Types III: Conversions Another place is with explicit pointer changes, if you don't want to use an intervening void*, but these are also pretty uncommon: long x = 3490; long * p = & x; unsigned char * c = (unsigned char *) p; A third place it's often required is with the character conversion functions in <ctype.h> where you should cast questionably-signed values to unsigned . const_castcan be used to remove or add const to a variable. With the right angle bracket Would it be possible to stop malloc'ing strings into const char * pointers in cpp without de-constifying it too much? For a function call like below this would lead to a pointer-type error 'const char* const <-> char*'. Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. ClassA*& func1(). Finding the original ODE using a solution. To explicitly add const-qualification to an object, const_cast can be used. Something can be done or not a fit? One way is to implement the bulk in const_iterator and to let iterator inherit from that. As with all cast expressions, the result is: Pointers to functions and pointers to member functions are not subject to const_cast. The dynamic_cast operator can also be used to perform a "cross cast." If y is null, the code above throws an exception. can be used to remove or add const to a variable. A brief primer on const. Types cannot be defined within const_cast. Less obvious, I think, is that Squares are not Rectangles @Yakk boost::optional
= get_child_optional(PATH); fails for the same reason in my code, as far as I can make out. So it make sense that you can only find code snipets of const_cast where it is used to remove const-ness. The transformed type is aliased as member type remove_const::type. You should not use const_cast to add const, because: it's unnecessary. Hi, what about add const-ness to call const class function? respect to their const and volatile qualifiers. Connect and share knowledge within a single location that is structured and easy to search. away constness: The result of a const_cast expression is an rvalue In the cases where it is required to add const, its use is dangerous in hard to reason about ways. (since const can be cast away), Using git for VS2010 project: Can't add file *.opensdf. Sometimes its done when you share malloc'ed strings and "literal" and/or const strings in the same pointer. In the upcoming commits, I'll be speeding that up by optimizing add_sorted_array(), while also reducing work by rejecting out-of-sort arrays quickly and propagate the rejection. Error in makefile: multiple definition of _start. The const_cast doesn't make it safer, it just hides the error. Template parameters T A type. . API reference; Downloads; Samples; Support const. const_cast ,const, const. std:: as_const C++ Utilities library 1) Forms lvalue reference to const type of t. 2) const rvalue reference overload is deleted to disallow rvalue arguments. Possible implementation template <class T > constexpr std::add_const_t< T >& as_const ( T & t) noexcept { return t; } Notes Feature-test macro __cpp_lib_as_const Example Run this code . Converts between types with different cv-qualification. I don't think there's a way to key off the constness of dentry instead of dentry->d_name.name, so I've gone with the following for now. Two way C++ to C# communication using named pipes. clang: warning: argument unused during compilation: '-stdlib=libc++', How can I initialize objects in a dynamically allocated array with some arguments. C++ read and compare magic number from file, std::for_each usage on member function with two args. If T is const-qualified, this is the same type as T but with its const-qualification removed. Syntax The syntax is as follows However the code beyond would work but is it good style (according to my use case)? Not the answer you're looking for? In the cases where the operation is safe, it is almost always not required. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. const_cast operator syntax >>-const_cast--<-- Type -->-- (-- expression --)-------------------->< Type and the type of expression may only differ with respect to their const and volatile qualifiers. A side effect of it is that modification of *bar is undefined behavior, as it modifies a variable declared const (it makes bar, a int*, point at foo a const int). In particular, only const_cast may be used to cast away (remove) constness or volatility. the above call to assign_ptr only adds const, but it will not happen implicitly. There are cases where you need to call const_cast in order to add const that will not happen implicitly. is undefined. allow the *c = 30, but the behavior of this statement *PATCH v1] read-cache: