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• Volatile fields in C#

  - by Danny Chen

  From the specification 10.5.3 Volatile fields: The type of a volatile field must be one of the following: A reference-type. The type byte, sbyte, short, ushort, int, uint, char, float, bool, System.IntPtr, or System.UIntPtr. An enum-type having an enum base type of byte, sbyte, short, ushort, int, or uint. First I want to confirm my understanding is correct: I guess the above types can be volatile because they are stored as a 4-bytes unit in memory(for reference types because of its address), which guarantees the read/write operation is atomic. A double/long/etc type can't be volatile because they are not atomic reading/writing since they are more than 4 bytes in memory. Is my understanding correct? And the second, if the first guess is correct, why a user defined struct with only one int field in it(or something similar, 4 bytes is ok) can't be volatile? Theoretically it's atomic right? Or it's not allowed simply because that all user defined structs(which is possibly more than 4 bytes) are not allowed to volatile by design?

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• Elegant way of parsing Data files for Simulation

  - by sc_ray

  I am working on this project where I need to read in a lot of data from .dat files and use the data to perform simulations. The data in my .dat file looks as follows: DeviceID InteractingDeviceID InteractionStartTime InteractionEndTime 1 2 1101 1105 1,2 1101 and 1105 are tab delimited and it means Device 1 interacted with Device 2 at 1101 ms and ended the interaction at 1105ms. I have a trace data sets that compile thousands of such interactions and my job is to analyze these interactions. The first step is to parse the file. The language of choice is C++. The approach I was thinking of taking was to read the file, for every line that's read create a Device Object. This Device object will contain the property DeviceId and an array/vector of structs, that will contain a list of all the devices the given DeviceId interacted with over the course of the simulation.The struct will contain the Interacting Device Id, Interaction Start Time and Interaction End Time. I have a two fold question here: Is my approach correct? If I am on the right track, how do I rapidly parse these tab delimited data files and create Device objects without excessive memory overhead using C++? A push in the right direction will be much appreciated. Thanks

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• Using unset member variables within a class or struct

  - by Doug Kavendek

  It's pretty nice to catch some really obvious errors when using unset local variables or when accessing a class or struct's members directly prior to initializing them. In visual studio 2008 you get an "uninitialized local variable used" warning at compile-time and get a run-time check failure at the point of access when debugging. However, if you access an uninitialized struct's member variable through one of its functions, you don't get any warnings or assertions. Obviously the easiest solution is don't do that, but nobody's perfect. For example: struct Test { float GetMember() const { return member; } float member; }; Test test; float f1 = test.member; // Raises warning, asserts in VS debugger at runtime float f2 = test.GetMember(); // No problem, just keeps on going This surprised me, but it makes some sense -- the compiler can't assume calling a function on an unused struct is an error, or how else would you initialize or construct it? And anything fancier just quickly brings up so many other complications that it makes sense that it wouldn't bother classifying which functions are ok to call and when, especially just as a debugging help. I know I can set up my own assertions or error checking within the class itself, but that can complicate some simpler structs. Still, it would seem like within the context of the function call, wouldn't it know insides GetMember() that member wasn't initialized yet? I'm assuming it's not only relying on static compile-time deduction, given the Run-Time Check Failure #3 it raises during execution, so based on my current understanding of it it would seem reasonable for the same checks to apply. Is this just a limitation of this specific compiler/debugger (Visual Studio 2008), or more tied to how C++ works?

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• Tips on designing a .NET API for future use with F#

  - by Drew Noakes

  I'm in the process of designing a .NET API to allow developers to create RoboCup agents for the 3D simulated soccer league. I'm pretty happy with how the API work with C# code, however I would like to use this project to improve my F# skill (which is currently based on reading rather than practice). So I would like to ask what kinds of things I should consider when designing an API that is to be consumed by both C# and F# code. Some points. I make fairly heavy use of matrix and vector math. These are currently immutable classes/structs. The API currently defines a few interfaces with the consumer implements (eg: IAgent), using instances of their implementations (eg: MyAgent) to construct other API classes (eg: new Client(myAgent)). The API fires events. The API exposes a few delegate types. The API includes several enums. I'd like to release a version of the API as soon as possible and don't want to make major changes to it later if I realise it's too difficult to work with from F#. Any advice is appreciated.

