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Search found 976 results on 40 pages for 'typedef'.

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• pointers in C with a #define

  - by milan

  The function: #define ASSOC(port) (*(volatile bit_field *) (&port)) The function call: #define SCLK ASSOC(PORTC).bit0 bit_field defined as a struct like this: typedef struct { unsigned char bit0 :1, bit1 :1, bit2 :1, bit3 :1, bit4 :1, bit5 :1, bit6 :1, bit7 :1; } bit_field; I don't know where &port is defined. Can someone please explain how the function is read and how it works please? I am not very good with pointers and this example in particular is very confusing with "*" in the front and at the end and the "&" with the port. Thank you

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• C - add elements to struct by define

  - by CodeStepper

  I have a problem. I'm trying to add struct elements by previously defined constant. This is sample code (OpenGL+WinAPI) #define ENGINE_STRUCT \ HGLRC RenderingContext;\ HDC DeviceContext; And then: typedef struct SWINDOW { ENGINE_STRUCT HWND Handle; HINSTANCE Instance; CHAR* ClassName; BOOL Fullscreen; BOOL Active; MSG Message; } WINDOW; Is this possible? Thanks in advance.

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• Is 'bool' a basic datatype in C++ ?

  - by Naveen

  I got this doubt while writing some code. Is 'bool' a basic datatype defined in the C++ standard or is it some sort of extension provided by the compiler ? I got this doubt because Win32 has 'BOOL' which is nothing but a typedef of long. Also what happens if I do something like this: int i = true; Is it "always" guaranteed that variable i will have value 1 or is it again depends on the compiler I am using ? Further for some Win32 APIs which accept BOOL as the parameter what happens if I pass bool variable?

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• How do I iterate over a tuple

  - by Caligo

  How can I iterate over a tuple starting from, say, index 1 to 2? The following doesn't work. using boost::fusion::cons; typedef cons<A, cons<B, cons<C, cons<D> > > > MyTuple; MyTuple tuple_; template <class T> struct DoSomething{ DoSomething(T& t) : t_(&t){ } template <class U> void operator()(U u){ boost::fusion::at<mpl::int_<u> >(*t_); } T* t_; }; boost::mpl::for_each< boost::mpl::range_c<int, 1, 3> >( DoSomething<MyTuple>(tuple_) );

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• how to get stl map to construct/destruct inserted object only once.

  - by Alberto Toglia

  I have found a very prejudicial fact about stl maps. For some reason I cant get objects being inserted in the map to get constructed/destructed only once. Example: struct MyObject{ MyObject(){ cout << "constructor" << endl; } ~MyObject(){ cout << "destructor" << endl; } }; int main() { std::map<int, MyObject> myObjectsMap; myObjectsMap[0] = MyObject(); return 0; } returns: constructor destructor destructor constructor destructor If I do: typedef std::pair<int, MyObject> MyObjectPair; myObjectsMap.insert( MyObjectPair(0,MyObject())); returns: constructor destructor destructor destructor I'm inserting Objects responsible for their own memory allocation, so when destructed they'll clean themselves up, being destructed several times is causing me some trouble.

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• Reading a variable messes it up?!?!

  - by EpsilonVector

  We have the following line of code: printf("%d\n", toc->runlist.next); printf("%d\n", toc->runlist.next); These are the definitions: typedef struct thread_overview_control{ int id[NR_UTHREADS]; list_t runlist; int active_counter; int main_thread; int need_resched; } thread_overview_control; thread_overview_control* toc; What I'm trying to do is implement user threads. For some reason the output of the above code at the point where our test run crushes is: 12345678 //some address 0 //NOW IT'S NULL?!?!?! How can this happen?? All we do is read a variable. And the strange thing is, without printf's there are no crashes. What's going on?

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• How can I declare a pointer structure using {}?

