cast to void *' from smaller integer type 'int

Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. vegan) just to try it, does this inconvenience the caterers and staff? I am an entry level C programmer. equal to the original pointer: First you are using a define, which is not a variable. It is commonly called a pointer to T and its type is T*. This page has been accessed 1,655,678 times. Yeah, the tutorial is doing it wrong. Not the answer you're looking for? What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? casting from int to void* and back to int - C / C++ ncdu: What's going on with this second size column? Mutually exclusive execution using std::atomic? to the original pointer: The following type designates an unsigned integer type with the Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. ../lib/odp-util.c:5489:33: note: expanded from macro 'SCAN_PUT_ATTR' C99 standard library provides intptr_t and uintptr_t typedefs, which are supposed to be used whenever the need to perform such a cast comes about. It solved my problem too. Using indicator constraint with two variables. Re: [PATCH, PR 53001] Re: Patch to split out new warning flag for I have a two functions, one that returns an int, and one that takes a const void* as an argument. LLNL's tutorial is bad and they should feel bad. RNINGS" "-D_CRT_SECURE_NO_DEPRECATE" -MD -MQ lib/libopenvswitch.a.p/odp-util.c.obj -MF "lib\libopenvswitch.a.p\odp-util.c.obj.d" -o lib/libopenvswitch.a.p/od Converting a void* to an int is non-portable way that may work or may not! Find centralized, trusted content and collaborate around the technologies you use most. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. 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 You think by casting it here that you are avoiding the problem! 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. This is an old C callback mechanism so you can't change that. The preprocesor absolutely will not perform arithmetic. Type casting is when you assign a value of one primitive data type to another type. There's no proper way to cast this to int in general case. For integer casts in specific, using into() signals that . What I am saying is that it would be safer to use new(5) rather than 5 and deal with it appropriately at the other end. Replacing broken pins/legs on a DIP IC package, AC Op-amp integrator with DC Gain Control in LTspice. How to use Slater Type Orbitals as a basis functions in matrix method correctly? The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. To learn more, see our tips on writing great answers. What happens if you typecast as unsigned first? I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . Don't pass your int as a void*, pass a int* to your int, so you can cast the void* to an int* and copy the dereferenced pointer to your int. Can I tell police to wait and call a lawyer when served with a search warrant? Already on GitHub? Asking for help, clarification, or responding to other answers. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. what does it mean to convert int to void* or vice versa? Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? C++ how to get the address stored in a void pointer? Hence there is no loss in data. 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. What is the correct method to cast an int to a void*? clang11 report error: cast to smaller integer type #82 - GitHub what does it mean to convert int to void* or vice versa? Linear regulator thermal information missing in datasheet. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. XCode 5.1 is change all architecture to 64 bit. SCAN_PUT(ATTR, NULL); No idea how it amassed 27 upvotes?! Or, they are all wrong. should we also have a diagnostic for the (presumed) user error? That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. The reinterpret_cast makes the int the size of a pointer and the warning will stop. : iPhone Retina 4-inch 64-bit) is selected. An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. reinterpret_cast<void *>(42)). I think the solution 3> should be the correct one. In the best case this will give the same results as the original code, with no advantages, but in the worst case it will fail in multiple catastrophic ways (type punning, endianness, less efficient, etc. [Solved] Error "Cast from pointer to smaller type 'int' | 9to5Answer To avoid truncating your pointer, cast it to a type of identical size. Not the answer you're looking for? Getting Command /bin/sh failed with exit code 65 Error with Xcode 5.1 . cast to 'void *' from smaller integer type 'int' [] ExplanatioUnlike static_cast, but like const_cast, the reinterpret_cast expression does not compile to any CPU instructions (except when converting between integers and pointers or on obscure architectures where pointer representation depends on its type). Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. However even though their types are different, the address is going to be the same. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); 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. then converted back to pointer to void, and the result will compare Narrowing Casting (manually) - converting a larger type to a . B Programming Language | What is the History and Concept? Projects. If the function had the correct signature you would not need to cast it explicitly. Connect and share knowledge within a single location that is structured and easy to search. c - How to cast an integer to void pointer? - Stack Overflow pthread passes the argument as a void*. LLNL's tutorial is bad and they should feel bad. This explicit cast clearly tells the compiler "Shut up, I know that this code does not look correct, but I do know what I am doing". Taking the above declarations of A, D, ch of the . Implicit Type Conversion is also known as 'automatic type conversion'. To learn more, see our tips on writing great answers. From what I read about casting in the C11 standard, my feeling is, that it is arguable to emit a warning on an explicit conversion. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. Pd = Pa; Similarly, Pc may be type cast to type int and assigned the value Pa. 1. It is purely a compile-time directive which instructs the compiler to treat expression as if it had . If this is the data to a thread procedure, then you quite commonly want to pass by value. windows meson: cast to smaller integer type 'unsigned long' from 'void *'. How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? 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. Making statements based on opinion; back them up with references or personal experience. An open (void) pointer can hold a pointer of any type. Is a PhD visitor considered as a visiting scholar. All float types are to be converted to double. Thanks for pointing that out. If you cast an int pointer int, you might get back a different integer. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini actually no, as int my be a smaller type than a pointer ;-) But, of course with int64_t it works fine. Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. Here, the Java first converts the int type data into the double type. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' 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;. 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). 