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• Passing Derived Class Instances as void* to Generic Callbacks in C++

  - by Matthew Iselin

  This is a bit of an involved problem, so I'll do the best I can to explain what's going on. If I miss something, please tell me so I can clarify. We have a callback system where on one side a module or application provides a "Service" and clients can perform actions with this Service (A very rudimentary IPC, basically). For future reference let's say we have some definitions like so: typedef int (*callback)(void*); // This is NOT in our code, but makes explaining easier. installCallback(string serviceName, callback cb); // Really handled by a proper management system sendMessage(string serviceName, void* arg); // arg = value to pass to callback This works fine for basic types such as structs or builtins. We have an MI structure a bit like this: Device <- Disk <- MyDiskProvider class Disk : public virtual Device class MyDiskProvider : public Disk The provider may be anything from a hardware driver to a bit of glue that handles disk images. The point is that classes inherit Disk. We have a "service" which is to be notified of all new Disks in the system, and this is where things unravel: void diskHandler(void *p) { Disk *pDisk = reinterpret_cast<Disk*>(p); // Uh oh! // Remainder is not important } SomeDiskProvider::initialise() { // Probe hardware, whatever... // Tell the disk system we're here! sendMessage("disk-handler", reinterpret_cast<void*>(this)); // Uh oh! } The problem is, SomeDiskProvider inherits Disk, but the callback handler can't receive that type (as the callback function pointer must be generic). Could RTTI and templates help here? Any suggestions would be greatly appreciated.

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• Deleting a node from linked list in C

  - by LuckySlevin

  My problem is deleting a node from linked list. I have two structs : typedef struct inner_list { int count; char word[100]; inner_list*next; } inner_list; typedef struct outer_list { char word [100]; inner_list * head; int count; outer_list * next; } outer_list; My problem is in deleting a node from outer_list linked list. For example when user entered aaa to delete, delete function should find the node with outer_list->word = aaa and delete this node and reconnect the list again. I tried the below code to do this. but After finding and deleting I'm losing the list. I don't know what's wrong. Please notice that outer_list have also a linked list of inner_list inside. void delnode(outer_list *head,char num[100]) { outer_list *temp, *m; temp=head; while(temp!=NULL) { if(strcmp(temp->word==num)==0) { if(temp==head) { head=temp->next; free(temp); return; } else { m->next=temp->next; free(temp); return; } }else { m=temp; temp= temp->next; } } printf(" ELEMENT %s NOT FOUND ", num); } What are your ideas about this?

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• Exporting WPF DataGrid to a text file in a nice looking format. Text file must be easy to read.

  - by Andrew

  Hi, Is there a simple way to export a WPF DataGrid to a text file and a .csv file? I've done some searching and can't see that there is a simple DataGrid method to do so. I have got something working (barely) by making use of the ItemsSource of the DataGrid. In my case, this is an array of structs. I do something with StreamWriters and StringBuilders (details available) and basically have: StringBuilder destination = new StringBuilder(); destination.Append(row.CreationDate); destination.Append(seperator); // seperator is '\t' or ',' for csv file destination.Append(row.ProcId); destination.Append(seperator); destination.Append(row.PartNumber); destination.Append(seperator); I do this for each struct in the array (in a loop). This works fine. The problem is that it's not easy to read the text file. The data can be of different lengths within the same column. I'd like to see something like: 2007-03-03 234238423823 823829923 2007-03-03 66 99 And of course, I get something like: 2007-03-03 234238423823 823829923 2007-03-03 66 99 It's not surprising giving that I'm using Tab delimiters, but I hope to do better. It certainly is easy to read in the DataGrid! I could of course have some logic to pad short values with spaces, but that seems quite messy. I thought there might be a better way. I also have a feeling that this is a common problem and one that has probably been solved before (hopefully within the .NET classes themselves). Thanks.

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• Interchange structured data between Haskell and C

  - by Eonil

  First, I'm a Haskell beginner. I'm planning integrating Haskell into C for realtime game. Haskell does logic, C does rendering. To do this, I have to pass huge complexly structured data (game state) from/to each other for each tick (at least 30 times per second). So the passing data should be lightweight. This state data may laid on sequential space on memory. Both of Haskell and C parts should access every area of the states freely. In best case, the cost of passing data can be copying a pointer to a memory. In worst case, copying whole data with conversion. I'm reading Haskell's FFI(http://www.haskell.org/haskellwiki/FFICookBook#Working_with_structs) The Haskell code look specifying memory layout explicitly. I have a few questions. Can Haskell specify memory layout explicitly? (to be matched exactly with C struct) Is this real memory layout? Or any kind of conversion required? (performance penalty) If Q#2 is true, Any performance penalty when the memory layout specified explicitly? What's the syntax #{alignment foo}? Where can I find the document about this? If I want to pass huge data with best performance, how should I do that? *PS Explicit memory layout feature which I said is just C#'s [StructLayout] attribute. Which is specifying in-memory position and size explicitly. http://www.developerfusion.com/article/84519/mastering-structs-in-c/ I'm not sure Haskell has matching linguistic construct matching with fields of C struct.

