a shared library D. Some class is defined in the library D, let's call it 'classD', and assume the size is 100 bytes. Now, we want to add a few members to classD for the next version of program A, without affecting existing binaries B or C. The new size will be, say, 120 bytes. We want program A to use the new definition of classD (120 bytes), while programs B and C continue to use the old definition of classD (100 bytes). A, B, and C all use the operator "new" to create instances of D. The question is, when does the operator "new" know the amount of memory to allocate? Compile time or run time? One thing I am afraid of is, programs B and C expect classD to be and alloate 100 bytes whereas the new shared library D requires 120 bytes for classD, and this inconsistency may cause memory corruption in programs B and C if I link them with the new library D. In other words, the area for extra 20 bytes that the new classD require may be allocated to some other variables by program B and C. Is this assumption correct? Thanks for your help.

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• Is memory allocation in linux non-blocking?

  - by Mark

  I am curious to know if the allocating memory using a default new operator is a non-blocking operation. e.g. struct Node { int a,b; }; ... Node foo = new Node(); If multiple threads tried to create a new Node and if one of them was suspended by the OS in the middle of allocation, would it block other threads from making progress? The reason why I ask is because I had a concurrent data structure that created new nodes. I then modified the algorithm to recycle the nodes. The throughput performance of the two algorithms was virtually identical on a 24 core machine. However, I then created an interference program that ran on all the system cores in order to create as much OS pre-emption as possible. The throughput performance of the algorithm that created new nodes decreased by a factor of 5 relative the the algorithm that recycled nodes. I'm curious to know why this would occur. Thanks. *Edit : pointing me to the code for the c++ memory allocator for linux would be helpful as well. I tried looking before posting this question, but had trouble finding it.

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• Memory allocation for a matrix in C

  - by Snogzvwtr

  Why is the following code resulting in Segmentation fault? (I'm trying to create two matrices of the same size, one with static and the other with dynamic allocation) #include <stdio.h> #include <stdlib.h> //Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; int a[X][Y]; int** b = (int**) malloc(sizeof(int*) * X); for(i=0; i<X; i++){ b[i] = malloc (sizeof(int) * Y); } } Weirdly enough, if I comment out one of the matrix definitions, the code runs fine. Like this: #include <stdio.h> #include <stdlib.h> //No Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; //int a[X][Y]; int** b = (int**) malloc(sizeof(int*) * X); for(i=0; i<X; i++){ b[i] = malloc (sizeof(int) * Y); } } or #include <stdio.h> #include <stdlib.h> //No Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; int a[X][Y]; //int** b = (int**) malloc(sizeof(int*) * X); //for(i=0; i<X; i++){ // b[i] = malloc (sizeof(int) * Y); //} } I'm running gcc on Linux on a 32-bit machine.

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• MIPS $gp register

  - by Hristo

  Is there a danger in using the $gp register to store a value? I guess my question is what is the true functionality of $gp and is it invoked behind-the-scenes somehow so that if I were to use it, things could go very very wrong? Thanks, Hristo

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• Memory allocation problem with SVMs in OpenCV

  - by worksintheory

  Hi, I've been using OpenCV happily for a while, but now I have a problem which has bugged me for quite some time. The following code is reasonably minimal example of my problem: #include <cv.h> #include <ml.h> using namespace cv; int main(int argc, char **argv) { int sampleCountForTesting = 2731; //BROKEN: Breaks svm.train_auto(...) for values of 2731 or greater! Mat trainingData( sampleCountForTesting, 1, CV_32FC1, Scalar::all(0.0) ); Mat trainingResponses( sampleCountForTesting, 1, CV_32FC1, Scalar::all(0.0) ); for(int j = 0; j < 6; j++) { trainingData.at<float>( j, 0 ) = (float) (j%2); trainingResponses.at<float>( j, 0 ) = (float) (j%2); //Setting a few values so I don't get a "single class" error } CvSVMParams svmParams( 100, //100 is CvSVM::C_SVC, 2, //2 is CvSVM::RBF, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, NULL, TermCriteria( TermCriteria::MAX_ITER | TermCriteria::EPS, 2, 1.0 ) ); CvSVM svm = CvSVM(); svm.train_auto( trainingData, trainingResponses, Mat(), Mat(), svmParams ); return 0; } I just create matrices to hold the training data and responses, then set a few entries to some value other than zero, then run the SVM. But it breaks whenever there are 2731 rows or more: OpenCV Error: One of arguments' values is out of range (requested size is negative or too big) in cvMemStorageAlloc, file [omitted]/opencv/OpenCV-2.2.0/modules/core/src/datastructs.cpp, line 332 With fewer rows, it seems to be fine and a classifier trained in a similar manner to the above seems to be giving reasonable output. Am I doing something wrong? I'm pretty sure it's not actually anything to do with lack of memory, as I've got 6GB and also the code works fine when the data has 2730 rows and 10000 columns, which is a much bigger allocation. I'm running OpenCV 2.2 on OSX 10.6 and initially I thought the problem might be related to this bug if for some reason the fix wasn't included in the MacPorts version. Now I've also tried downloading the most recent stable version from the OpenCV site and building with cmake and using that, but I still get the same error, and the fix is definitely included in that version. Any help would be much appreciated! Thanks,