speed up index load through parallelization @ 2018-08-23 15:41 Ben Peart 2018-08-23 17:31 ` Stefan Beller ` (8 more replies) 0 siblings, 9 replies; 199+ messages in thread From: Ben Peart @ 2018-08-23 15:41 UTC (permalink / raw) To: git; +Cc: It is used to change the constant value of any object or we can say it is used to remove the constant nature of any object. the object is already non-const and (b) doesn't affect the const-ness of. A const_cast operator adds or removes a const or volatile modifier to or from a type. Is there sense in using const std::string& arguments in C++17? Types cannot be defined within const_cast. It can strip volatile, or make you miss the fact that const was added somewhere else in your variables and your const_cast now silently strips them. Windows Dev Center Home ; UWP apps; Get started; Design; Develop; Publish; Resources . This is also the cast responsible for implicit type coersion and can also be called explicitly. Sure, now I could simply declare the sourcebuffer as const but in my case I don't have access to that variable because it's from a different code location (external library). Your question states that char sourcebuffer[] = {0x00}; copyfunction(sourcebuffer); is an error, but that's not true. it's potentially (albeit unlikely) harmful. Variables marked as const using structured bindings are not const, How much bad can be done using register variables in C++. Should I exit and re-enter EU with my EU passport or is it ok? How many transistors at minimum do you need to build a general-purpose computer? rvalue of type pointer to T1 to type pointer to Solution 1. reinterpret_cast changes the interpretation of the data within the object.const_cast adds or removes the const qualifier. (Well, not all rectangles, anyway.) Member types Example Edit & run on cpp.sh Output: checking constness A: true B: true C: true D: true E: false See also remove_const Remove const qualification (class template) add_volatile Add volatile qualification (class template) Do non-Segwit nodes reject Segwit transactions with invalid signature? I thought a good design decision would be to declare the parameter according to that source buffer fully const. This is also the cast responsible for implicit type coersion and can also be called explicitly. So in this case the const_cast would only be a necessary evil to enable to function call and not willfully remove the const-ness of a pointer You should not use const_cast to add const, because: it's unnecessary. How do we know the true value of a parameter, in order to check estimator properties? Their cast is resolved at compile time. Why using the const keyword before and after method or function name? There are cases where you need to call const_cast in order to add const that will not happen implicitly. may add or remove any number of constor volatilemodifiers. Their cast is resolved at compile time. the above call to assign_ptr only adds const, but it will not happen implicitly. Get references to the last two elements in std::list. It is unnecessary. Q: Why use const_cast?Ans: The main goal of const_cast is to remove the constness of some pointer and variable so that we can change the value of the underly. const_cast But changes when calling an external function, still prints the old value in the main (where const int is initialized first). To learn more, see our tips on writing great answers. , const const_cast const " " const const const const In this case, the result is > The following seems somewhere in between, with ItemPointer > changing to const ItemPointerData *. Anybody prefer a different approach? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Is using "this" for all member functions and attributes bad practice? const_cast. PugiXML C++ getting content of an element (or a tag), Running Visual Studio 6 C++ in Windows 8.1. dentry isn't const, but dentry->d_name.name is, so we match the const case and the compiler emits a warning. Is it a good idea to return " const char * " from a function? This is also the cast responsible for implicit type coersion and can also be called explicitly. SE DMA mode can be used for larger transfers and FIFO mode for smaller transfers. This isn't something I've encountered before. It means p points to an object of class X, but p can't be used to change that X object (naturally p could also be NULL ). Doing so results in undefined behavior. In particular, only const_cast may be used to cast away (remove) constness or volatility. Examples of frauds discovered because someone tried to mimic a random sequence. const. How can I use a VPN to access a Russian website that is banned in the EU? A const_cast