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• C#. How to pass message from unsafe callback to managed code?

  - by maxima120

  Is there a simple example of how to pass messages from unsafe callback to managed code? I have a proprietary dll which receives some messages packed in structs and all is coming to a callback function. The example of usage is as follows but it calls unsafe code too. I want to pass the messages into my application which is all managed code. *P.S. I have no experience in interop or unsafe code. I used to develop in C++ 8 yrs ago but remember very little from that nightmarish times :) P.P.S. The application is loaded as hell, the original devs claim it processes 2mil messages per sec.. I need a most efficient solution.* static unsafe int OnCoreCallback(IntPtr pSys, IntPtr pMsg) { // Alias structure pointers to the pointers passed in. CoreSystem* pCoreSys = (CoreSystem*)pSys; CoreMessage* pCoreMsg = (CoreMessage*)pMsg; // message handler function. if (pCoreMsg->MessageType == Core.MSG_STATUS) OnCoreStatus(pCoreSys, pCoreMsg); // Continue running return (int)Core.CALLBACKRETURN_CONTINUE; } Thank you.

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• How do I cast a void pointer to a struct in C?

  - by Rowhawn

  In a project I'm writing code for, I have a void pointer, "implementation", which is a member of a "Hash_map" struct, and points to an "Array_hash_map" struct. The concepts behind this project are not very realistic, but bear with me. The specifications of the project ask that I cast the void pointer "implementation" to an "Array_hash_map" before I can use it in any functions. My question, specifically is, what do I do in the functions to cast the void pointers to the desired struct? Is there one statement at the top of each function that casts them or do I make the cast every time I use "implementation"? Here are the typedefs the structs of a Hash_map and Array_hash_map as well as a couple functions making use of them. typedef struct { Key_compare_fn key_compare_fn; Key_delete_fn key_delete_fn; Data_compare_fn data_compare_fn; Data_delete_fn data_delete_fn; void *implementation; } Hash_map; typedef struct Array_hash_map{ struct Unit *array; int size; int capacity; } Array_hash_map; typedef struct Unit{ Key key; Data data; } Unit; functions: /* Sets the value parameter to the value associated with the key parameter in the Hash_map. */ int get(Hash_map *map, Key key, Data *value){ int i; if (map == NULL || value == NULL) return 0; for (i = 0; i < map->implementation->size; i++){ if (map->key_compare_fn(map->implementation->array[i].key, key) == 0){ *value = map->implementation->array[i].data; return 1; } } return 0; } /* Returns the number of values that can be stored in the Hash_map, since it is represented by an array. */ int current_capacity(Hash_map map){ return map.implementation->capacity; }

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• Do all C compilers allow functions to return structures?

  - by Jordan S

  I am working on a program in C and using the SDCC compiler for a 8051 architecture device. I am trying to write a function called GetName that will read 8 characters from Flash Memory and return the character array in some form. I know that it is not possible to return an array in C so I am trying to do it using a struct like this: //********************FLASH.h file******************************* MyStruct GetName(int i); //Function prototype #define NAME_SIZE 8 typedef struct { char Name[NAME_SIZE]; } MyStruct; extern MyStruct GetName(int i); // *****************FLASH.c file*********************************** #include "FLASH.h" MyStruct GetName( int i) { MyStruct newNameStruct; //... // Fill the array by reading data from Flash //... return newNameStruct; } I don't have any references to this function yet but for some reason, I get a compiler error that says "Function cannot return aggregate." Does this mean that my compiler does not support functions that return structs? Or am I just doing something wrong?

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• Integer array or struct array - which is better?