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• NSXMLParser Memory Allocation Efficiency for the iPhone

  - by Staros

  Hello, I've recently been playing with code for an iPhone app to parse XML. Sticking to Cocoa, I decided to go with the NSXMLParser class. The app will be responsible for parsing 10,000+ "computers", all which contain 6 other strings of information. For my test, I've verified that the XML is around 900k-1MB in size. My data model is to keep each computer in an NSDictionary hashed by a unique identifier. Each computer is also represented by a NSDictionary with the information. So at the end of the day, I end up with a NSDictionary containing 10k other NSDictionaries. The problem I'm running into isn't about leaking memory or efficient data structure storage. When my parser is done, the total amount of allocated objects only does go up by about 1MB. The problem is that while the NSXMLParser is running, my object allocation is jumping up as much as 13MB. I could understand 2 (one for the object I'm creating and one for the raw NSData) plus a little room to work, but 13 seems a bit high. I can't imaging that NSXMLParser is that inefficient. Thoughts? Code... The code to start parsing... NSXMLParser *parser = [[NSXMLParser alloc] initWithData: data]; [parser setDelegate:dictParser]; [parser parse]; output = [[dictParser returnDictionary] retain]; [parser release]; [dictParser release]; And the parser's delegate code... -(void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict { if(mutableString) { [mutableString release]; mutableString = nil; } mutableString = [[NSMutableString alloc] init]; } -(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string { if(self.mutableString) { [self.mutableString appendString:string]; } } -(void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName { if([elementName isEqualToString:@"size"]){ //The initial key, tells me how many computers returnDictionary = [[NSMutableDictionary alloc] initWithCapacity:[mutableString intValue]]; } if([elementName isEqualToString:hashBy]){ //The unique identifier if(mutableDictionary){ [mutableDictionary release]; mutableDictionary = nil; } mutableDictionary = [[NSMutableDictionary alloc] initWithCapacity:6]; [returnDictionary setObject:[NSDictionary dictionaryWithDictionary:mutableDictionary] forKey:[NSMutableString stringWithString:mutableString]]; } if([fields containsObject:elementName]){ //Any of the elements from a single computer that I am looking for [mutableDictionary setObject:mutableString forKey:elementName]; } } Everything initialized and released correctly. Again, I'm not getting errors or leaking. Just inefficient. Thanks for any thoughts!

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• Remove never-run call to templated function, get allocation error on run-time

  - by Narfanator

  First off, I'm a bit at a loss as to how to ask this question. So I'm going to try throwing lots of information at the problem. Ok, so, I went to completely redesign my test project for my experimental core library thingy. I use a lot of template shenanigans in the library. When I removed the "user" code, the tests gave me a memory allocation error. After quite a bit of experimenting, I narrowed it down to this bit of code (out of a couple hundred lines): void VOODOO(components::switchBoard &board){ board.addComponent<using_allegro::keyInputs<'w'> >(); } Fundementally, what's weirding me out is that it appears that the act of compiling this function (and the template function it then uses, and the template functions those then use...), makes this bug not appear. This code is not being run. Similar code (the same, but for different key vals) occurs elsewhere, but is within Boost TDD code. I realize I certainly haven't given enough information for you to solve it for me; I tried, but it more-or-less spirals into most of the code base. I think I'm most looking for "here's what the problem could be", "here's where to look", etc. There's something that's happening during compile because of this line, but I don't know enough about that step to begin looking. Sooo, how can a (presumably) compilied, but never actually run, bit of templated code, when removed, cause another part of code to fail? Error: Unhandled exceptionat 0x6fe731ea (msvcr90d.dll) in Switchboard.exe: 0xC0000005: Access violation reading location 0xcdcdcdc1. Callstack: operator delete(void * pUser Data) allocator< class name related to key inputs callbacks ::deallocate vector< same class ::_Insert_n(...) vector< " " ::insert(...) vector<" "::push_back(...) It looks like maybe the vector isn't valid, because _MyFirst and similar data members are showing values of 0xcdcdcdcd in the debugger. But the vector is a member variable...