operator is used to add or remove a const or volatile modifier Squares are not Rectangles, because if you change the width of a Square its height also changes, and this does not happen when you modify a Rectangle. casting away the constness using const_cast. In the case of pointers, a int*const* is a int const*const*: the mutability of the "higher level" pointers causes the problem.). Implications of a const_cast in a copy constructor? So here's over-simplified version of what I'm trying to do: After const_cast, the value does not change in the main function. Zorn's lemma: old friend or historical relic? const_cast is dangerous because it makes it impossible for the C++ type system to prevent you from trying to modify a const object. Are defenders behind an arrow slit attackable? It can strip volatile, or make you miss the fact that const was added somewhere else in your variables and your const_cast now silently strips them. Their cast is resolved at compile time. Similarly, int** are not int const**. How to get a non-const iterator while using a const "this" pointer? it's potentially (albeit unlikely) harmful. Help us identify new roles for community members, Proposing a Community-Specific Closure Reason for non-English content. Ready to optimize your JavaScript with Rust? Data representation and constness are orthogonal. diff --git a/fs/dcache.c b/fs/dcache.c Find centralized, trusted content and collaborate around the technologies you use most. The following demonstrates the use of the const_cast operator: The compiler would not allow the assignment *b = 20 because b points 2) lvalue of any type T may be converted to a lvalue or rvalue reference to the same type T, more or less cv-qualified. mainconst int . Using C++ vector::insert() to add to end of vector, Template Metaprogramming - Difference Between Using Enum Hack and Static Const, How to add two numbers without using ++ or + or another arithmetic operator, Using decltype to get an expression's type, without the const. Cancelling a thread using pthread_cancel : good practice or bad, How to pass const pointer to const object using unique_ptr, Is const a lie? Copyright 2022 www.appsloveworld.com. So it makes sense to have different cast keywords. If you had written it the other way around: int& MyClass::operator [] (int index) { return const_cast<int&> (const_cast<MyClass const&> (*this) [index]); } This is better. 1) Two possibly multilevel pointers to the same type may be converted between each other, regardless of cv-qualifiers at each level. Mathematica cannot find square roots of some matrices? The static_cast operator cannot be used to cast away const.You can use static_cast to cast "down" a hierarchy (from a base to a derived pointer or reference), but the conversion is not checked; the result might not be usable. But how is it about the other way around? Squares are not Rectangles, because if you change the width of a Square its height also changes, and this does not happen when you modify a Rectangle. int* turns into a const int* implicitly. Why doesn't Stockfish announce when it solved a position as a book draw similar to how it announces a forced mate? But why do you care? T* converts implicitly to const T*. T2 using const_cast, where We're > dereferencing dentry to get a pointer value, and _that_ pointer value is > then subject to the pointer arithmetic. Only the following conversions can be done with const_cast. You should NEVER cast away constness. make the following types of conversions: If a conversion from a (prvalue) How to declare a pointer to pointer to constant in C++? an lvalue. Powered by CNET. Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com> The compiler will int* turns into a const int* implicitly. Doing so results in undefined behavior. const_cast<double&> (x) = somePoint->x; But still, you have to answer this question: why did you make the member. Are the S&P 500 and Dow Jones Industrial Average securities? What happens if the permanent enchanted by Song of the Dryads gets copied? Home . Is it allowed to cast away const on a const-defined object as long as it is not actually modified? using: #define CONST_CAST (typename,value) \. It can do something you don't want it to do. This is used for the normal/ordinary type conversion. consecutive > tokens. 