Using Kolmogorov complexity to measure difficulty of problems? Projects. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. 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. @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. Do new devs get fired if they can't solve a certain bug? When is casting void pointer needed in C? Any expression can be cast to type void (which means that the result of the expression is ignored), but it's not legal to cast an expression of type void to type int not least because the result of such a cast wouldn't make any sense. Based on the design of this function, which modification is right. 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; Already on GitHub? Changing the type of ids would be the cleanest solution, but I decided against it when being confronted with this issue myself, as it only introduced a lot of issues with other code that is relying on ids being an int-array. What you do here is undefined behavior, and undefined behavior of very practical sort. 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. Terrible solution. (i.e. pthread passes the argument as a void*. Even if you are compiling your program for a 32-bit computer, you should fix your code to remove these warnings, to ensure your code is easily portable to 64-bit. The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. (void *)i Error: cast to 'void *' from smaller integer type 'int' PS: UBUNTUCLANG3.5 clang -O0 -std=gnu11 -march=native -lm -lpthread pagerank.c -o pagerank c pthreads 4 10.3k 2 21 2015-06-05 Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. 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! 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. You need to pass an actual pointer. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. A nit: in your version, the cast to void * is unnecessary. 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. 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. What video game is Charlie playing in Poker Face S01E07? An open (void) pointer can hold a pointer of any type. B programing language is a language based on basic combined programming or a BCPL, and it is the precursor of the C programming language. How Intuit democratizes AI development across teams through reusability. Acidity of alcohols and basicity of amines. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); Can Martian regolith be easily melted with microwaves? Implementing From will result in the Into implementation but not vice-versa. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. But assuming that it is, as long as the caller and the callee agree, you can do that sort of thing. Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. ncdu: What's going on with this second size column? ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ What is the purpose of non-series Shimano components? To learn more, see our tips on writing great answers. If you preorder a special airline meal (e.g. For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. 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. If this is the data to a thread procedure, then you quite commonly want to pass by value. But then you need to cast your arguments inside your thread function which is quite unsafe cf. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. 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. If any, how can the original function works without errors if we just ignore the warning. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. You could use this code, and it would do the same thing as casting ptr to (char*). Thanks. 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. Connect and share knowledge within a single location that is structured and easy to search. 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 How do I check if a string represents a number (float or int)? Pd = Pa; Similarly, Pc may be type cast to type int and assigned the value Pa. 1. Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. Before I update Xcode, my project still can build and run normally with all devices. However the actual code in question contains an explicit c-style cast to int. If it's anything like cocos2d-iphone v2.x and just based on this slice of code in a core class I wager it's safe to say that cocos2d-x 2.x also is not compatible with 64 bit code, and you can expect all kinds of issues (not just compile-time but also runtime). Mutually exclusive execution using std::atomic? A pointer converted to an integer of sufficient size and back to the same pointer type is guaranteed to have its original value, otherwise the resulting pointer cannot be dereferenced safely ( the round-trip conversion in the opposite direction is not guaranteed [.]) If the function had the correct signature you would not need to cast it explicitly. Just want to point out that the purpose of threads is, +1 absolutely true, but if you take you time to write struct {}, you can save a lot of troubles in the future when you want to receive/send more data then just an int. 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. As for the stack, I've written a few libraries using pthreds, thus I don't agree that what you describe "is quite often the case". Safe downcast may be done with dynamic_cast. this way I convert an int to a void* which is much better than converting a void* to an int. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. STR34-C. returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size); Remembering to delete the pointer after use so that we don't leak. As a result of the integer division 3/2 we get the value 1, which is of the int type. Is pthread_join a must when using pthread in linux? 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. @DavidHeffernan I rephrased that sentence a little. Difficulties with estimation of epsilon-delta limit proof. reinterpret_cast<void *>(42)). Note:You might receive a runtime exception if the pointer contains a value unsuitable for the context. SCAN_PUT_ATTR(key, ATTR, skey, FUNC); Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. So you know you can cast it back like this. . By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Connect and share knowledge within a single location that is structured and easy to search. That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). AC Op-amp integrator with DC Gain Control in LTspice. Such pointers can be stored in 32-bit data types (for instance, int, DWORD). Why does setupterm terminate the program? I am compiling this program in linux gcc compiler.. The text was updated successfully, but these errors were encountered: 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. How to convert a factor to integer\numeric without loss of information? I agree passing a dynamically allocated pointer is fine (and I think the best way). This will only compile if the destination type is long enough. 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. How create a simple program using threads in C? There's no proper way to cast this to int in general case. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' For example, the main thread could wait for all of the other threads to end before terminating. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. It is commonly called a pointer to T and its type is T*. Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. This is an old C callback mechanism so you can't change that. error: cast from pointer to smaller type 'unsigned int' loses information. No idea how it amassed 27 upvotes?! Star 675. C++ how to get the address stored in a void pointer? I need to cast the int from the first function so that I can use it as an argument for the second function. The most general answer is - in no way. Not the answer you're looking for? Actions. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Making statements based on opinion; back them up with references or personal experience. Put your define inside a bracket: #define M_TABLE_SIZE (64*1024) Now, you can do: static const void* M_OFFSET = (void*) M_TABLE_SIZE; without a problem. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. The following behavior-changing defect reports were applied retroactively to previously published C++ standards. How to use Slater Type Orbitals as a basis functions in matrix method correctly? warning C4311: 'type cast': pointer truncation from 'void *' to 'long' in ECPG test files. If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. The int data type is the primary integer data type in SQL Server. But I don't want to edit code in "EAGLView.mm" because it's a "library file". How can this new ban on drag possibly be considered constitutional? this way you won't get any warning. Instead of using a long cast, you should cast to size_t. This page has been accessed 1,655,678 times. This allows you to reinterpret the void * as an int. I cannot reverse my upvote of user384706's answer, but it's wrong. void* -> integer -> void* rather than integer -> void* -> integer. windows meson: cast to smaller integer type 'unsigned long' from 'void *'. GitHub. Whats the grammar of "For those whose stories they are"? what happens when we typecast normal variable to void* or any pointer variable? Are there tables of wastage rates for different fruit and veg? Making statements based on opinion; back them up with references or personal experience. For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. Therefore it is perfectly valid for the compiler to throw an error for a line like. Connect and share knowledge within a single location that is structured and easy to search. GitHub Skip to content Product Solutions Open Source Pricing Sign in Sign up smadaminov / ovs-dpdk-meson-issues Public Notifications Fork 1 Star 1 Code Issues 66 Pull requests Actions Projects 1 Security Insights New issue Making statements based on opinion; back them up with references or personal experience. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. I am an entry level C programmer. Asking for help, clarification, or responding to other answers. What does it mean to convert int to void* or vice versa? 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. equal to the original pointer: First you are using a define, which is not a variable. Api says this is how i should create thread: So if I want to pass an int what I think I should do is: The second example assumes that a pointer is wide enough to store an int. Yeah, the tutorial is doing it wrong. If you cast an int pointer int, you might get back a different integer. I recall there was a TreeNode(int) early on prior to 1.0 release I can't remember why I removed it, if I should felt it was easy enough to cast to (void*) or if it was because it created type inference conflict at the call site. actually no, as int my be a smaller type than a pointer ;-) But, of course with int64_t it works fine. Using Kolmogorov complexity to measure difficulty of problems? This page was last modified on 12 February 2023, at 18:25. Error while setting app icon and launch image in xcode 5.1. The proper way is to cast it to another pointer type. Identify those arcade games from a 1983 Brazilian music video. I'm unfamiliar with XCode, but the solution should be something like follows: Most of the "solutions" above can lose part of the pointer address when casting to a smaller type. And, most of these will not even work on gcc4. C / C++ Forums on Bytes. The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. Keep in mind that thrArg should exist till the myFcn() uses it. It solved my problem too. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. We have to pass address of the variable to the function because in function definition argument is pointer variable. It is easier to understand and write than any other assembly language. Using indicator constraint with two variables. 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). 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; To learn more, see our tips on writing great answers. The result is the same as implicit conversion from the enum's underlying type to the destination type. This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). Find centralized, trusted content and collaborate around the technologies you use most. An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. Why does Mister Mxyzptlk need to have a weakness in the comics? Is it possible to create a concave light? If your standard library (even if it is not C99) happens to provide these types - use them. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. @Martin York: No, it doesn't depend on endiannness. Using an integer address (like &x) is probably wrong, indeed each modification you will execute on x will affect the pass behaviour. Can I tell police to wait and call a lawyer when served with a search warrant? cast operators [edit] When an expression is used in the context where a value of a different type is expected, conversionmay occur: intn =1L;// expression 1L has type long, int is expectedn =2.1;// expression 2.1 has type double, int is expectedchar*p =malloc(10);// expression malloc(10) has type void*, char* is expected Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? You can convert the values from one type to another explicitly using the cast operator as follows (type_name) expression For integer casts in specific, using into() signals that . ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] Use returnPtr[j] = (void *) ((long)ptr + i); ). As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). Maybe you can try this too. On all of them int is 32bit, not 16bit. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. Thanks for contributing an answer to Stack Overflow! Converts between types using a combination of implicit and user-defined conversions. Create an account to follow your favorite communities and start taking part in conversations. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Note the difference between the type casting of a variable and type casting of a pointer. 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
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