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: I am using size_t here, because it is always having the same size as a pointer, no matter the platform. static_cast conversion - cppreference.com Casting Pointers - IBM } SCAN_END_SINGLE(ATTR) Acidity of alcohols and basicity of amines. Does Counterspell prevent from any further spells being cast on a given turn? (i.e. What is the difference between const int*, const int * const, and int const *? On all of them int is 32bit, not 16bit. C99 defines the types "intptr_t" and "uintptr_t" which do . 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! If pointers are 64 bits and ints are 32 bits, an int is too small to hold a pointer value. For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. How to use Slater Type Orbitals as a basis functions in matrix method correctly? 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). 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. My code is all over the place now but I appreciate you all helping me on my journey to mastery! How to correctly type cast (void*)? - social.msdn.microsoft.com Replacing broken pins/legs on a DIP IC package, How to handle a hobby that makes income in US. Find centralized, trusted content and collaborate around the technologies you use most. Actions. 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. Well occasionally send you account related emails. 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 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" (. 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 Properly casting a `void*` to an integer in C++ 24,193 Solution 1 I think using intptr_t is the correct intermediate here, since it's guaranteed to be large enough to contain the integral value of the void*, and once I have an integer value I can then truncate it without causing the compiler to complain. Pull requests. Is it possible to create a concave light? The code ((void*)ptr + 1) does not work, because the compiler has no idea what size "void" is, and therefore doesn't know how many bytes to add. This is not a conversion at all. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. What is the point of Thrower's Bandolier? If the object expression refers or points to is actually a base class subobject of an object of type D, the result refers to the enclosing object of type D. Otherwise, the behavior is undefined: When the target type is bool (possibly cv-qualified), the result is false if the original value is zero and true for all other values. You should perform type conversion based on 64bit build system because the type "int" supports only -32768 ~ 32768. -1, Uggh. But the problem has still happened. SQL Server does not automatically promote . 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. ^~~~~~~~~~~~~~~~~~~~ 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. The difference between a and &a is the type. Type Casting in C Language with Examples - Dot Net Tutorials ), For those who are interested. All character types are to be converted to an integer. To learn more, see our tips on writing great answers. Where does this (supposedly) Gibson quote come from? No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. Floating-point conversions As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. 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. Then i can continue compiling. Why did Ukraine abstain from the UNHRC vote on China? You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : Identify those arcade games from a 1983 Brazilian music video. returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size); Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. This forum has migrated to Microsoft Q&A. Not the answer you're looking for? 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. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] 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. Asking for help, clarification, or responding to other answers. A nit: in your version, the cast to void * is unnecessary. 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. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. Any help with this is appreciated. And then assign it to the double variable. Why is this sentence from The Great Gatsby grammatical? rev2023.3.3.43278. Can Martian regolith be easily melted with microwaves? There is absolutely not gurantee that sizeof(int) <= sizeof(void*). Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. 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.. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Therefore, you need to change it to long long instead of long in windows for 64 bits. a is of type int[4], which can be implicitly cast to int* (ie, a pointer to an int) &a is of type int(*)[4] (ie: a pointer to an array of 4 ints). Is it suspicious or odd to stand by the gate of a GA airport watching the planes? 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]. What does casting to void* does when passing arguments to variadic functions? And when assigning to a void pointer, all type information is lost. This is a fine way to pass integers to new pthreads, if that is what you need. that any valid pointer to void can be converted to this type, then Returns a value of type new-type. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. 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. This answer is incorrect for the reasons that have already been mentioned in the comment of, Error "Cast from pointer to smaller type 'int' loses information" in EAGLView.mm when update Xcode to 5.1 (5B130a), http://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models, http://stackoverflow.com/questions/18913906/xcode-5-and-ios-7-architecture-and-valid-architectures, How Intuit democratizes AI development across teams through reusability. p-util.c.obj "-c" ../lib/odp-util.c Connect and share knowledge within a single location that is structured and easy to search. I'm trying to learn pthreads and thing that keeps bugging me is how do i really pass argument to the function. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Instead of using a long cast, you should cast to size_t. clang warnings in v1.42 Issue #265 ocornut/imgui GitHub 10) A prvalue of type pointer to void (possibly cv-qualified) can be converted to pointer to any object type. Find centralized, trusted content and collaborate around the technologies you use most. Java Type Casting - W3Schools ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. So make sure you understand what you are doing! By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' "I think what you should do is actually pass the address of the variable to the function" Not necessarily. If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. How do I align things in the following tabular environment? even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. Here is some piece of code where that error occur: /cocos2d-x-2.2.2/cocos2dx/platform/ios/EAGLView.mm:408:18: Cast from pointer to smaller type 'int' loses information. It generally takes place when in an expression more than one data type is present. A cast specifies a conversion from one type to another. Before I update Xcode, my project still can build and run normally with all devices. Wrong. I have the following function and when I compile it under VS.NET 2005, the following compile warnings show up: Warning1warning C4311: 'type cast' : pointer truncation from 'void *' to 'long'c:\temp\testone\lib\utils.c56Warning2warning C4312: 'type cast' : conversion from 'unsigned long' to 'void *' of greater sizec:\temp\testone\lib\utils.c56, Code Snippet