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 Don't do that. So,solution #3 works just fine. itch" "-I..\include\windows" "-Iinclude" "-I..\include" "-I..\datapath-windows\include" "-IC:\PTHREADS-BUILT\include" "-Xclang" "-fcolor-diagnostics" "-pipe" I cannot reverse my upvote of user384706's answer, but it's wrong. How Intuit democratizes AI development across teams through reusability. This page has been accessed 1,655,678 times. Your first example is risky because you have to be very careful about the object lifetimes. void* -> integer -> void* rather than integer -> void* -> integer. Create an account to follow your favorite communities and start taking part in conversations. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. rev2023.3.3.43278. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. For the Nozomi from Shinagawa to Osaka, say on a Saturday afternoon, would tickets/seats typically be available - or would you need to book? The following behavior-changing defect reports were applied retroactively to previously published C++ standards. 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Please note that the error I am receiving is "cast to smaller integer type 'int' from 'string' (aka 'char *')" referencing line of code: while (isalpha (residents [i].name) == 0). This page was last modified on 12 February 2023, at 18:25. 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. XCode 5.1 is change all architecture to 64 bit. Where does this (supposedly) Gibson quote come from? (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. static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). this way you won't get any warning. So reinterpret_cast has casted it to long type and then static_cast safely casts long to int, if you are ready do truncte the data. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini pthread create managing values generated in function (in c), Establishing TCP socket connection between PHP client and C server on Ubuntu. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); Thanks for contributing an answer to Stack Overflow! However the actual code in question contains an explicit c-style cast to int. What is the difference between const int*, const int * const, and int const *? 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). Please help me compile Chez Scheme. 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. I would create a structure and pass that as void* to pthread_create. How to get the error message from the error code returned by GetLastError()? It generally takes place when in an expression more than one data type is present. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? GitHub. *PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type warning @ 2023-01-23 13:28 Hans de Goede 2023-01-23 13:56 ` Hans de Goede 0 siblings, 1 reply; 2+ messages in thread From: Hans de Goede @ 2023-01-23 13:28 UTC (permalink / raw) To: Mark Gross Cc: Hans de Goede, Andy Shevchenko, platform-driver-x86, kernel test robot Fix the following . Type casting is when you assign a value of one primitive data type to another 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. What video game is Charlie playing in Poker Face S01E07? to the original pointer: The following type designates an unsigned integer type with the This is not even remotely "the correct answer". You are just making it bigger by tricking the compiler and the ABI. C / C++ Forums on Bytes. @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. But I don't want to edit code in "EAGLView.mm" because it's a "library file". Have a question about this project? If you cast an int pointer int, you might get back a different integer. If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. However even though their types are different, the address is going to be the same. An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. 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. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. You can use any other pointer, or you can use (size_t), which is 64 bits. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. You may declare a const int variable and cast its reference to the void*. Therefore it is perfectly valid for the compiler to throw an error for a line like. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. How Intuit democratizes AI development across teams through reusability. Why does flowing off the end of a non-void function without returning a value not produce a compiler error? Converts between types using a combination of implicit and user-defined conversions. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? - the incident has nothing to do with me; can I use this this way? If any, how can the original function works without errors if we just ignore the warning. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. Now, what happens when I run it with the thread sanitizer? Fork 63. 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 to correctly cast a pointer to int in a 64-bit application? 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 [.]) Windows has 32 bit long only on 64 bit as well. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. The problem is not with casting, but with the target type loosing half of the pointer. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' Why does setupterm terminate the program? And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. Here, the Java first converts the int type data into the double type. Connect and share knowledge within a single location that is structured and easy to search. Can I tell police to wait and call a lawyer when served with a search warrant? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Asking for help, clarification, or responding to other answers. 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). The most general answer is - in no way. If the sizes are different then endianess comes into play. 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. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. In such a case the programmer can use a void pointer to point to the location of the unknown data type. Bulk update symbol size units from mm to map units in rule-based symbology. You are getting warnings due to casting a void* to a type of a different size. 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. @Shahbaz you could but I will not suggest to a C newbie to use globals. All character types are to be converted to an integer. Disconnect between goals and daily tasksIs it me, or the industry? (int*)Pc = pa; After the execution of the above code all the three pointers, i.e., Pa, Pd, and Pc, point to the value 150. Such pointers can be stored in 32-bit data types (for instance, int, DWORD). It's always a good practice to put your #define's in brackets to avoid such surprise. 10) A prvalue of type pointer to void (possibly cv-qualified) can be converted to pointer to any object type. I am compiling this program in linux gcc compiler.. To cast such pointers to 32-bit types and vice versa special functions are used: void * Handle64ToHandle ( const void * POINTER_64 h ) void * POINTER_64 HandleToHandle64 ( const void *h ) long HandleToLong ( const void *h ) unsigned long HandleToUlong ( const void *h ) 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; Bulk update symbol size units from mm to map units in rule-based symbology. Actions. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. 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 done by the compiler on its own, without any external trigger from the user. 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. I assumed that gcc makes a 65536 out of my define, but I was wrong. static_cast on the other hand should deny your stripping away the const qualifier. Thanks for pointing that out. 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. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. what does it mean to convert int to void* or vice versa? for saving RAM), use union, and make sure, if the mem address is treated as an int only if you know it was last set as an int. What is the point of Thrower's Bandolier? Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ For integer casts in specific, using into() signals that . I have looked around and can't seem to find any information on how to do this. You could use this code, and it would do the same thing as casting ptr to (char*). How do I align things in the following tabular environment? If the value is ever used as pointer again that will prove to be an extremely bad idea. Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. 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. Why does Mister Mxyzptlk need to have a weakness in the comics? Yeah, the tutorial is doing it wrong. 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. Replacing broken pins/legs on a DIP IC package, How to handle a hobby that makes income in US. To learn more, see our tips on writing great answers. There are ways to prevent this: pass a dynamic allocated argument if your not the passing thread is not static or if your argument is a local variable, otherwise there is no issue. C99 defines the types "intptr_t" and "uintptr_t" which do . It was derived from the BCPL, and the name of the b language is possibly from the BCPL contraction. How can this new ban on drag possibly be considered constitutional? Returns a value of type new-type. The difference between the phonemes /p/ and /b/ in Japanese. Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. Narrowing Casting (manually) - converting a larger type to a . If you preorder a special airline meal (e.g. (void *)i Error: cast to 'void *' from smaller integer type 'int'. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. that any valid pointer to void can be converted to this type, then Since gcc compiles that you are performing arithmetic between void* and an int (1024). The subreddit for the C programming language, Press J to jump to the feed. The cast back to int * is not, though. Please note that the error I am receiving is "cast to smaller integer type 'int' from 'string' (aka 'char *')" referencing line of code: while (isalpha(residents[i].name) == 0). Is a PhD visitor considered as a visiting scholar. ^~~~~~~~~~~~~~~~~~~ But I'm nitpicking .. This solution is in accordance with INT18-C. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' rev2023.3.3.43278. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Recovering from a blunder I made while emailing a professor. 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. 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. . property that any valid pointer to void can be converted to this type, } SCAN_END_SINGLE(ATTR) I'm trying to create a void* from an int. 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). To be honest, I think, clang is too restrictive here. 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. return ((void **) returnPtr);} /* Matrix() */. Already on GitHub? Java Type Casting. You can convert the values from one type to another explicitly using the cast operator as follows (type_name) expression This allows you to reinterpret the void * as an int. Using Kolmogorov complexity to measure difficulty of problems? And when assigning to a void pointer, all type information is lost. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. Is pthread_join a must when using pthread in linux? ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. Most answers just try to extract 32 useless bits out of the argument. The problem was there before, you just are being notified of it. SCAN_PUT_ATTR(mask, ATTR, smask, FUNC); BUT converting a pointer to void* and back again is well supported (everywhere). Why is this sentence from The Great Gatsby grammatical? 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! : iPhone Retina 4-inch 64-bit) is selected. 1. reinterpret_cast is a type of casting operator used in C++. I wish that you write those answer first than the explanation. A nit: in your version, the cast to void * is unnecessary. If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. 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). Why is there a voltage on my HDMI and coaxial cables? If you are going to pass the address you typically need to exert some more control over the lifetime of the object. That's not a good idea if the original object (that was cast to void*) was an integer. What is the purpose of non-series Shimano components? this way you won't get any warning. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. How to use Slater Type Orbitals as a basis functions in matrix method correctly? How to notate a grace note at the start of a bar with lilypond? ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ If the original type is a void *, converting to an int may lose date on platforms where sizeof(void *) != sizeof(int) (which is true of LP64 programming model). All float types are to be converted to double. @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. Just edited. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. rev2023.3.3.43278. @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. "-I.." "-Iinclude\openflow" "-I..\include\openflow" "-Iinclude\openvswitch" "-I..\include\openvsw 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. This is what the second warning is telling you. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' lexborisov Modest Public. Don't do that. 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. Why do small African island nations perform better than African continental nations, considering democracy and human development? Maybe you can try this too. I need to cast the int from the first function so that I can use it as an argument for the second function. There is no "correct" way to store a 64-bit pointer in an 32-bit integer. How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. 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. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : // 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. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. The preprocesor absolutely will not perform arithmetic. 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. The calculated expression consists of two operations. @Xax: Here's a fixed version, without the race condition: gist.github.com/depp/241d6f839b799042c409, gist.github.com/depp/3f04508a88a114734195, How Intuit democratizes AI development across teams through reusability. 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. This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). In 64-bit programs, the size of the pointer is 64 bits, and cannot be put into the int type, which remains 32-bit in almost all systems. Why do academics stay as adjuncts for years rather than move around? Making statements based on opinion; back them up with references or personal experience. I'm using cocos2d-x-2.2.2. "After the incident", I started to be more careful not to trip over things. The preprocessor will replace your code by this: This is unlikely what you are trying to do. For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. 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. Wrong. /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. If you preorder a special airline meal (e.g. Use returnPtr[j] = (void *) ((long)ptr + i); ). LLNL's tutorial is bad and they should feel bad. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. 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. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' There is absolutely not gurantee that sizeof(int) <= sizeof(void*). 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]. 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 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. 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;. Then i can continue compiling. vegan) just to try it, does this inconvenience the caterers and staff? Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. And in this context, it is very very very common to see programmers lazily type cast the. 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. rev2023.3.3.43278. for (i=0, j=0; j