addressof

Does the C preprocessor remove instances of “&*”?

空扰寡人 提交于 2019-12-03 14:42:47
问题 I was playing around with gcc and tried the following bit of code: int A = 42; int *B = &A; int *C = &*B; And C == &A , as expected. But when I try: int *B = NULL; int *C = &*B; Turns out C == NULL , and no segfault. So &*B is not actually dereferencing B before taking its address. My guess is that the preprocessor is stripping out instances of &* and *& before they even get to the compiler since they negate each other, but I can't find any documentation to verify whether this is standard C

Does the C preprocessor remove instances of “&*”?

自古美人都是妖i 提交于 2019-12-03 04:31:21
I was playing around with gcc and tried the following bit of code: int A = 42; int *B = &A; int *C = &*B; And C == &A , as expected. But when I try: int *B = NULL; int *C = &*B; Turns out C == NULL , and no segfault. So &*B is not actually dereferencing B before taking its address. My guess is that the preprocessor is stripping out instances of &* and *& before they even get to the compiler since they negate each other, but I can't find any documentation to verify whether this is standard C or compiler-specific. Is the preprocessor stripping out &* and *& , and can I expect this behavior from

Why is Taking the Address of a Function That is Declared Only Working?

痴心易碎 提交于 2019-12-02 20:06:31
问题 I've asked a question here about whether taking the address of a function forces the compilation of said function specifically with regard to Substitution-Failure-Is-Not-An-Error. The most direct answer to this can be found here: Informally, an object is odr-used if its address is taken, or a reference is bound to it, and a function is odr-used if a function call to it is made or its address is taken. If an object or a function is odr-used, its definition must exist somewhere in the program;

Why is Taking the Address of a Function That is Declared Only Working?

半世苍凉 提交于 2019-12-02 09:15:39
I've asked a question here about whether taking the address of a function forces the compilation of said function specifically with regard to Substitution-Failure-Is-Not-An-Error. The most direct answer to this can be found here : Informally, an object is odr-used if its address is taken, or a reference is bound to it, and a function is odr-used if a function call to it is made or its address is taken. If an object or a function is odr-used, its definition must exist somewhere in the program; a violation of that is a link-time error. But all the compilers I've tested show this as perfectly

VB.net to C# Equivalent of “AddressOf”

走远了吗. 提交于 2019-12-01 19:28:02
I am trying to implement this example http://blog.evonet.com.au/post/Gridview-with-highlighted-search-results.aspx but the only problem I am facing is the AddressOf keyword of VB.net which I am unable to convert in C#.net can anybody help me out with this, what alternative I should use to make it work. Thanks. Edit: I found some searches on stackoverflow regarding similar problems but I am unable to understand them. You can just leave it out. Method groups are implicitly convertible to delegates in C#. return ResultStr.Replace(InputTxt, new MatchEvaluator(ReplaceWords)) Or even simpler(I think

Address of dereferenced pointer construct

北城以北 提交于 2019-12-01 02:05:02
问题 In unqlite c library I found following code: pObj = jx9VmReserveMemObj(&(*pVm),&nIdx); where pVm is: typedef struct jx9_vm jx9_vm; jx9_vm *pVm and function called is declared as: jx9_value * jx9VmReserveMemObj(jx9_vm *, sxu32 *); What for construct &(*pVm) is used in call instead of just pVm ? Is &(*pVm) equivalent to pVm ? 回答1: Quoting C11 , chapter §6.5.3.2, Address and indirection operators [...] If the operand is the result of a unary * operator, neither that operator nor the & operator

Can an address be assigned to a variable in C?

旧城冷巷雨未停 提交于 2019-12-01 00:24:51
Is it possible to assign a variable the address you want, in the memory? I tried to do so but I am getting an error as "Lvalue required as left operand of assignment". int main() { int i = 10; &i = 7200; printf("i=%d address=%u", i, &i); } What is wrong with my approach? Is there any way in C in which we can assign an address we want, to a variable? Not directly. You can do this though : int* i = 7200; .. and then use i (ie. *i = 10) but you will most likely get a crash. This is only meaningful when doing low level development - device drivers, etc... with known memory addreses. Assuming you

Can an address be assigned to a variable in C?

六月ゝ 毕业季﹏ 提交于 2019-11-30 18:17:16
问题 Is it possible to assign a variable the address you want, in the memory? I tried to do so but I am getting an error as "Lvalue required as left operand of assignment". int main() { int i = 10; &i = 7200; printf("i=%d address=%u", i, &i); } What is wrong with my approach? Is there any way in C in which we can assign an address we want, to a variable? 回答1: Not directly. You can do this though : int* i = 7200; .. and then use i (ie. *i = 10) but you will most likely get a crash. This is only

When to use addressof(x) instead of &x?

怎甘沉沦 提交于 2019-11-30 12:24:05
问题 How do I decide whether I need addressof(x) instead of &x when taking the address of an object? Seems like the question was confusing, so a clarification is in order: addressof obviously bypasses the overloaded address-of operator. I'm already aware of that. What I want to know is: How do I know if that's what I really want to do? (Especially when inside a template, etc.) Is there some kind of "rule" that helps me figure out when I need addressof instead of & ? After all, they both return the

What's the ampersand for when used after class name like ostream& operator <<(…)?

和自甴很熟 提交于 2019-11-30 11:56:50
问题 I know about all about pointers and the ampersand means "address of" but what's it mean in this situation? Also, when overloading operators, why is it common declare the parameters with const? 回答1: In that case you are returning a reference to an ostream object. Strictly thinking of ampersand as "address of" will not always work for you. Here's some info from C++ FAQ Lite on references. As far as const goes, const correctness is very important in C++ type safety and something you'll want to