  - by Y_Y

  This probably is one of the easiest question ever in C programming language... I have the following code: typedef struct node { int data; struct node * after; struct node * before; }node; struct node head = {10,&head,&head}; Is there a way I can make head to be *head [make it a pointer] and still have the availability to use '{ }' [{10,&head,&head}] to declare an instance of head and still leave it out in the global scope? For example: //not legal!!! struct node *head = {10,&head,&head};

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• C/C++ enums: Detect when multiple items map to same value

  - by Dan

  Is there a compile-time way to detect / prevent duplicate values within a C/C++ enumeration? The catch is that there are multiple items which are initialized to explicit values. Background: I've inherited some C code such as the following: #define BASE1_VAL (5) #define BASE2_VAL (7) typedef enum { MsgFoo1A = BASE1_VAL, // 5 MsgFoo1B, // 6 MsgFoo1C, // 7 MsgFoo1D, // 8 MsgFoo1E, // 9 MsgFoo2A = BASE2_VAL, // Uh oh! 7 again... MsgFoo2B // Uh oh! 8 again... } FOO; The problem is that as the code grows & as developers add more messages to the MsgFoo1x group, eventually it overruns BASE2_VAL. This code will eventually be migrated to C++, so if there is a C++-only solution (template magic?), that's OK -- but a solution that works with C and C++ is better.

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• Tools for understanding large codebase

  - by 0tar0gz

  Hi! My whole life I have been programming in simple plain text editor. Lately, I was contemplating about joining an open source project which is fairly large and written in C. I downloaded the sources, started to look around, read this, forget that... Then I thought to myself: this can't be true. This is 21st century there must be some tool which would help me to understand the code, perhaps some kind of IDE or "code navigator". What flows from here to where, this typedef struct is just interface to that private type, this function is just #define from above, function called in this file is defined in that file, ... you get the idea. Dear Stack Overflow, is this 21st century? Is there something like this?

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• C undefined reference to `some_foo'

  - by sterh

  Hello, I have 3 files in my gtk+ app: main.c: #include <gtk/gtk.h> #include <glib/gi18n.h> #include "mainwindow.h" int main(int argc, char** argv) { MainWin* win; GError* err = NULL; int a = 0; a = some_foo(); gtk_main(); return 0; } mainwindo.h #include <gtk/gtk.h> typedef struct _MainWin { GtkWindow parent; } MainWin; GtkWidget* main_win_new(); int some_foo(); MainWindow.c #include "mainwindow.h" int some_foo() { return 1; } When i try to call some_foo in main function, and try to compile i see error: undefined reference to `some_foo'. What's wrong? Thank you.

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• When convert a void pointer to a specific type pointer, which casting symbol is better, static_cast or reinterpret_cast?

  - by BugCreater

  A beginner question with poor English: Here I got a void* param and want to cast(or change) it to a specific type. But I don't know which "casting symbol" to use. Either**static_cast** and reinterpret_cast works. I want to know which one is better? which one does the Standard C++ recommend? typedef struct { int a; }A, *PA; int foo(void* a) // the real type of a is A* { A* pA = static_cast<A*>(a); // or A* pA = reinterpret_cast<A*>(a);? cout<<pA->a<<endl; return 0; } Here I use A* pA = static_cast(a); or A* pA = reinterpret_cast(a); is more proper?

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• Policies Array Class-Design wrapper

  - by PT

  Hi, i want to write an wrapper for different Array Classes with different Policies. For example: typedef ArrayType<useValArray,StdAllocator> Array; // one global assignment I want to use the class like a blitz++ Array for example: Array<double,2> x(2,2); //maps the Array to an Valarray or to a Blitz++ Array Array<double,2> x2(5,6); is this Posible? Which technics i need to realise that?

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• writing structs and classes to disk

  - by Phenom

  The following function writes a struct to a file. int btwrite(short rrn, BTPAGE *page_ptr) { long addr; addr = (long) rrn * (long) PAGESIZE + HEADERSIZE; lseek(btfd, addr, 0); return (write(btfd, page_ptr, PAGESIZE)); } The following is the struct. typedef struct { short keycount; /* number of keys in page */ int key[MAXKEYS]; /* the actual keys */ int value[MAXKEYS]; /* the actual values */ short child[MAXKEYS+1]; /* ptrs to rrns of descendants */ } BTPAGE; What would happen if I changed the struct to a class, would it still work the same? If I added class functions, would the size it takes up on disk increase?