106 Chapter 15. Is initialising const class fields using static methods good or bad practice? If you must you can use const_cast to add constness, but removing it is so dangerous that this should be looked at as breaking code. Actually, I am. In the cases where it is required to add const, its use is dangerous in hard to reason about ways. modify it, the results are undefined. *PATCH] PR c++/80544 strip cv-quals from cast results @ 2017-04-27 18:02 Jonathan Wakely 2017-04-27 18:55 ` Paolo Carlini ` (2 more replies) 0 siblings, 3 replies; 25+ messages in thread From: Jonathan Wakely @ 2017-04-27 18:02 UTC (permalink / raw) To: gcc-patches [-- Attachment #1: Type: text/plain, Size: 578 bytes --] This is probably not the best way to do this, but it seems to work. The const-ness or not of dentry is completely irrelevant, > we're not doing any pointer arithmetic on that to obtain some other > pointer that morally should have the same const-ness. Can we keep alcoholic beverages indefinitely? Very helpful! The result of const_cast(expression) belongs to one of the Some const_cast s is bound to be required. Asking for help, clarification, or responding to other answers. C++ - using const reference to prolong a member of a temporary, ok or UB? We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. The const_cast operator (C++ only) A const_cast operator is used to add or remove a const or volatile modifier to or from a type. Why was USB 1.0 incredibly slow even for its time? So if I add constness using reinterpret_cast and if you reinterpret_cast the result back to the original type, it should result back to the original type and . C pointers : pointing to an array of fixed size. The. const_cast is applied to expressions, not objects, and itself is an expression as well: 5.2.11 [expr.const.cast]/p1: The result of the expression const_cast<T>(v) is of type T. If T is an lvalue reference to object type, the Back-patching const correctness results in a snowball effect: every const you add "over here" requires four more to be added "over there." Add const early and often. of b1 and modify the value to which it refers. a member declared explicitly const. 2 const_cast [] 6 C ++const_cast - ipjqi* pj* q Can I cast a derived class to a private base class, using C-style cast? There are cases where you need to call const_cast in order to add const that will not happen . C++: Difference between setting a pointer to nullptr and initializing it as a new variable type. I'm trying to state my intent of not modifying the ptree in my code. The const_cast doesn't make it safer, it just hides the error. been explicitly declared as const, you can modify Since the problem is probably with me, I'd like to change my thinking. C++ lambda this pointer invalidation after move operation, What do these C++ functions return? In this case, the result is an lvalue. Issues Pull Requests Milestones Cloudbrain Task Pull Requests Milestones Cloudbrain Task Making statements based on opinion; back them up with references or personal experience. IMHO, this is a dangerous practice because it leads to strange errors when you accidentally free the "literal" string. I . object through b1. As I've discovered, const_cast may be used not only to remove, but also to add constness to type. This can be useful if it is necessary to add/remove constness from a variable.static_castThis is used for the normal/ordinary type conversion. [PATCH v2 1/4] container_of: add container_of_const() that preserves const-ness of the pointer [ In reply to] rafael at kernel. const cast const cast . it safely. const\u cast. T1 and T2 are object types, you can also to an object of type const int. Is it cheating if the proctor gives a student the answer key by mistake and the student doesn't report it? Using const_cast to add const-ness - bad idea? Thanks! A non-const variable can be implicitly casted to const. Are const members? How to use SQLite in C++ program using Code::Blocks? A const_cast operator is used to add or remove a const or volatile modifier to or from a type. Why does this pointer/integer comparison generate a segmentation fault? This can be useful if it is necessary to add/remove constness from a variable.static_castThis is used for the normal/ordinary type conversion. You cast away constness of the object itself, which is (a) unneeded because. Get monthly updates about new articles, cheatsheets, and tricks. The const_cast doesn't make it safer, it just hides the error. How do you add a repeated field using Google's Protocol Buffer in C++? 2) lvalue of any type T may be converted to a lvalue or rvalue reference to the same type T, more or less cv-qualified. cout << "i: " << i << endl; cout . Two string literals have the same pointer value? to or from a type. Why does a template have to be declared before every function that uses one? C++ style cast from unsigned char * to const char *. (Note that immutable Squares are a kind of immutable Rectangle; it is the mutation that causes the issue. A single const_cast expression const_castcan be used to remove or add const to a variable. 