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• Tiny program to register work hours

  - by amin

  Hi dear ubuntu users. I'm searching for a tiny application to register my working hours so when I come to work and power on my pc it register my entrance and as a power off my pc it register me left. I know it's as simple as adding a note in gedit but I want it automated, phproject has a timer application as you start a task you push start and as you finish calculate time to register fot task , I'm searching for such small timer. thanks

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• Looking for a disk manager that has options for setting allocation sizes in paritions

  - by mango

  I'm looking for a GUI program that is compatible with Ubuntu 13.10 - Server X86-64 that has all the features of Gparted but also allows for setting custom allocation sizes when creating a partition. Eg: Ability to create a 4gb Fat32 parition with 32 kilobyte allocation size. Please don't suggest a terminal only application, no matter how awesome it might be, because that's not what I asked. Wow, I come off like a right up prick when I write, eh?

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• Objective-C object release and allocation timing

  - by ryanjm.mp

  The code for this question is too long to be of any use. But I'm pretty sure my problem has to do with releasing a class. I have a helper class, ConnectionHelper.h/.m, that handles a NSURLConnection for me. Basically, I give it the URL I want and it returns the data (it happens to do a quick json parse on it too). It has a delegate which I set to the calling class (in this case: DownloadViewController). When it finishes the download, it calls [delegate didFinishParseOf:objectName withDictionary:dictionary];. Then in DownloadViewController I release ConnectionHelper and alloc a new one in order to download the next object. My problem is, I do this once, and then it creates the connection for the second one, and then my program just crashes. After this call: [[NSHTTPCookieStorage sharedHTTPCookieStorage] setCookieAcceptPolicy:NSHTTPCookieAcceptPolicyNever]; NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self]; Then I don't think any of the following methods are called: - (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error - (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge So am I right in that I'm not releasing something? When I release it the first time, the dealloc function isn't being called. Is there a way I can "force" it to deallocate? Do I need to force it to? I didn't think it would matter since I allocating a new ConnectionHelper for the new call. How else would they overlap / conflict with each other? Thank you.

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• Memory allocation included in API

  - by gurugio

  If there is the 'struct foo' and an APIs which handle foo, which is more flexible and convenient API? 1) API only initialize foo. User should declare foo or allocate memory for foo. The this style is like pthread_mutex_init/pthread_mutex_destroy. example 1) struct foo a; init_foo(&a);' example 2) struct foo *a; a = malloc(sizeof(struct foo)); init_foo(a); 2) API allocates memory and user get the pointer. This is like getaddrinfo/freeaddrinfo. example) struct foo *a; get_foo(&a); put_foo(a);

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• Stack Allocation in C

  - by JT

  Is it bad style to design your simple C programs to allocate everything, or most everything, on the stack?

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• Private member vector of vector dynamic memory allocation

  - by Geoffroy

  Hello, I'm new to C++ (I learned programming with Fortran), and I would like to allocate dynamically the memory for a multidimensional table. This table is a private member variable : class theclass{ public: void setdim(void); private: std::vector < std::vector <int> > thetable; } I would like to set the dimension of thetable with the function setdim(). void theclass::setdim(void){ this->thetable.assign(1000,std::vector <int> (2000)); } I have no problem compiling this program, but as I execute it, I've got a segmentation fault. The strange thing for me is that this piece (see under) of code does exactly what I want, except that it doesn't uses the private member variable of my class : std::vector < std::vector < int > > thetable; thetable.assign(1000,std::vector <int> (2000)); By the way, I have no trouble if thetable is a 1D vector. In theclass : std::vector < int > thetable; and if in setdim : this->thetable.assign(1000,2); So my question is : why is there such a difference with "assign" between thetable and this-thetable for a 2D vector? And how should I do to do what I want? Thank-you for your help, Best regards, -- Geoffroy

