function-prototypes | 易学教程

The 'this' keyword returns the window object within an object's prototype in Javascript?

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问题 I have the following function in a class: MyClass.prototype.myFunction = function(item, args) { console.log(this); } This function is called from an external library that I don't have access to change. When it's called, the console is logging "this" as the window object instead of the actual instanced object. Upon searching stackoverflow I found this quote: this is set according to how the method is called, and not according to how the method is written. So for obj.method(), this will be set

How to receive unnamed structures as function parameters in C?

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问题 Yesterday while going through this question, I found a curious case of passing and receiving unnamed structures as function parameters. For example, if I have a structure like this, int main () { struct { int a; } var; fun(&var); } Now, what should the prototype of fun be? And how can I use that structure as a structure(pointer) in the function fun ? 回答1: For alignment reasons, this prototype should work: void fun(int *x); And of course: void fun(void *x); I don't see an easy way to actually

How can a parameter have type but no name?

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问题 I saw a question that got marked as a dupe, but one part of the question did not get answered by the dupe, and I did not find a suitable dupe to correct it. So here goes. I once saw a declaration like this: int (*function)(int, float); I don't really understand it. It takes two arguments, but they have no name. How does that work? I mean, when declaring a function like this: int f(int x, int y) { return x+y; } How would that even be possible without identifiers? I have noticed that this don't

Prototyping a function - C++

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问题 Lately, some of my CPP tutorials have used function prototypes . I understand you must initialize the function, but what is the overall use of it? Couldn't you use just as well write the entire function before main() instead of defining a prototype? int returnValue(void); int main() { std::cout << returnValue() << std::endl; return 0; } int returnValue(void) { return 10; } 回答1: One important usage case is when you separate your implementation from the declarations. In other words, you declare

Function prototype in header file doesn't match definition, how to catch this?

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问题 (I found this question which is similar but not a duplicate: How to check validity of header file in C programming language ) I have a function implementation, and a non-matching prototype (same name, different types) which is in a header file. The header file is included by a C file that uses the function, but is not included in the file that defines the function. Here is a minimal test case : header.h: void foo(int bar); File1.c: #include "header.h" int main (int argc, char * argv[]) { int

C++ : Meaning of const charconst

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问题 In one of the C++ programs, I saw a function prototype : int Classifier::command(int argc, const char*const* argv) What does const char*const* argv mean? Is it the same as const char* argv[] ? Does const char** argv also mean the same? 回答1: No, it's not the same as const char *argv[] . The const prohibits modifications of the dereferenced value at the particular level of dereferencing: **argv = x; // not allowed because of the first const *argv = y; // not allowed because of the second const

What is const when you declare a “pointer type” formal (function) parameter “like an const array”?

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问题 What is const when you declare a "pointer type" formal (function) parameter "like an const array"? I.e.: If T is a type identifier, then is: void f(const T arr[]); equivalent to: void f(const T * const arr); or void f(const T * arr); or void f(T * const arr); And how can one to decrypt the C/C++ standards to find this equivalents? :-) Are there differences between C and C++ and between the different incarnations of the standards regarding the meaning of the declarations above? (for C - the

How to extract function prototypes from an elf file?

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问题 I have not been successful in finding an answer on this question. Using GDB, I can use the command "call" to get the prototype of a function. Example: (gdb) call fn $1 = {void (int, int)} 0x8048414 <fn> So, GDB is able to figure out, only from the elf-file, that fn() returns void and takes two integers as arguments. However, I need to use some other tool to extract the function prototypes from an elf file. Preferably, I want to use objdump / readelf. Does anyone know if this is possible? If

Problem extending class with javascript object prototype

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I have got this problem... B is a base class, and A is a derived class... Event though A is derived from B, various objects of A points to the same object of B. I know i have assigned an object of B to the prototype of A to make A child of B. But different objects of A, they should have different address space to hold the variables, right? Can you anyone correct this? function B(){ this.obj = {}; } function A(){ } A.prototype = new B(); var a = new A(); var b = new A(); var c = new A(); console.log(a.obj == b.obj); //prints true console.log(a.obj === b.obj); //prints true a.obj.name =

Function prototype in header file doesn't match definition, how to catch this?

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(I found this question which is similar but not a duplicate: How to check validity of header file in C programming language ) I have a function implementation, and a non-matching prototype (same name, different types) which is in a header file. The header file is included by a C file that uses the function, but is not included in the file that defines the function. Here is a minimal test case : header.h: void foo(int bar); File1.c: #include "header.h" int main (int argc, char * argv[]) { int x = 1; foo(x); return 0; } File 2.c: #include <stdio.h> typedef struct { int x; int y; } t_struct; void