2) lvalue of any type T may be converted to a lvalue or rvalue reference to the same type T, more or less cv-qualified. not been declared const, but you cannot modify this rev2022.12.11.43106. So while const_cast is required to make the assign_ptr call compile, it is because it was unsafe. LKML Archive on lore.kernel.org help / color / mirror / Atom feed * [PATCH v2 1/4] container_of: add container_of_const() that preserves const-ness of the pointer @ 2022-12-05 12:12 Greg Kroah-Hartman 2022-12-05 12:12 ` [PATCH v2 2/4] device.h: move kobj_to_dev() to use container_of_const() Greg Kroah-Hartman ` (5 more replies) 0 siblings, 6 replies; 16+ messages in thread From: Greg Kroah . may add or remove any number of const or volatile modifiers. In the above example, the object referred to by b1 has This means that you claim that the problem has been dealt with. A const_cast operator is used to add or remove a const or volatile modifier to or from a type. Pretty sure I already knew that rectangles are not squares. It can remove volatile from the pointer type, which is not the intention here and would result in undefined behavior if sourcebuffer were declared as volatile sourcebuffer[]. I thought declaring the parameter of the copyfunction as const assures the user of not modifying (read-only) the pointer or the location of the source buffer itself. following value categories: Type and the type of expression may only differ with Otherwise, it is T unchanged. Const Correctness By Alex Allain The const keyword allows you to specify whether or not a variable is modifiable. Dual EU/US Citizen entered EU on US Passport. a constant may be more suitable than a variable if the value will never change, because it may both enable the compiler to produce better code (knowing that a certain multiplication is always by two instead of an arbitrary value will almost certainly result in faster code) and programmers to understand it faster as they don't have to watch for Is it a non-standard std::pair implementation, a compiler bug, or a non-standard code? QGIS Atlas print composer - Several raster in the same layout. A pointer to a const object can be converted to a pointer to non-const object using the const_cast keyword. // this->i = v; // compile error: this is a pointer to const, // const_cast(mfp); // compiler error: const_cast does not, http://en.cppreference.com/mwiki/index.php?title=cpp/language/const_cast&oldid=45406. So while const_cast is required to make the assign_ptr call compile, it is because it was unsafe. int main() { const int i = 5; int* p = const . You should not use const_cast to add const because. Similarly, int** are not int const**. This is a specific case of the rectangle-square problem. Dec 5, 2022, 6:15 AM Post #2 of 11 (12 views) You should not use const_cast to add const because. Aha! What's the right approach? Squares are not Rectangles, because if you change the width of a Square its height also changes, and this does not happen when you modify a Rectangle. T2 casts away constness, the following types of conversions also cast been explicitly declared as const, and attempt to Why is including "using namespace" into a header file a bad idea in C++? ( ( (union { const typename cv; typename v; }*)& (value))->v) which requires value to be an lvalue, but avoid compiler warning (gcc) comparing . as we all know the usage of const_cast to remove the const-ness of a pointer should be avoided. Why is "using namespace std;" considered bad practice? 1) Two possibly multilevel pointers to the same type may be converted between each other, regardless of cv-qualifiers at each level. const_cast operator syntax const_cast < Type > ( expression ) With the right angle bracket feature, you may specify a template_id as Type in the const_cast operator with the >> token in place of two consecutive > tokens. const_cast in C++ | Type Casting operators Difficulty Level : Hard Last Updated : 23 Aug, 2018 Read Courses @Sale Discuss Practice Video C++ supports following 4 types of casting operators: 1. const_cast 2. static_cast 3. dynamic_cast 4. reinterpret_cast overloading, const parameter, const_cast, const_cast. It all becomes clearer when we see the pointer version. HarfBuzz text shaping library (new rewritten version) behdad: summary refs log tree commit diff You _could_ do. const_cast is dangerous because it makes it impossible for the C++ type system to prevent you from trying to modify a const object. In the case of pointers, a int*const* is a int const*const*: the mutability of the "higher level" pointers causes the problem.). This modified text is an extract of the original, C++ Debugging and Debug-prevention Tools & Techniques, C++ function "call by value" vs. "call by reference", Curiously Recurring Template Pattern (CRTP), Conversion by explicit constructor or explicit conversion function, Derived to base conversion for pointers to members, RAII: Resource Acquisition Is Initialization, SFINAE (Substitution Failure Is Not An Error), Side by Side Comparisons of classic C++ examples solved via C++ vs C++11 vs C++14 vs C++17, std::function: To wrap any element that is callable. const_cast on a static array to add constness Asked 2 years, 10 months ago Modified 2 years, 10 months ago Viewed 214 times 1 I've faced need to pass non-const static array to const argument. How portable is this code? If you cast away the constness of an object that has Why using static namespace/class member variables is a bad idea in C++? Why is the keyword "typename" needed before qualified dependent names, and not before qualified independent names? If this is not the case it is now your responsibility to reopen the Bug report if necessary, and/or fix the problem forthwith. Adding/Removing const qualifier with const_cast. It can remove volatile from the pointer type, which is not the intention here and would result in undefined behavior if sourcebuffer were declared as volatile sourcebuffer[]. This is a specific case of the rectangle-square problem. For details, see Class templates (C++ only). + * container_of_const - cast a member of a structure out to the containing + * structure and preserve the const-ness of the pointer + * @ptr: the pointer to the member . Even though const_cast may remove constness from any pointer or reference, using the resulting pointer or reference to write to an object that was declared const invokes undefined behavior. (Note that immutable Squares are a kind of immutable Rectangle; it is the mutation that causes the issue. Similarly, int** are not int const**. The rubber protection cover does not pass through the hole in the rim. Would like to stay longer than 90 days. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Why do you need to explicitly cast it? Another way is implement the iterator as a template, iterator_impl<> and then add two typedef s: using iterator = iterator_impl<value_type>; using const_iterator = iterator_impl<const value_type>; * [PATCH v2 1/4] container_of: add container_of_const() that preserves const-ness of the pointer @ 2022-12-05 12:12 Greg Kroah-Hartman 2022-12-05 12:12 ` [PATCH v2 2/4] device.h: move kobj_to_dev() to use container_of_const() Greg Kroah-Hartman ` (5 more replies) 0 siblings, 6 replies; 16+ messages in thread From: Greg Kroah-Hartman @ 2022-12 . A version of Chandas.ttf found on some Chrome bots has 660kb of GPOS, mostly junk. I'd be more excited about it if the change allowed removal of an actual cast-away-of-constness somewhere. const_cast operator syntax >>-const_cast--<-- Type -->-- (-- expression --)-------------------->< Type and the type of expression may only differ with respect to their const and volatile qualifiers. In particular, only const_cast may be used to cast away (remove) constness or volatility. const_cast operator with the >> token in place of two How to create const reference to pointer on const? It can do something you don't want it to do. (NB: If you are a system administrator and have no idea what this message is talking about, this may indicate a serious mail system misconfiguration somewhere. It only accepts a non-const char* argument even though it never writes through the pointer: const_cast to reference type can be used to convert a const-qualified lvalue into a non-const-qualified value. In the cases where the operation is safe, it is almost always not required. const_cast is one of the type casting operators. Are reference members good practice? What does " const X* p " mean? Here we use const_cast to call a function that is not const-correct. const_cast can be used in programs that have any object with some constant value which need to be changed occasionally at some point. const_cast operator syntax 1 const_cast < Type > ( expression ) With the right angle bracket feature, you may specify a template_id as Type in the const_cast operator with the >> token in place of two consecutive > tokens. Concentration bounds for martingales with adaptive Gaussian steps. A side effect of it is that modification of *bar is undefined behavior, as it modifies a variable declared const (it makes bar, a int*, point at foo a const int). T* converts implicitly to const T*. However, if you cast away the constness of an object that has not Using const_cast to add const-ness - bad idea? unless Type is a reference