B Programming Language | What is the History and Concept? How can this new ban on drag possibly be considered constitutional? Not the answer you're looking for? On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. C - Type Casting - tutorialspoint.com 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. this way you won't get any warning. Therefore, you need to change it to long long instead of long in windows for 64 bits. Thanks for contributing an answer to Stack Overflow! Keep in mind that thrArg should exist till the myFcn() uses it. Can I tell police to wait and call a lawyer when served with a search warrant? Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. There is absolutely not gurantee that sizeof(int) <= sizeof(void*). Mutually exclusive execution using std::atomic? Fork 63. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. This page was last modified on 12 February 2023, at 18:25. Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. 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. vegan) just to try it, does this inconvenience the caterers and staff? Connect and share knowledge within a single location that is structured and easy to search. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? However, you are also casting the result of this operation to (void*). If int is no larger than pointer to void then one way to store the value is by simply copying the bytes: int i . 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;. Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). Pull requests. This is an old C callback mechanism so you can't change that. */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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. This will only compile if the destination type is long enough. In my case, I was using a 32-bit value that needed to be passed to an OpenGL function as a void * representing an offset into a buffer. If any, how can the original function works without errors if we just ignore the warning. Click to see the query in the CodeQL repository. this way I convert an int to a void* which is much better than converting a void* to an int. ../lib/odp-util.c:5489:33: note: expanded from macro 'SCAN_PUT_ATTR' To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. BUT converting a pointer to void* and back again is well supported (everywhere). Converting one datatype into another is known as type casting or, type-conversion. In a 64bit build a pointer is 64bit (contrary to a 32bit build, where it is 32bit), while an int is 32bit, so this assignment stores a 64bit value in a 32bit storage, which may result in a loss of information. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. 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. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. Typically, long or unsigned long is . SCAN_PUT(ATTR, NULL); That could create all kinds of trouble. The correct answer is, if one does not mind losing data precision. In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. The reinterpret_cast makes the int the size of a pointer and the warning will stop. what does it mean to convert int to void* or vice versa? C / C++ Forums on Bytes. The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. The program can be set in such a way to ask the user to inform the type of data and . Does Counterspell prevent from any further spells being cast on a given turn? My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? 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. We have to pass address of the variable to the function because in function definition argument is pointer variable. 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 Do new devs get fired if they can't solve a certain bug? ncdu: What's going on with this second size column? The value of float variable is= 37.75. 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. Disconnect between goals and daily tasksIs it me, or the industry? Functions return bigint only if the parameter expression is a bigint data type. Such pointers can be stored in 32-bit data types (for instance, int, DWORD). error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. Why is there a voltage on my HDMI and coaxial cables? @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. SQL Server does not automatically promote . Or, they are all wrong. @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. To learn more, see our tips on writing great answers. rev2023.3.3.43278. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. I think the solution 3> should be the correct one. I am an entry level C programmer. 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. INT31-C. Ensure that integer conversions do not result in lost or Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. } SCAN_END_SINGLE(ATTR) By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. vegan) just to try it, does this inconvenience the caterers and staff? B language was designed to develop . As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] I agree passing a dynamically allocated pointer is fine (and I think the best way). How do I set, clear, and toggle a single bit? Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. what does it mean to convert int to void* or vice versa? Making statements based on opinion; back them up with references or personal experience. The cast back to int * is not, though. But then you need to cast your arguments inside your thread function which is quite unsafe cf. I cannot reverse my upvote of user384706's answer, but it's wrong. to your account, [87/252] Compiling C object lib/libopenvswitch.a.p/odp-util.c.obj A nit: in your version, the cast to void * is unnecessary. The problem is not with casting, but with the target type loosing half of the pointer. If we want to get the exact value of 7/5 then we need explicit casting from int to float: Example: int x=7, y=5; Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. The only alternative is really to take time and fix all 64-bit code issues, of which there may be some non-trivial issues. How to convert a factor to integer\numeric without loss of information? 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 A missing cast in the new fast > enumeration code. It generally takes place when in an expression more than one data type is present. The proper way is to cast it to another pointer type. 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. The subreddit for the C programming language, Press J to jump to the feed. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Why does Mister Mxyzptlk need to have a weakness in the comics? Find centralized, trusted content and collaborate around the technologies you use most. If the value is ever used as pointer again that will prove to be an extremely bad idea. 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. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? windows meson: cast to 'HANDLE' (aka 'void *') from smaller integer [that could be a TODO - not to delay solving the ICE]. 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. 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. Whats the grammar of "For those whose stories they are"? 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; He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. How do I count the number of sentences in C using ". For the Nozomi from Shinagawa to Osaka, say on a Saturday afternoon, would tickets/seats typically be available - or would you need to book? Wrong. In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. 471,961 Members | 900 Online. Type Casting in C Language with Examples - Dot Net Tutorials How to use Slater Type Orbitals as a basis functions in matrix method correctly? @BlueMoon Thanks a lot! ^~~~~~~~~~~~~~~~~~~~~ My code is all over the place now but I appreciate you all helping me on my journey to mastery! Visit Microsoft Q&A to post new questions. 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. Here, the Java first converts the int type data into the double type. 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. What is "cast from integer to pointer of different size" warning? Already on GitHub? Asking for help, clarification, or responding to other answers. If the original pointer value represents an address of a byte in memory that does not satisfy the alignment requirement of the target type, then the resulting pointer value is unspecified. Yesterday, I updated Xcode to the newest version (5.1 (5B130a)) to compatible with iOS 7.1. lexborisov Modest Public. This solution is in accordance with INT18-C. You think by casting it here that you are avoiding the problem! ), For those who are interested. Use #include to define it. I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. static_cast on the other hand should deny your stripping away the const qualifier. Casting type void to uint8_t - Arduino Forum How create a simple program using threads in C? how to cascade 2d int array to 2d void pointer array? Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. 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. What happens if you typecast as unsigned first? Cerror: cast to 'void *' from smaller integer type 'int' [PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type warning Implementing From will result in the Into implementation but not vice-versa. This allows you to reinterpret the void * as an int. Why is this sentence from The Great Gatsby grammatical? The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. // OK: lvalue denoting the original d object, // UB: the b subobject is not a base class subobject, // 6. array-to-pointer followed by upcast, https://en.cppreference.com/mwiki/index.php?title=cpp/language/static_cast&oldid=147983, when converting a 'pointer to object' to 'pointer to, the conversion from floating-point values, the conversion from bit-fields to rvalue references, the conversion from integral or enumeration values to enumeration, the conversion from integral or enumeration values to, the conversion from a member of base class type to, a standard-layout class object with no data members, a non-standard-layout union object and a non-static data, for base-to-derived pointer conversions and, the conversion to enumeration types with fixed underlying type, a standard-layout class might have a non-pointer-interconvertible, If the underlying type is not fixed, the behavior is undefined if the value of, If the underlying type is fixed, the result is the same as, one is a union object and the other is a non-static data member of that object, or. ", "!"? STR34-C. Are there tables of wastage rates for different fruit and veg? The preprocessor will replace your code by this: This is unlikely what you are trying to do. The difference between the phonemes /p/ and /b/ in Japanese. 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. This is why you got Error 1 C2036, from your post. @Shahbaz you could but I will not suggest to a C newbie to use globals. Sign in As a result of the integer division 3/2 we get the value 1, which is of the int type. Linear regulator thermal information missing in datasheet. Before I update Xcode, my project still can build and run normally with all devices. 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; Compile error on Android ARM Issue #163 cisco/ChezScheme c - type casting integer to void* - Stack Overflow Identify those arcade games from a 1983 Brazilian music video. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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 ^~~~~~~~~~~~~~~~~~~~ itch" "-I..\include\windows" "-Iinclude" "-I..\include" "-I..\datapath-windows\include" "-IC:\PTHREADS-BUILT\include" "-Xclang" "-fcolor-diagnostics" "-pipe" you can just change architecture to support 32 bit compilation by all below in in Build Settings. If you are going to pass the address you typically need to exert some more control over the lifetime of the object. Issues. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); I'm only guessing here, but I think what you are supposed to do is actually pass the address of the variable to the function. How to use Slater Type Orbitals as a basis functions in matrix method correctly? It is easier to understand and write than any other assembly language. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. privacy statement. You can convert the values from one type to another explicitly using the cast operator as follows (type_name) expression Clang warnings for an invalid casting? - The FreeBSD Forums error: cast from pointer to smaller type 'unsigned int' loses ", "? Casting arguments inside the function is a lot safer. A void pointer can be really useful if the programmer is not sure about the data type of data inputted by the end user. 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. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. 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. converted back to pointer to void, and the result will compare equal What video game is Charlie playing in Poker Face S01E07? Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. If you need to keep the returned address, just keep it as void*.