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• C dynamic memory allocation for table of structs

  - by JosiP

  Hi here is my code. I want to dynamincly change no of elemnts in table with structs __state: typedef struct __state{ long int timestamp; int val; int prev_value; }*state_p, state_t; int main(int argc, char **argv){ int zm; int previous_state = 0; int state = 0; int i = 0; int j; state_p st; //here i want to have 20 structs st. st = (state_p) malloc(sizeof(state_t) * 20); while(1){ previous_state = state; scanf("%d", &state); printf("%d, %d\n", state, previous_state); if (previous_state != state){ printf("state changed %d %d\n", previous_state, state); // here i got compile error: main.c: In function ‘main’: main.c:30: error: incompatible type for argument 1 of ‘save_state’ main.c:34: error: invalid type argument of ‘->’ main.c:34: error: invalid type argument of ‘->’ save_state(st[i],previous_state, state); } i++; } return 0; } I suppose i have to change that st[i] to smth like st+ptr ? where pointer is incermeting in each loop iteration ? Or am I wrong ? When i change code: initialization into state_p st[20] and in each loop iteration i put st[i] = (state_p)malloc(sizeof(state_t)) everything works fine, but i want to dynammicly change number of elemets in that table. Thx in advance for any help

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• Dynamic stack allocation in C++

  - by Poni

  I want to allocate memory on the stack. Heard of _alloca / alloca and I understand that these are compiler-specific stuff, which I don't like. So, I came-up with my own solution (which might have it's own flaws) and I want you to review/improve it so for once and for all we'll have this code working: /*#define allocate_on_stack(pointer, size) \ __asm \ { \ mov [pointer], esp; \ sub esp, [size]; \ }*/ /*#define deallocate_from_stack(size) \ __asm \ { \ add esp, [size]; \ }*/ void test() { int buff_size = 4 * 2; char *buff = 0; __asm { // allocate mov [buff], esp; sub esp, [buff_size]; } // playing with the stack-allocated memory for(int i = 0; i < buff_size; i++) buff[i] = 0x11; __asm { // deallocate add esp, [buff_size]; } } void main() { __asm int 3h; test(); } Compiled with VC9. What flaws do you see in it? Me for example, not sure that subtracting from ESP is the solution for "any kind of CPU". Also, I'd like to make the commented-out macros work but for some reason I can't.

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• Class members allocation on heap/stack? C++

  - by simplebutperfect

  If a class is declared as follows: class MyClass { char * MyMember; MyClass() { MyMember = new char[250]; } ~MyClass() { delete[] MyMember; } }; And it could be done like this: class MyClass { char MyMember[250]; }; How does a class gets allocated on heap, like if i do MyClass * Mine = new MyClass(); Does the allocated memory also allocates the 250 bytes in the second example along with the class instantiation? And will the member be valid for the whole lifetime of MyClass object? As for the first example, is it practical to allocate class members on heap?

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• Understanding C++ dynamic allocation

  - by kiokko89

  Consider the following code: class CString { private: char* buff; size_t len; public: CString(const char* p):len(0), buff(nullptr) { cout << "Constructor called!"<<endl; if (p!=nullptr) { len= strlen(p); if (len>0) { buff= new char[len+1]; strcpy_s(buff, len+1, p); } } } CString (const CString& s) { cout << "Copy constructor called!"<<endl; len= s.len; buff= new char[len+1]; strcpy_s(buff, len+1, s.buff); } CString& operator = (const CString& rhs) { cout << "Assignment operator called!"<<endl; if (this != &rhs) { len= rhs.len; delete[] buff; buff= new char[len+1]; strcpy_s(buff, len+1, rhs.buff); } return *this; } CString operator + (const CString& rhs) const { cout << "Addition operator called!"<<endl; size_t lenght= len+rhs.len+1; char* tmp = new char[lenght]; strcpy_s(tmp, lenght, buff); strcat_s(tmp, lenght, rhs.buff); return CString(tmp); } ~CString() { cout << "Destructor called!"<<endl; delete[] buff; } }; int main() { CString s1("Hello"); CString s2("World"); CString s3 = s1+s2; } My problem is that I don't know how to delete the memory allocated in the addition operator function(char* tmp = new char[length]). I couldn't do this in the constructor(I tried delete[] p) because it is also called from the main function with arrays of chars as parameters which are not allocated on the heap...How can I get around this? (Sorry for my bad English...)