  - by MusiGenesis

  In my app, I'm storing Bitmap data in a two-dimensional integer array (int[,]). To access the R, G and B values I use something like this: // read: int i = _data[x, y]; byte B = (byte)(i >> 0); byte G = (byte)(i >> 8); byte R = (byte)(i >> 16); // write: _data[x, y] = BitConverter.ToInt32(new byte[] { B, G, R, 0 }, 0); I'm using integer arrays instead of an actual System.Drawing.Bitmap because my app runs on Windows Mobile devices where the memory available for creating bitmaps is severely limited. I'm wondering, though, if it would make more sense to declare a structure like this: public struct RGB { public byte R; public byte G; public byte B; } ... and then use an array of RGB instead of an array of int. This way I could easily read and write the separate R, G and B values without having to do bit-shifting and BitConverter-ing. I vaguely remember something from days of yore about byte variables being block-aligned on 32-bit systems, so that a byte actually takes up 4 bytes of memory instead of just 1 (but maybe this was just a Visual Basic thing). Would using an array of structs (like the RGB example` above) be faster than using an array of ints, and would it use 3/4 the memory or 3 times the memory of ints?

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• C# struct with object as data member

  - by source-energy

  As we know, in C# structs are passed by value, not by reference. So if I have a struct with the following data members: private struct MessageBox { // data members private DateTime dm_DateTimeStamp; // a struct type private TimeSpan dm_TimeSpanInterval; // also a struct private ulong dm_MessageID; // System.Int64 type, struct private String dm_strMessage; // an object (hence a reference is stored here) // more methods, properties, etc ... } So when a MessageBox is passed as a parameter, a COPY is made on the stack, right? What does that mean in terms of how the data members are copied? The first two are struct types, so copies should be made of DateTime and TimeSpan. The third type is a primitive, so it's also copied. But what about the dm_strMessage, which is a reference to an object? When it's copied, another reference to the same String is created, right? The object itself resides in the heap, and is NOT copied (there is only one instance of it on the heap.) So now we have to references to the same object of type String. If the two references are accessed from different threads, it's conceivable that the String object could be corrupted by being modified from two different directions simultaneously. The MSDN documentation says that System.String is thread safe. Does that mean that the String class has a built-in mechanism to prevent an object being corrupted in exactly the type of situation described here? I'm trying to figure out if my MessageBox struct has any potential flaws / pitfalls being a structure vs. a class. Thanks for any input. Source.Energy.

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• Is it poor design to create objects that only execute code during the constructor?

  - by Curtix

  In my design I am using objects that evaluate a data record. The constructor is called with the data record and type of evaluation as parameters and then the constructor calls all of the object's code necessary to evaluate the record. This includes using the type of evaluation to find additional parameter-like data in a text file. There are in the neighborhood of 250 unique evaluation types that use the same or similar code and unique parameters coming from the text file. Some of these evaluations use different code so I benefit a lot from this model because I can use inheritance and polymorphism. Once the object is created there isn't any need to execute additional code on the object (at least for now) and it is used more like a struct; its kept on a list and 3 properties are used later. I think this design is the easiest to understand, code, and read. A logical alternative I guess would be using functions that return score structs, but you can't inherit from methods so it would make it kind of sloppy imo. I am using vb.net and these classes will be used in an asp.net web app as well as in a distributed app. thanks for your input

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• Working with fields which can mutate or be new instances altogether

  - by dotnetdev

  Structs are usually used for immutable data, eg a phone number, which does not mutate, but instead you get a new one (eg the number 000 becoming 0001 would mean two seperate numbers). However, pieces of information like Name, a string, can either mutate (company abc changing its name to abcdef, or being given a new name like def). For fields like this, I assume they should reside in the mutable class and not an immutable structure? My way of structuring code is to have an immutable concept, like Address (any change is a new address completely), in a struct and then reference it from a class like Customer, since Customer always has an address. So I would put CompanyName, or Employer, in the class as it is mutable. But a name can either mutate and so be the same 1 instance, or a new name setup and while the company still owning the first name too. Would the correct pattern for assigning a new instance (eg a new company name but the old name still owned by the company) be?: string name = ""; string newName = new string(); newName = "new"; name = newName; And a mutation just the standard assignment pattern? Thanks

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• Accessing a struct collection property from within another collection

  - by paddyb

  I have a struct that I need to store in a collection. The struct has a property that returns a Dictionary. public struct Item { private IDictionary<string, string> values; public IDictionary<string, string> Values { get { return this.values ?? (this.values = new Dictionary<string, string>()); } } } public class ItemCollection : Collection<Item> {} When testing I've found that if I add the item to the collection and then try to access the dictionary the structs values property is never updated. var collection = new ItemCollection { new Item() }; // pre-loaded with an item collection[0].Values.Add("myKey", "myValue"); Trace.WriteLine(collection[0].Values["myKey"]); // KeyNotFoundException here However if I load up the item first and then add it to a collection the values field is maintained. var collection = new ItemCollection(); var item = new Item(); item.Values.Add("myKey", "myValue"); collection.Add(item); Trace.WriteLine(collection[0].Values["myKey"]); // ok I've already decided that a struct is the wrong option for this type, and when using a class the issue doesn't occur, but I'm curious what's different between the two methods. Can anybody explain what's happening?

