header-files

There are two classes that are related to each other in their headers: PlotMarker #ifndef PLOTMARKER_H #define PLOTMARKER_H #include <QObject> #include "plotter.h" class Plotter; class PlotMarker : public QObject { // ... Plotter* m_attachedPlot; // ... }; #endif // PLOTMARKER_H Plotter #ifndef PLOTTER_H #define PLOTTER_H // ... #include "plotmarker.h" // ... class PlotMarker; class Plotter : public QQuickPaintedItem { // ... QLinkedList<PlotMarker*> m_markerList; // ... }; #endif // PLOTTER_H The program is compiled well, but it's got a error error: unterminated conditional directive in

Hi I noticed if I include a header file in a .cpp then I can create an object of that header file's class. Like if I include A.h in main.cpp then I can write A *a; in main.cpp . But this doesn't work if I include a header file in another header file and then try to create the object of that included header file. Like, file B.h : #include "A.h" class B { public: B(){}; A *a; }; I have to add forward declaration of the class A to make it work. Why? Here are the basics: For any type A , if you declare a variable of type A& , A* , A** , A*** ,etc, then the compiler does not need to know the

I was wondering what were the default values of variables before I initialized them... For example, if I do : //myClass.h BOOL myBOOL; // default value ? NSArray *myArray; // default value ? NSUInteger myInteger; // default value ? Some more examples here : //myClass.m // myArray is not initialized, only declared in .h file if ([myArray count] == 0) { // TRUE or FALSE ? // do whatever } More generally, what is returned when I do : [myObjectOnlyDeclaredAndNotInitialized myCustomFunction]; Thank you for your answers. Gotye. The answer is that it depends on the scope in which the variable is

If I create a static library in C++ in Linux such that a ".a" file is produced, how do I (or anyone else) use the library? For example, my library defines a class. I assume that it is not sufficient merely to provide the ".a" file, but also to provide a header file. How do I know what header files must be provided with the ".a" file? For example, do I need to provide all header files that were included anywhere in the code for my library? Emilio Garavaglia The technical reason for header files is to let the compiler know about names and sizes while compiling user code, so that it can arrange

Is there a Win32 equivalent to the linux header file? I'm working on a Linux to Windows port (and my first time doing so) and it's failing on this file. When writing WIN32API apps you usually #include <windows.h> - that includes most of the Windows API in your application. If you need to cut down on some of those includes, #define WIN32_LEAN_AND_MEAN will wipe out some of the more obscure things from the Windows libraries. What functions are you trying to convert? It'll probably be a case of using a different function on WIN32; it is very different to Linux/Unix/POSIX. Example: the ReadFile()

#include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <unistd.h> #include <arpa/inet.h> #include <netdb.h> #include <unistd.h> #include <signal.h> #include <stdio.h> #include <string.h> #include <fcntl.h> #include <errno.h> #include <sys/time.h> #include <stdlib.h> #include <memory.h> #include <ifaddrs.h>#include <net/if.h> #include <stdarg.h> #define BACKLOG 10 void * get_in_addr(struct sockaddr *sa){ if(sa->sa_family == AF_INET){ return &((sockaddr_in *)sa)->sin_addr; } else if(sa->sa_family == AF_INET6){ return &((sockaddr_in6 *)sa)->sin6_addr; } } I am using the

Here's the error: In file included from /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/ios:39, from /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/ostream:40, from /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iostream:40, from date.h:15, from date.cpp:13: /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/bits/ios_base.h: In copy constructor ‘std::basic_ios<char, std::char_traits<char> >::basic_ios(const std::basic_ios<char, std::char_traits<char> >&)’: /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../..

There is a claim in Which headers in the C++ standard library are guaranteed to include another header? : The C++ standard library headers may include each other in unspecified ways, so programmers generally shouldn't depend on one header including another. [...] In practice this tends to be the case. For example, <iostream> may include <string> , in other cases you need to include <string> explicitly. However, I can't seem to find where in N4140 this is the case. I've looked in: §2.9 [lex.header] §17.6.1.2 [headers] §17.6.2.2 [using.headers] §17.6.4.4 [alt.headers] §17.6.5.2 [res.on.headers]