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• C vs. C++ for performance in memory allocation

  - by Andrei

  Hi, I am planning to participate in development of a code written in C language for Monte Carlo analysis of complex problems. This codes allocates huge data arrays in memory to speed up its performance, therefore the author of the code has chosen C instead of C++ claiming that one can make faster and more reliable (concerning memory leaks) code with C. Do you agree with that? What would be your choice, if you need to store 4-16 Gb of data arrays in memory during calculation?

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• C# memory allocation

  - by user279691

  Does using operator new in c# might fail (if it requires a large memory)? -Solved- And how to discover it? -Solved- What other failures new operator might throw? Thanks

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• Memory allocation in Linux

  - by Goofy

  Hello! I have a multi threaded application where I allocate buffers with data, which then wait in queues to be send via sockets. All buffers are reproducible because I use only buffers of fixed size in whole program (1024, 2048, 2080 and 5248 bytes). I noticed, that my program usually use up to 10 buffers of each length type at the same moment. So far I always manually allocate new buffer and then free it (using malloc() and free ()) where it's not needed any more. I started wondering if Linux is enough smart to cache this memory for me, so next time I allocate new buffer system only quickly receive a buffer I have already used before and not perform heavy operation of allocating new memory block?

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• C++ Dynamic Allocation Mismatch: Is this problematic?

  - by acanaday

  I have been assigned to work on some legacy C++ code in MFC. One of the things I am finding all over the place are allocations like the following: struct Point { float x,y,z; }; ... void someFunc( void ) { int numPoints = ...; Point* pArray = (Point*)new BYTE[ numPoints * sizeof(Point) ]; ... //do some stuff with points ... delete [] pArray; } I realize that this code is atrociously wrong on so many levels (C-style cast, using new like malloc, confusing, etc). I also realize that if Point had defined a constructor it would not be called and weird things would happen at delete [] if a destructor had been defined. Question: I am in the process of fixing these occurrences wherever they appear as a matter of course. However, I have never seen anything like this before and it has got me wondering. Does this code have the potential to cause memory leaks/corruption as it stands currently (no constructor/destructor, but with pointer type mismatch) or is it safe as long as the array just contains structs/primitive types?

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• c: memory allocation (what's going on)

  - by facha

  Hi, everyone Please take a look at this piece of code. I'm allocating one byte for the first variable and another byte for the second one. However, it seems like the compiler allocates more (or I'm missing something). The program outputs both strings, even though their length is more the one byte. void main() { char* some1 = malloc(1); sprintf(some1,"cool"); char* some2 = malloc(1); sprintf(some2,"face"); printf("%s ",some1); printf("%s\n",some2); } Please, could anyone spot some light on what's going on when memory is being allocated.

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• C++ new memory allocation fragmentation

  - by tamulj

  I was trying to look at the behavior of the new allocator and why it doesn't place data contiguously. My code: struct ci { char c; int i; } template <typename T> void memTest() { T * pLast = new T(); for(int i = 0; i < 20; ++i) { T * pNew = new T(); cout << (pNew - pLast) << " "; pLast = pNew; } } So I ran this with char, int, ci. Most allocations were a fixed length from the last, sometimes there were odd jumps from one available block to another. sizeof(char) : 1 Average Jump: 64 bytes sizeof(int): 4 Average Jump: 16 sizeof(ci): 8 (int has to be placed on a 4 byte align) Average Jump: 9 Can anyone explain why the allocator is fragmenting memory like this? Also why is the jump for char so much larger then ints and a structure that contains both an int and char.

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• C++ Memory allocation question involving vectors

  - by TheFuzz

  vector< int > vect; int *int_ptr = new int(10); vect.push_back( *int_ptr ); I under stand that every "new" needs to be followed by a "delete" at some point but does the clear() method clean this memory? What about this method of doing the same thing: vector< int > vect; int int_var = 10; vect.push_back( int_var ); From what I understand, clear() calls the variables destructors, but both vect.push_back() methods in this example push an object on the vector, not a pointer. so does the first example using an int pointer need something other than clear() to clean up memory?

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