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• Adapting Map Iterators Using STL/Boost/Lambdas

  - by John Dibling

  Consider the following non-working code: typedef map<int, unsigned> mymap; mymap m; for( int i = 1; i < 5; ++i ) m[i] = i; // 'remove' all elements from map where .second < 3 remove(m.begin(), m.end(), bind2nd(less<int>(), 3)); I'm trying to remove elements from this map where .second < 3. This obviously isn't written correctly. How do I write this correctly using: Standard STL function objects & techniques Boost.Bind C++0x Lambdas I know I'm not eraseing the elements. Don't worry about that; I'm just simplifying the problem to solve.

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• Why do you sometimes need to write <typename T> instead of just <T> ?

  - by StackedCrooked

  I was reading the Wikipedia article on SFINAE and encountered following code sample: struct Test { typedef int Type; }; template < typename T > void f( typename T::Type ) {} // definition #1 template < typename T > void f( T ) {} // definition #2 void foo() { f< Test > ( 10 ); //call #1 f< int > ( 10 ); //call #2 without error thanks to SFINAE } Now I've actually written code like this before, and somehow intuitively I knew that I needed to type "typename T" instead of just "T". However, it would be nice to know the actual logic behind it. Anyone care to explain?

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• Does this make any sense (Apple-documentation)?

  - by Paperflyer

  Here is a snippet of the official Apple Documentation of AudioBufferList (Core Audio Data Types Reference) AudioBufferList Holds a variable length array of AudioBuffer structures. struct AudioBufferList { UInt32 mNumberBuffers; AudioBuffer mBuffers[1]; }; typedef struct AudioBufferList AudioBufferList; Fields mNumberBuffers The number of AudioBuffer structures in the mBuffers array. mBuffers A variable length array of AudioBuffer structures. If mBuffers is defined as AudioBuffer[1] it is not of variable length and thus mNumberBuffers is implicitly defined as 1. Do I miss something here or is this just nonsense?

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• Typechecking macro arguments in C

  - by Rocketmagnet

  Hi all, Is is possible to typecheck arguments to a #define macro? For example: typedef enum { REG16_A, REG16_B, REG16_C }REG16; #define read_16(reg16) read_register_16u(reg16); \ assert(typeof(reg16)==typeof(REG16)); The above code doesn't seem to work. What am I doing wrong? BTW, I am using gcc, and I can guarantee that I will always be using gcc in this project. The code does not need to be portable.

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• assignment from incompatible pointer type

  - by Hristo

  I have set up the following struct: typedef struct _thread_node_t { pthread_t thread; struct thread_node_t *next; } thread_node_t; ... and then I have defined: // create thread to for incoming connection thread_node_t *thread_node = (thread_node_t*) malloc(sizeof(thread_node_t)); pthread_create(&(thread_node->thread), NULL, client_thread, &csFD); thread_node->next = thread_arr; // assignment from incompatible pointer type thread_arr = thread_node; where thread_arr is thread_node_t *thread_arr = NULL; I don't understand why the compiler is complaining. Maybe I'm misunderstanding something.

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• Compilation failing - no #include - boost

  - by jwoolard

  Hi, I'm trying to compile a third-party library, but g++ is complaining about the following line: typedef boost::shared_ptr<MessageConsumer> MessageConsumerPtr; The strange thing is, there is no #include directive in the file - and it is clearly supposed to be this way; there are about 60 files with the same (or very similar) issues. Clearly if there was an #include directive referencing the relevant boost header this would compile cleanly. My question is: how can I get g++ to somehow automagically find the relevant symbol (in all instances of this issue, it is a namespace that can't be found - usually std:: or boost::) by either automatically processing the relevant header (or some other mechanism). Thanks. Edit My current g++ call looks like: g++ -fPIC -O3 -DUSING_PCH -D_REENTRANT -I/usr/include/boost -I./ -c MessageInterpreter.cpp -o MessageInterpreter.o

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• iOS Development: How can I encapsulate a string in an NSData object?

