c extern

Analysis on the usage of http://www.cnblogs.com/rollenholt/archive/2012/03/20/2409046.htmlextern "C" 1. IntroductionC ++ language was originally created as "a better C ", however, this does not mean that the compilation and connection methods used by global variables and functions similar to C in C ++ are the same as those in C. As a language to be compatible with C, C ++ retains the features of some procedural languages (known as "not completely oriented objects "), therefore, it can define glo

1. Basic explanationExternIt can be placed before a variable or function to indicate that the definition of a variable or function is in another file, prompting the compiler to find its definition in other modules when it encounters this variable and function. In addition,ExternYou can also specify links. 2 problem: the extern variable defines an array in a source file: Char A [6]. In another file, it is declared using the following statement:

Extern usage and extern usage In C, the modifier extern is used before the declaration of a variable or function to indicate that "this variable/function is defined elsewhere and must be referenced here ". (Extern can be placed before a variable or function to indicate that the definition of a variable or function is i

Explanation of the functions of extern C and extern The main function of extern "C" is to call other C code correctly. After extern "C" is added, it indicates that the code of the compiler is compiled in C language instead of C ++. C ++ supports function overloading. Therefore, during function compilation, the paramete

Extern "C" Usage Analysis, extern Usage Analysis Extern "c" Usage Analysis AuthorAuthor Jason Ding, Link http://www.jianshu.com/p/5d2eeeb93590 IntroductionC ++ retains the features of some procedural languages, so it can define global variables and functions that do not belong to any class. However, C ++ is an object-oriented programming language after all. To s

Explanation of the extern keyword in C/C ++ and the extern keyword1. Basic explanation 　　ExternCan be placed inVariableOrBefore FunctionTo indicateDefinitionInOther filesWhen the compiler encounters this variable and function, it is prompted to find its definition in other modules. In addition, extern can also be usedLink specified. That is to say,

extern is a keyword that tells the compiler that there is a variable or function, and that if no corresponding variable or function is found, it is defined in the current file or file to see an example: #include At this point the compilation will be faulted: ' I ': Indetifier not Fonud ' func ': identifier not found The variables I and Func in the code above are defined at the end of the file, and the compiler is defined from the top down, when Func a

1 Basic explanationsextern can be placed before a variable or function to mark the definition of a variable or function in another file, prompting the compiler to find its definition in other modules when it encounters this variable and function.In addition, extern can also be used for link designation. 2 Question: extern variableAn array is defined in a source file: Char a[6];In another file, it is declare

1. Basic explanation Extern can be placed before a variable or function to indicate that the definition of a variable or function is in another file, prompting the compiler to find its definition in other modules when it encounters this variable or function. In addition, extern can be used to specify links. 2 problem: extern variable An array is defined in a sour

http://www.geeksforgeeks.org/extern-c-in-c/C + + functions overload (function overloading), but how does the C + + compiler distinguish between different functions? ----is by adding some information in the function name to a different function, the so-called name mangling. The C + + standard does not have a name mangling technology, and each compiler can add different information.Consider the following functionint F (voidreturn1;} int F (int) retur

limits the scope within this module (file).The advantage of using internal functions is that different people write different functions without worrying about the functions they define, or whether they have the same name as functions in other files. extern variable External variables are defined outside the program, and all functions are available in the program segment. The external variable may be redefined in one of the program segments, with the

The principle of implementing the C ++ function overload and why the extern "C" statement must be added when calling a function compiled by C language in C ++ to overload the extern Compared with C, function Overloading is a major feature of C ++, I believe that when using the C language, if you want to write a function to add two integer data and a floating point data addition function, the names of these

defined in B } B.cpp int i; The results of the compilation are as follows: Compiling ... A.cpp C:\Documents and settings\wangjian\ Desktop \try extern\a.cpp (5): Error C2065: ' I ': undeclared identifier Error executing cl.exe. A.obj-1 error (s), 0 warning (s) Compilation error. This error is expected because the visibility of the global variables defined in the file extends to the entire program after the link is complete, and in the compile phase,

1 Basic explanation:extern can be placed before a variable or function to mark the definition of a variable or function in another file, prompting the compiler to find its definition in other modules when it encounters this variable and function. Additionally, extern can be used for link designation. Which means that extern has two functions, the first one, when it is used with "C", such as:

One, the use of extern method The following is an explanation of extern in the C language program: In all source files of a source program, an external variable can only be defined once in a file, and other files are accessed through an extern declaration (the source file that defines an external variable can also contain an

Const, static, extern usage summary, constextern Const application: 1. For the basic declaration const int r = 100; // standard const variable declaration and initialization, the compiler will directly replace it with 100 during compilation after the type check. 2. For pointer 1. int x = 10; const int * r = x; // The Pointer Points to a constant. The content pointed to by r cannot be changed through r, but if it is not const, the content can be chang

Transfer from chao_yu,cnblog.com1 Basic explanation : extern can be placed before a variable or function to indicate the definition of a variable or function in another file, prompting the compiler to find its definition in other modules when encountering this variable and function. Also extern can be used for link designation.That is, the extern has two function

Modifiers are used to declare methods that are implemented externally. A common use of the extern modifier is to use the Interop service to dial in a non-Managed code is used with the DllImport property, in which case the method must also be declared as static, as shown in the following example: [DllImport ("Avifil32.dll")]private static extern void Avifileinit ();AttentionThe

Mutual reference between C and C ++ functions extern "C" for an in-depth understanding 1. Introduction C ++ language was originally created as "a better C ", however, this does not mean that the compilation and connection methods used by global variables and functions similar to C in C ++ are the same as those in C. As a language to be compatible with C, C ++ retains the features of some procedural languages (known as "not completely oriented objects

Introduction: extern "C" contains double meanings, which can be obtained literally: first, the target is "extern". Second, the target to be modified is "C. Let's explain these two meanings in detail. Meaning (1) the function or variable restricted by extern is of the extern type: a.