Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. The proper way is to cast it to another pointer type. should we also have a diagnostic for the (presumed) user error? "because the type "int" supports only -32768 ~ 32768" This is not true for any modern desktop or mobile OS or any OS that is targeted by cocos2d-x. Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin? reinterpret_cast<void *>(42)). This example is noncompliant on an implementation where pointers are 64 bits and unsigned integers are 32 bits because the result of converting the 64-bit ptr cannot be represented in the 32-bit integer type. You should perform type conversion based on 64bit build system because the type "int" supports only -32768 ~ 32768. Cast unsigned char (uint8 *) pointer to unsigned long (uint32 *) pointer rev2023.3.3.43278. INT36-C. Converting a pointer to integer or integer to pointer For the remaining integral types, the result is the value of the enum if it can be represented by the target type and unspecified otherwise. If pointers are 64 bits and ints are 32 bits, an int is too small to hold a pointer value. The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. For example, the main thread could wait for all of the other threads to end before terminating. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. If the value is ever used as pointer again that will prove to be an extremely bad idea. What video game is Charlie playing in Poker Face S01E07? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? On all of them int is 32bit, not 16bit. cast to 'double *' from smaller integer type 'unsigned int' The C compiler is gcc, clang version 3.9.1, target aarch64--linux-android, thread model posix. casting from int to void* and back to int. Asking for help, clarification, or responding to other answers. If you convert (void*) to (long) no precision is lost, then by assigning the (long) to an (int), it properly truncates the number to fit. Can Martian regolith be easily melted with microwaves? The main point is: a pointer has a platform dependent size. Is it possible to create a concave light? This allows you to reinterpret the void * as an int. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? There is absolutely not gurantee that sizeof(int) <= sizeof(void*). Or, they are all wrong. What happens if you typecast as unsigned first? The compiler issues the "cast from integer to pointer of different size" warning whenever the value of an integer is converted to a pointer, especially when the memory allocated to a pointer is smaller than the memory allocated to an integer data type. 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). It's an int type guaranteed to be big enough to contain a pointer. It is easier to understand and write than any other assembly language. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Why is there a voltage on my HDMI and coaxial cables? Have a question about this project? Connect and share knowledge within a single location that is structured and easy to search. If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. static_cast on the other hand should deny your stripping away the const qualifier. Just re-enforcing the old behavior of Xcode 5.0 and earlier versions, that already cut away parts of the address by casting it to int, won't introduce any new bugs and avoids the need to learn and understand lots of implementation-internal cocos code. You need to pass an actual pointer. B Programming Language | What is the History and Concept? rev2023.3.3.43278. Visit Microsoft Q&A to post new questions. ncdu: What's going on with this second size column? Recovering from a blunder I made while emailing a professor. Find centralized, trusted content and collaborate around the technologies you use most. this question. What you do here is undefined behavior, and undefined behavior of very practical sort. Use of Void pointers in C programming language @DietrichEpp can you explain what is race condition with using. Once you manage to make this cast, then what?! Projects. 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. Thanks for contributing an answer to Stack Overflow! Here, the Java first converts the int type data into the double type. I am compiling this program in linux gcc compiler.. Floating-point conversions ../lib/odp-util.c:5489:33: note: expanded from macro 'SCAN_PUT_ATTR' 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. Bulk update symbol size units from mm to map units in rule-based symbology. Asking for help, clarification, or responding to other answers. windows meson: cast to smaller integer type 'unsigned long' from 'void If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. Remarks. Thanks for contributing an answer to Stack Overflow! So the compiler is very picky here and the correct solution to make the code compile again and still let it show the exact same behavior like in Xcode 5.0 is to first cast to an integer type with a size that matches the one of a pointer and to then do a second cast to the int that we actually want: ids [i] = (int) (size_t)touch; Thanks for contributing an answer to Stack Overflow! If the source type is bool, the value false is converted to zero and the value true is converted to the value one of the destination type (note that if the destination type is int, this is an integer promotion, not an integer conversion). If you need to keep the returned address, just keep it as void*. Click to see the query in the CodeQL repository. And, most of these will not even work on gcc4. Instead of using a long cast, you should cast to size_t. Next, when doing pointer arithmetic, the addition operation will use the pointer's type to determine how many bytes to add to it when incrementing it. A void pointer can be really useful if the programmer is not sure about the data type of data inputted by the end user. If the sizes are different then endianess comes into play. This returns the first 32 bits of the pointer which may be the top or the bottom depending on big versus little endian, as comment #2 said. How to use Slater Type Orbitals as a basis functions in matrix method correctly? rev2023.3.3.43278. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Using an integer address (like &x) is probably wrong, indeed each modification you will execute on x will affect the pass behaviour. Using printf with a pointer to float gives an error, Meaning of int (*) (int *) = 5 (or any integer value), Casting int to void* loses precision, and what is the solution in required cases, Acidity of alcohols and basicity of amines. ../lib/odp-util.c:5601:9: note: expanded from macro 'SCAN_PUT' If you preorder a special airline meal (e.g. If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. Bulk update symbol size units from mm to map units in rule-based symbology. -1, Uggh. You just need to suppress the warning, and this will do it: This may offend your sensibilities, but it's very short and has no race conditions (as you'd have if you used &i). And in the function you get the value of the pointer by using the dereference operator *: Please read why glib provide macros for this kind of conversions, there's no need to repeat the text here. "After the incident", I started to be more careful not to trip over things. In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. And then assign it to the double variable. Clang warnings for an invalid casting? - The FreeBSD Forums Fix for objc/45925 Sign up for a free GitHub account to open an issue and contact its maintainers and the community. SCAN_PUT_ATTR(key, ATTR, skey, FUNC); Error while setting app icon and launch image in xcode 5.1. this way I convert an int to a void* which is much better than converting a void* to an int. And in this context, it is very very very common to see programmers lazily type cast the. 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. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Referring to N1570 7.20.1.4/p1 (Integer types capable of holding object pointers): The following type designates a signed integer type with the property My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Converting one datatype into another is known as type casting or, type-conversion. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? unsigned long call_fn = (unsigned long)FUNC; But gcc always give me a warning, that i cannot cast an int to a void*. Fork 63. (Also, check out how it prints "5" twice), passing a unique pointer to each thread wont race, and you can get/save any kind of information in the th struct. *sound/soc/codecs/tlv320aic32x4.c:1202:18: warning: cast to smaller integer type 'enum aic32x4_type' from 'void *' @ 2022-04-22 9:48 kernel test robot 0 siblings, 0 . You are just making it bigger by tricking the compiler and the ABI. All character types are to be converted to an integer. converted back to pointer to void, and the result will compare equal What is the point of Thrower's Bandolier? cast to 'void *' from smaller integer type 'int' The cast back to int * is not, though. Note:You might receive a runtime exception if the pointer contains a value unsuitable for the context. void* -> integer -> void* rather than integer -> void* -> integer. You need to cast the void* pointer to a char* pointer - and then dereference that char* pointer to give you the char that it points to! This is not even remotely "the correct answer". 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. How do I set, clear, and toggle a single bit? error: cast from 'void*' to 'int' loses precision - Stack Overflow So,solution #3 works just fine. Use returnPtr[j] = (void *) ((long)ptr + i); ). - the incident has nothing to do with me; can I use this this way? In simple example code like this it's very easy to convince yourself that there's no problem, but in more elaborate real-world scenarios it's very easy to make this mistake inadvertently. You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : then converted back to pointer to void, and the result will compare Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. I need to cast the int from the first function so that I can use it as an argument for the second function. Casting an open pointer to other pointer types and casting other pointer types to an open pointer does not result in a compile time error. Java Type Casting. By clicking Sign up for GitHub, you agree to our terms of service and We have to pass address of the variable to the function because in function definition argument is pointer variable. Where does this (supposedly) Gibson quote come from? static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' Hence there is no loss in data. Safe downcast may be done with dynamic_cast. Why did Ukraine abstain from the UNHRC vote on China? To learn more, see our tips on writing great answers. I cannot reverse my upvote of user384706's answer, but it's wrong. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. However, you are also casting the result of this operation to (void*). The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. @BlueMoon Thanks a lot! Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Star 675. That could create all kinds of trouble. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. Find centralized, trusted content and collaborate around the technologies you use most. ^~~~~~~~~~~~~~~~~~~~~ Why is this sentence from The Great Gatsby grammatical? The following behavior-changing defect reports were applied retroactively to previously published C++ standards. From the question I presume the OP does. Don't do that. Asking for help, clarification, or responding to other answers. Implementing From will result in the Into implementation but not vice-versa. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size); I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. int, bigint, smallint, and tinyint (Transact-SQL) - SQL Server */ >> -bool >> +enum conversion_safety >> unsafe_conversion_p (tree type, tree expr, bool . ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. You are right! If your standard library (even if it is not C99) happens to provide these types - use them. pthread create managing values generated in function (in c), Establishing TCP socket connection between PHP client and C server on Ubuntu. So you know you can cast it back like this. Netdev Archive on lore.kernel.org help / color / mirror / Atom feed * [mst-vhost:vhost 5/52] drivers/block/virtio_blk.c:539:21: warning: assignment to 'void *' from . Find centralized, trusted content and collaborate around the technologies you use most. But assuming that it is, as long as the caller and the callee agree, you can do that sort of thing. What is "cast from integer to pointer of different size" warning? On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. Pd = Pa; Similarly, Pc may be type cast to type int and assigned the value Pa. 1. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? And when assigning to a void pointer, all type information is lost. 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. 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