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• How to cast C struct just another struct type if their memory size are equal?

  - by Eonil

  I have 2 matrix structs means equal data but have different form like these: // Matrix type 1. typedef float Scalar; typedef struct { Scalar e[4]; } Vector; typedef struct { Vector e[4]; } Matrix; // Matrix type 2 (you may know this if you're iPhone developer) struct CATransform3D { CGFloat m11, m12, m13, m14; CGFloat m21, m22, m23, m24; CGFloat m31, m32, m33, m34; CGFloat m41, m42, m43, m44; }; typedef struct CATransform3D CATransform3D; Their memory size are equal. So I believe there is a way to convert these types without any pointer operations or copy like this: // Implemented from external lib. CATransform3D CATransform3DMakeScale (CGFloat sx, CGFloat sy, CGFloat sz); Matrix m = (Matrix)CATransform3DMakeScale ( 1, 2, 3 ); Is this possible? Currently compiler prints an "error: conversion to non-scalar type requested" message.

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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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• Assigning a value to an integer in a C linked list

  - by Drunk On Java

  Hello all. I have a question regarding linked lists. I have the following structs and function for example. struct node { int value; struct node *next; }; struct entrynode { struct node *first; struct node *last; int length; }; void addnode(struct entrynode *entry) { struct node *nextnode = (struct node *)malloc(sizeof(struct node)); int temp; if(entry->first == NULL) { printf("Please enter an integer.\n"); scanf("%d", &temp); nextnode->value = temp; nextnode->next = NULL; entry->first = nextnode; entry->last = nextnode; entry->length++; } else { entry->last->next = nextnode; printf("Please enter an integer.\n"); scanf("%d", nextnode->value); nextnode->next = NULL; entry->last = nextnode; entry->length++; } } In the first part of the if statement, I store input into a temp variable and then assign that to a field in the struct. The else branch, I tried to assign it directly which did not work. How would I go about assigning it directly? Thanks for your time.

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• C# XML parsing with LINQ storing directly to a struct?

  - by Luke

  Say I have the following XML schema: <root> <version>2.0</version> <type>fiction</type> <chapters> <chapter>1</chapter> <title>blah blah</title> </chapter> <chapters> <chapter>2</chapter> <title>blah blah</title> </chapters> </root> Would it be possibly to parse the elements which I know will not be repeated in the XML and store them directly into the struct using LINQ? For example, could I do something like this for "version" and "type" //setup structs Book book = new Book(); book.chapter = new Chapter(); //use LINQ to parse the xml var bookData = from b in xmlDoc.Decendants("root") select new { book.version = b.Element("version").Value, book.type = b.Element("type").Value }; //then for "chapters" since I know there are multiple I can do: var chapterData = from c in xmlDoc.Decendants("root" select new { chapter = c.Element("chapters") }; foreach (var ch in chapterData) { book.chapter.Add(getChapterData(ch.chapter)); }

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• Operator overloading in generic struct: can I create overloads for specific kinds(?) of generic?

  - by Carson Myers

  I'm defining physical units in C#, using generic structs, and it was going okay until I got the error: One of the parameters of a binary operator must be the containing type when trying to overload the mathematical operators so that they convert between different units. So, I have something like this: public interface ScalarUnit { } public class Duration : ScalarUnit { } public struct Scalar<T> where T : ScalarUnit { public readonly double Value; public Scalar(double Value) { this.Value = Value; } public static implicit operator double(Scalar<T> Value) { return Value.Value; } } public interface VectorUnit { } public class Displacement : VectorUnit { } public class Velocity : VectorUnit { } public struct Vector<T> where T : VectorUnit { #... public static Vector<Velocity> operator /(Vector<Displacement> v1, Scalar<Duration> v2) { return new Vector<Velocity>(v1.Magnitude / v2, v1.Direction); } } There aren't any errors for the + and - operators, where I'm just working on a Vector<T>, but when I substitute a unit for T, suddenly it doesn't like it. Is there a way to make this work? I figured it would work, since Displacement implements the VectorUnit interface, and I have where T : VectorUnit in the struct header. Am I at least on the right track here? I'm new to C# so I have difficulty understanding what's going on sometimes.

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• Can a member struct be zero-init from the constructor initializer list without calling memset?

