Star 675. See also this documentation.. From and Into are generally intended to be lossless, infalliable conversions.as on the other hand can discard data and lead to bugs in some situations, for example casting a u64 to a usize may truncate the value on a 32-bit host. The problem was there before, you just are being notified of it. And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' I wish that you write those answer first than the explanation. I assumed that gcc makes a 65536 out of my define, but I was wrong. whether it was an actual problem is a different matter though. Thanks for pointing that out. "After the incident", I started to be more careful not to trip over things. */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; To subscribe to this RSS feed, copy and paste this URL into your RSS reader. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Xcode 5 and iOS 7: Architecture and Valid architectures, xcode build error: Semantic issue cast from pointer to smaller type 'int' loses information, Issues in handling touches on subviews(uiviews) in UIScrollView, Architecture linking error after Xcode 5.1 upgrade, iOS 7.1 gives error after updating to Xcode 5.1, Linker error in Xcode 5.1 with cocos2d-x 3 beta 2. Note the difference between the type casting of a variable and type casting of a pointer. It solved my problem too. Since gcc compiles that you are performing arithmetic between void* and an int (1024). If this is the data to a thread procedure, then you quite commonly want to pass by value. Projects. This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. Note that it's not guaranteed that casting an, Generally this kind of type casting does not lead to any concern as long as the addresses are encoded using the same length as the "variable type" (. Then I build my project, I get the error "Cast from pointer to smaller type 'int' loses information" in EAGLView.mm file (line 408) when 64-bit simulators (e.g. Apparently the clang version in Xcode 5.1 and above is more strict about potential 32bit vs. 64 bit incompatibilities in source code than older clang versions have been. I need to convert the argument to an int for later use: The compiler (GCC version 4.2.4) returns the error: You can cast it to an intptr_t type. C99 defines the types "intptr_t" and "uintptr_t" which do . Implementing From will result in the Into implementation but not vice-versa. Thank you all for your feedback. That's not a good idea if the original object (that was cast to void*) was an integer. I need to cast the int from the first function so that I can use it as an argument for the second function. If you need to keep the returned address, just keep it as void*. Update: Today, i download the latest version of cocos2d-x (cocos2d-x 2.2.3). /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. Why does flowing off the end of a non-void function without returning a value not produce a compiler error? You can also convert values from one type to another explicitly using the cast operator (see Chapter 5 ): ( type_name) expression In the following example, the cast operator causes the division of one integer variable by another to be performed as a floating-point operation: int sum = 22, count = 5; double mean = (double)sum / count; If you preorder a special airline meal (e.g. Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size); for (i=0, j=0; j returnPtr[j] = (void *) (ptr + i); // <<< Compile Errors, Error1error C2036: 'void *' : unknown sizec:\temp\testone\lib\utils.c57, 2> returnPtr[j] = (void *) ((long*)ptr + i); // <<< No compile errors, 3> returnPtr[j] = (void *) ((char*)ptr + i); // <<< No compile errors. You use the address-of operator & to do that int x = 10; void *pointer = &x; And in the function you get the value of the pointer by using the dereference operator *: int y = * ( (int *) pointer); Share Improve this answer Follow edited Apr 15, 2013 at 13:58 answered Apr 15, 2013 at 13:53 Some programmer dude 394k 35 393 602 1 While working with Threads in C, I'm facing the warning, "warning: cast to pointer from integer of different size". We have to pass address of the variable to the function because in function definition argument is pointer variable. how to cascade 2d int array to 2d void pointer array? However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. } SCAN_END_SINGLE(ATTR) rev2023.3.3.43278. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. what does it mean to convert int to void* or vice versa? You may declare a const int variable and cast its reference to the void*. On many systems, an 8-bit unsigned int can be stored at any address while an unsigned 32-bit int must be aligned on an address that is a multiple of 4. pthread passes the argument as a void*. How do I set, clear, and toggle a single bit? Do new devs get fired if they can't solve a certain bug? Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. Press question mark to learn the rest of the keyboard shortcuts. As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. A nit: in your version, the cast to void * is unnecessary. Does a summoned creature play immediately after being summoned by a ready action? To learn more, see our tips on writing great answers. Does Counterspell prevent from any further spells being cast on a given turn? Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. should we also have a diagnostic for the (presumed) user error? What is the purpose of non-series Shimano components? long guarantees a pointer size on Linux on any machine. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. But I don't want to edit code in "EAGLView.mm" because it's a "library file". Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, You should be doing int x = *((int *)arg); You are casting from void * to int that is why you get the warning. Such a downcast makes no runtime checks to ensure that the object's runtime type is actually D, and may only be used safely if this precondition is guaranteed by other means, such as when implementing static polymorphism. There's no proper way to cast this to int in general case. I have a two functions, one that returns an int, and one that takes a const void* as an argument. Making statements based on opinion; back them up with references or personal experience. If int is no larger than pointer to void then one way to store the value is by simply copying the bytes: int i . How to convert a factor to integer\numeric without loss of information? If any, how can the original function works without errors if we just ignore the warning. Does melting sea ices rises global sea level? If you are planning to use pthreads and you are planning to pass the pass function to pthread_create, you have to malloc/free the arguments you are planning to use (even if the threaded function just need a single int). tialized" "-Wno-format" "-Wno-incompatible-pointer-types" "-Werror" "-dM" "-U_MSC_VER" "-D_TIMESPEC_DEFINED" "-D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_SECURE_NO_WA How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. In the first example, the variable c1 of the char type is converted to a temporary variable of the int type, because the second operand in the division operation, the constant 2, is of the higher type int. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. So,solution #3 works just fine. Here, the Java first converts the int type data into the double type. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Asking for help, clarification, or responding to other answers. vegan) just to try it, does this inconvenience the caterers and staff? What is the difference between const int*, const int * const, and int const *? The result is the same as implicit conversion from the enum's underlying type to the destination type. Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin? Create an account to follow your favorite communities and start taking part in conversations. Acidity of alcohols and basicity of amines. (i.e. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. Replacing broken pins/legs on a DIP IC package, AC Op-amp integrator with DC Gain Control in LTspice. If you call your thread creation function like this, then the void* arriving inside of myFcn has the value of the int you put into it. There exist two main syntaxes for generic type-casting: functional and c-like: 1 2 3 4 double x = 10.3; int y; y = int (x); // functional notation y = (int) x; // c-like cast notation The functionality of these generic forms of type-casting is enough for most needs with fundamental data types. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Why is this sentence from The Great Gatsby grammatical? @DietrichEpp can you explain what is race condition with using. That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. Find centralized, trusted content and collaborate around the technologies you use most. It is commonly called a pointer to T and its type is T*. This is an old C callback mechanism so you can't change that. But the problem has still happened. Windows has 32 bit long only on 64 bit as well. Get the address of a callback function to call dynamically in C++, error: call of overloaded function ambiguous, error: cast from to unsigned int loses precision [-fpermissive]. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Basically its a better version of (void *)i. Thanks for contributing an answer to Stack Overflow! privacy statement. The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS, AC Op-amp integrator with DC Gain Control in LTspice, Identify those arcade games from a 1983 Brazilian music video. I understood, but that would introduce dynamic memory and ugly lifetime issues (an object allocated by one thread must be freed by some other) - all just to pass an. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. What video game is Charlie playing in Poker Face S01E07? This allows you to reinterpret the void * as an int. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. You are just making it bigger by tricking the compiler and the ABI. reinterpret_cast<void *>(42)). to the original pointer: The following type designates an unsigned integer type with the Connect and share knowledge within a single location that is structured and easy to search. SCAN_PUT(ATTR, NULL); Converting a void* to an int is non-portable way that may work or may not! ", "!"? The preprocesor absolutely will not perform arithmetic. The bigint data type is intended for use when integer values might exceed the range that is supported by the int data type.. bigint fits between smallmoney and int in the data type precedence chart.. You can use any other pointer, or you can use (size_t), which is 64 bits. Casting int to void* loses precision, and what is the solution in required cases, c++: cast from "const variable*" to "uint32" loses precision, Recovering from a blunder I made while emailing a professor, Relation between transaction data and transaction id. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. Most answers just try to extract 32 useless bits out of the argument. ^~~~~~~~~~~~~~~~~~~~~ The OP wanted to convert a pointer value to a int value, instead, most the answers, one way or the other, tried to wrongly convert the content of arg points to to a int value. For the second example you can make sure that sizeof (int) <= sizeof (void *) by using a static_assert -- this way at least you'll get a notice about it. rev2023.3.3.43278. Yeah, the tutorial is doing it wrong. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. Pull requests. This is flat out wrong. The subreddit for the C programming language, Press J to jump to the feed. ", "? @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. Noncompliant Code Example (memset())For historical reasons, certain C Standard functions accept an argument of type int and convert it to either unsigned char or plain char. The pointer doesn't actually point to anything, but it's the result of an earlier cast from an integer to a pointer (e.g. you can pass the int value as void pointer like (void *)&n where n is integer, and in the function accept void pointer as parameter like void foo (void *n); and finally inside the function convert void pointer to int like, int num = * (int *)n;. with ids being an array of ints and touch being a pointer. The program can be set in such a way to ask the user to inform the type of data and . Bulk update symbol size units from mm to map units in rule-based symbology. As with all cast expressions, the result is: Two objects a and b are pointer-interconvertible if: static_cast may also be used to disambiguate function overloads by performing a function-to-pointer conversion to specific type, as in. Mutually exclusive execution using std::atomic? Click to see the query in the CodeQL repository. Before I update Xcode, my project still can build and run normally with all devices. On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Why does Mister Mxyzptlk need to have a weakness in the comics? then converted back to pointer to void, and the result will compare "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini If your standard library (even if it is not C99) happens to provide these types - use them. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). Well occasionally send you account related emails. Just edited. lexborisov Modest Public. All character types are to be converted to an integer. C / C++ Forums on Bytes. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. Such pointers can be stored in 32-bit data types (for instance, int, DWORD). The best way is, if one can, do not do such casting, instead, if the same memory address has to be shared for pointer and int (e.g. The difference between a and &a is the type. A nit: in your version, the cast to void * is unnecessary. All float types are to be converted to double.
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