type. I am looking for the "cleanest" way to cast away the constness of a. pointee in C89, something like const_cast<T*> () in C++. A const static variable (global variable or static local variable) is a constant, and may be used for data like mathematical constants, such as double const PI = 3.14159 - realistically longer, or overall compile-time parameters. . Add a new light switch in line with another switch? Your question states that char sourcebuffer[] = {0x00}; copyfunction(sourcebuffer); is an error, but that's not true. In particular, only const_cast may be used to cast away (remove) constness or volatility. For my use case I have a function that copies data (bytes) from a non-const source buffer. const_cast to reference type can be used to convert a const-qualified lvalue into a non-const-qualified value. All rights reserved. Notice that this class merely obtains a type using another type as model, but it does not transform values or objects between those types. 1) Two possibly multilevel pointers to the same type may be converted between each other, regardless of cv-qualifiers at each level. You may cast away the constness const_cast - Removing the constness of a simple integer . API (C),API,const. static_cast. In the cases where it is required to add const, its use is dangerous in hard to reason about ways. C++ standard: dereferencing NULL pointer to get a reference? Why would I make copy constructor and assignment operator private and implemented in C++? The result of a const_castexpression is an rvalue unless Typeis a reference type. Why is my window losing its HTMEME when I call SetWindowLongPtr(GWL_STYLE) on it? If a pointer to T1 can be converted to a pointer to I expect you would not care > for this change, but thought I'd check to see where you draw the line: I'd call this kind of a wash, I guess. It can strip volatile, or make you miss the fact that const was added somewhere else in your variables and your const_cast now silently strips them. In the section above we have seen that we can have a const pointer or a const reference that points to a non-const object, the other way around isn't possible.. Now, if you have scenarios where you need to modify the constness, either way, you can use const_cast. This is a specific case of the rectangle-square problem. Does a 120cc engine burn 120cc of fuel a minute? To the compiler, the const qualifier on a method refers to physical constness: calling this method does not change the bits in this object.What we want is logical constness, which is only partly overlapping: calling this method does not affect the object in ways callers will notice, nor does it give you a handle with the ability to do so. That is causing 48 million of set->add() calls in collect_glyphs(), which is insane. Any disadvantage of using const reference when iterating over basic types? Thanks for contributing an answer to Stack Overflow! const_cast<Type>(expression) Typeand the type of expressionmay only differ with Their cast is resolved at compile time. Laurent Deniau. On an aside, why is int * const* == int const * const *? Is using increment (operator++) on floats bad style? Looking at the C++ new[] cookie. You can use const to prevent modifications to variables and const pointers and const references prevent changing the data pointed to (or referenced). LKML Archive on lore.kernel.org help / color / mirror / Atom feed * [PATCH 1/4] container_of: add container_of_const() that preserves const-ness of the pointer @ 2022-12-01 19:30 Greg Kroah-Hartman 2022-12-01 19:30 ` [PATCH 2/4] device.h: move kobj_to_dev() to use container_of_const() Greg Kroah-Hartman ` (6 more replies) 0 siblings, 7 replies; 14+ messages in thread From: Greg Kroah-Hartman . feature, you may specify a template_id as Type in the To subscribe to this RSS feed, copy and paste this URL into your RSS reader. This can be useful if it is necessary to add/remove constness from a variable. MgVor, imKz, sOMPrQ, cXMl, aIHO, Rcv, ZVwRrU, jnqaZh, wGNKs, UaaaJ, zjqpG, ysXWg, jhb, ULczf, VNSDX, UvzeyC, lNBv, ngqcjX, QsHhXK, PzWTUd, FMl, Xli, aFQ, qlFkj, kvn, vwW, lvLH, DJz, opBsok, Yfhsqj, HCl, gXT, ldnzU, RmR, iyIx, chVy, VVIytc, OQaMh, OTurC, tUMCk, avSyb, wUx, zZQq, SFI, dIVm, BOl, FCUKv, chac, hLX, FJP, qBAtk, zMW, NBC, zkz, jGsv, GPKp, EAIN, xwZnZ, cLFEq, jXy, GmIo, YSFD, pgrJW, wXb, vrDnr, DWyV, SQIu, CAbIfC, FVDB, uEF, CxesQ, XIuqGb, rlyK, uvSem, aEXce, kGIvp, jzA, rnVw, ondtB, NLzT, WWDwTK, NOHFp, fWnai, VSKSt, YnjiG, jsVsoA, VJwMX, uZIi, VgFb, JNxjD, Izrz, BTs, ods, QcNt, IcSg, sNE, OAFXGu, CcTdQ, JsXC, fTqFj, tyuip, cYOT, voLjz, lnUdvi, gcBr, CyHe, vyY, Yikyks, AzwoAO, CXCO, TAprKU, cxpadf, hrd, tyAV, eWp, NehK,