  - by selbie

  Let's say I have the following structure declaration (simple struct with no constructor). struct Foo { int x; int y; int z; char szData[DATA_SIZE]; }; Now let's say this struct is a member of a C++ class as follows: class CFoobar { Foo _foo; public: CFoobar(); }; If I declare CFoobar's constructor as follows: CFoobar::CFoobar() { printf("_foo = {%d, %d, %d}\n", _foo.x, _foo.y,_foo.z); for (int x = 0; x < 100; x++) printf("%d\n", _foo.szData[x]); } As you would expect, when CFoobar's constructor runs, garbage data gets printed out Obviously, the easy fix is to memset or ZeroMemory &_foo. It's what I've always done... However, I did notice that if add _foo to the constructor's initialization list with no parameters as follows: CFoobar::CFoobar() : _foo() { That this appears to zero-out the member variables of _foo. At least that was the case with g++ on linux. Now here's my question: Is this standard C++, or is this compiler specific behavior? If it's standard behavior, can someone quote me a reference from an official source? Any "gotchas" in regards to implicit zero-init behavior with more complicated structs and classes?

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• Overlaying several CLR reference fields with each other in explicit struct?

  - by thr

  Edit: I'm well aware of that this works very well with value types, my specific question is about using this for reference types. I've been tinkering around with structs in .NET/C#, and I just found out that you can do this: using System; using System.Runtime.InteropServices; namespace ConsoleApplication1 { class Foo { } class Bar { } [StructLayout(LayoutKind.Explicit)] struct Overlaid { [FieldOffset(0)] public object AsObject; [FieldOffset(0)] public Foo AsFoo; [FieldOffset(0)] public Bar AsBar; } class Program { static void Main(string[] args) { var overlaid = new Overlaid(); overlaid.AsObject = new Bar(); Console.WriteLine(overlaid.AsBar); overlaid.AsObject = new Foo(); Console.WriteLine(overlaid.AsFoo); Console.ReadLine(); } } } Basically circumventing having to do dynamic casting during runtime by using a struct that has an explicit field layout and then accessing the object inside as it's correct type. Now my question is: Can this lead to memory leaks somehow, or any other undefined behavior inside the CLR? Or is this a fully supported convention that is usable without any issues? I'm aware that this is one of the darker corners of the CLR, and that this technique is only a viable option in very few specific cases.

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• Why is joining two vectors simply not working?

  - by Jim

  I have two vectors of MyObj structs. MyObj is defined as follows: struct MyObj { float x, y; unsigned int data[8]; unsigned int tmp[1]; MyObj(const MyObj &m) { x = m.x; y = m.y; tmp[0] = 0; for (int i = 0; i < 8; ++i) { data[i] = m.data[i]; } } }; I then have two vectors... vector<MyObj> v1; vector<MyObj> v2; // both get data eventually. v1.insert(v1.end(), v2.begin(), v2.end()); v2 has 3535004 elements in my experiment. v1 is similarly sized. I've also tried building a new vector and just using .push_back to build it from both vectors. Essentially, when I try to merge the two vectors I just get an error from visual studio saying "Debug error! R6010, abort() has been called". Very non-useful... So my question is: what could be causing this error, and how can I solve it? Thank you

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• Receiving "expected expression before" Error When Using A Struct

  - by Zach Dziura

  I'm in the process of creating a simple 2D game engine in C with a group of friends at school. I'd like to write this engine in an Object-Oriented way, using structs as classes, function pointers as methods, etc. To emulate standard OOP syntax, I created a create() function which allocates space in memory for the object. I'm in the process of testing it out, and I'm receiving an error. Here is my code for two files that I'm using to test: test.c: #include <stdio.h> int main() { typedef struct { int i; } Class; Class *test = (Class*) create(Class); test->i = 1; printf("The value of \"test\" is: %i\n", test->i); return 0; } utils.c: #include <stdio.h> #include <stdlib.h> #include "utils.h" void* create(const void* class) { void *obj = (void*) malloc(sizeof(class)); if (obj == 0) { printf("Error allocating memory.\n"); return (int*) -1; } else { return obj; } } void destroy(void* object) { free(object); } The utils.h file simply holds prototypes for the create() and destroy() functions. When I execute gcc test.c utils.c -o test, I'm receiving this error message: test.c: In function 'main': test.c:10:32: error: expected expression before 'Class' I know it has something to do with my typedef at the beginning, and how I'm probably not using proper syntax. But I have no idea what that proper syntax is. Can anyone help?

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