  - by BeachRunnerJoe

  Hello. I'm building a multiplayer game on the iPhone and I need to send string data to the other players in the game. To do that, I need to encapsulate my NSString* string data in an NSData object somehow. Here's an example of how my code is structured... typedef struct { PACKETTYPE packetType; ??? stringToSend; //<---not sure how to store this } StringPacket; StringPacket msg; msg.packetType = STRING_PACKET; msg.stringToSend = ... // <---not sure what to do here NSData *packet = [NSData dataWithBytes:&msg length:sizeof(StringPacket)]; So my question is, if StringPacket is a struct defined in my header, what type should the stringToSend property be so that I can easily call the dataWithBytes method of NSData to encapsulate the packet data in an NSData object? Thanks for your wisdom!

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• Stucture with array of pointers in C

  - by MVTCplusplus

  What's wrong with this? Can I have an array of pointers to SDL_Surfaces in a struct in C? typedef struct { int next_wheel; int pos_X; int pos_Y; int front_wheel_pos_X; int front_wheel_pos_Y; int velocity; int rear_wheel_pos_X; int rear_wheel_pos_Y; SDL_Surface* body; SDL_Surface* rear_wheel[9]; SDL_Surface* front_wheel[9]; } mars_rover; ... mars_rover* init_rover() { mars_rover* rover = (mars_rover*)malloc(sizeof(mars_rover) + sizeof(SDL_Surface) * 19); ... return rover; } int main() { mars_rover* rover = init_rover(); ... }

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• Redundant naming in C/C++ typedefs/structs

  - by bloomy

  #include <stdio.h> #include <string.h> const int NAMELEN=30; const int MAXCLASSSIZE=10; typedef struct StudentRec { char lastname[NAMELEN]; char firstname[NAMELEN]; long int ID; int finalmark; }Student; I'm new to coding..and I have a question about why there is Student; after the bracket.. is it a format that we have to follow.

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• Cast A primitive type pointer to A structure pointer - Alignment and Padding?

  - by Seçkin Savasçi

  Just 20 minutes age when I answered a question, I come up with an interesting scenario that I'm not sure of the behavior: Let me have an integer array of size n, pointed by intPtr; int* intPtr; and let me also have a struct like this: typedef struct { int val1; int val2; //and less or more integer declarations goes on like this(not any other type) }intStruct; My question is if I do a cast intStruct* structPtr = (intStruct*) intPtr; Am I sure to get every element correctly if I traverse the elements of the struct? Is there any possibility of miss-alignment(possible because of padding) in any architecture/compiler?

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• Why does this C++ char array seem to be able to hold more than its size?

  - by Phenom

  #include <iostream> using namespace std; typedef struct { char streetName[5]; } RECORD; int main() { RECORD r; cin >> r.streetName; cout << r.streetName << endl; } When I run this program, if I enter in more than 5 characters, the output will show the whole string I entered. It does not truncate at 5 characters. Why is that? How can I get this to work correctly?

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• How do I unpack bits from a structure's stream_data in c code?

  - by Chelp

  Ex. typedef struct { bool streamValid; dword dateTime; dword timeStamp; stream_data[800]; } RadioDataA; Ex. Where stream_data[800] contains: **Variable** **Length (in bits)** packetID 8 packetL 8 versionMajor 4 versionMinor 4 radioID 8 etc.. I need to write: void unpackData(radioDataA *streamData, MA_DataA *maData) { //unpack streamData (from above) & put some of the data into maData //How do I read in bits of data? I know it's by groups of 8 but I don't understand how. //MAData is also a struct. }

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