To subscribe to this RSS feed, copy and paste this URL into your RSS reader. ^~~~~~~~~~~~~~~~~~~~~ Connect and share knowledge within a single location that is structured and easy to search. 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). This is flat out wrong. Find centralized, trusted content and collaborate around the technologies you use most. reinterpret_cast conversion - cppreference.com As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). Java Type Casting - W3Schools 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. You can only do this if you use a synchronization primitive to ensure that there is no race condition. A void pointer can be really useful if the programmer is not sure about the data type of data inputted by the end user. . C - Type Casting - tutorialspoint.com What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. this question. In this case, casting the pointer back to an integer is meaningless, because . ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' c - How to cast an integer to void pointer? - Stack Overflow This will only compile if the destination type is long enough. If your standard library (even if it is not C99) happens to provide these types - use them. To learn more, see our tips on writing great answers. converted back to pointer to void, and the result will compare equal (void *)i Error: cast to 'void *' from smaller integer type 'int'. But then you need to cast your arguments inside your thread function which is quite unsafe cf. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? This allows you to reinterpret the void * as an int. You are just making it bigger by tricking the compiler and the ABI. It's always a good practice to put your #define's in brackets to avoid such surprise. this way I convert an int to a void* which is much better than converting a void* to an int. This page has been accessed 1,655,678 times. I agree passing a dynamically allocated pointer is fine (and I think the best way). Can we typecast void into int? - Quora What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? should we also have a diagnostic for the (presumed) user error? Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. But assuming that it is, as long as the caller and the callee agree, you can do that sort of thing. That could create all kinds of trouble. I'm new to coding and am trying to implement a simple program on my own, that prompts the user the number of residents in an apt complex, the prompts the user to enter the names and apt numbers of each resident. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. Why do small African island nations perform better than African continental nations, considering democracy and human development? Casting int to void* : r/C_Programming - reddit The difference between a and &a is the type. Before I update Xcode, my project still can build and run normally with all devices. 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. If you preorder a special airline meal (e.g. "I think what you should do is actually pass the address of the variable to the function" Not necessarily. sound/soc/codecs/tlv320aic32x4.c:1202:18: warning: cast to smaller Fork 63. I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . Whats the grammar of "For those whose stories they are"? This is known as implicit type casting or type promotion, compiler automatically converts smaller data type to larger data type. "-I.." "-Iinclude\openflow" "-I..\include\openflow" "-Iinclude\openvswitch" "-I..\include\openvsw This is an old C callback mechanism so you can't change that. I'm trying to create a void* from an int. Is it possible to create a concave light? Noncompliant Code Example (memset())For historical reasons, certain C Standard functions accept an argument of type int and convert it to either unsigned char or plain char. a cast of which the programmer should be aware of what (s)he is doing. How Intuit democratizes AI development across teams through reusability. Making statements based on opinion; back them up with references or personal experience. cast to void *' from smaller integer type 'int Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. The program can be set in such a way to ask the user to inform the type of data and . "After the incident", I started to be more careful not to trip over things. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Half your pointer will be garbage. 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.. Does Counterspell prevent from any further spells being cast on a given turn? @jackdoe: It's a waste of human life to write code that "you may need in the future". In such a case the programmer can use a void pointer to point to the location of the unknown data type. An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. 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; 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. whether it was an actual problem is a different matter though. Casting type void to uint8_t - Arduino Forum [PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type warning 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; 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. (i.e. 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. vegan) just to try it, does this inconvenience the caterers and staff? If your standard library (even if it is not C99) happens to provide these types - use them. The result is the same as implicit conversion from the enum's underlying type to the destination type. Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). B Programming Language | What is the History and Concept? reinterpret_cast<void *>(42)). No idea how it amassed 27 upvotes?! rev2023.3.3.43278. Since the 'size' argument for your function is the number of bytes each element in the array needs, I think casting the pointerto (char*) is appropriate. 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). On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. And then assign it to the double variable. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. Mutually exclusive execution using std::atomic? @DavidHeffernan I rephrased that sentence a little. itch" "-I..\include\windows" "-Iinclude" "-I..\include" "-I..\datapath-windows\include" "-IC:\PTHREADS-BUILT\include" "-Xclang" "-fcolor-diagnostics" "-pipe" ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Well occasionally send you account related emails. Asking for help, clarification, or responding to other answers. Type Casting Of Pointers in C - Computer Notes SQL Server does not automatically promote . ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. I don't see how anything bad can happen . Identify those arcade games from a 1983 Brazilian music video, Relation between transaction data and transaction id, The difference between the phonemes /p/ and /b/ in Japanese. clang warnings in v1.42 Issue #265 ocornut/imgui GitHub By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Since all pointers on 64-bit Windows are 64 bits, you are growing the data size from 32 bits backto 64 bits. 471,961 Members | 900 Online. Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. I personally upvoted this answer because by it's first line of text it helped me to understand the reason of this strange error message and what am I, poor idiot, doing :D. Not valid on Windows 64 - long is still 32-bit but pointers are 64-bit. privacy statement. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Click to see the query in the CodeQL repository. Keep in mind that thrArg should exist till the myFcn() uses it. It is purely a compile-time directive which instructs the compiler to treat expression as if it had . 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. Thanks for contributing an answer to Stack Overflow! What is the purpose of non-series Shimano components? Re: [PATCH, PR 53001] Re: Patch to split out new warning flag for How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. What you do here is undefined behavior, and undefined behavior of very practical sort. -1, Uggh. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Find centralized, trusted content and collaborate around the technologies you use most. 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. (int) pthread_self() 64int48intuintptr_t (unsigned int) That's not a good idea if the original object (that was cast to void*) was an integer. A nit: in your version, the cast to void * is unnecessary. What is the point of Thrower's Bandolier? This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. static_cast conversion - cppreference.com Replacing broken pins/legs on a DIP IC package, AC Op-amp integrator with DC Gain Control in LTspice. ncdu: What's going on with this second size column? So,solution #3 works just fine. Can Martian regolith be easily melted with microwaves? The value of float variable is= 37.75. Windows has 32 bit long only on 64 bit as well. 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. Now, what happens when I run it with the thread sanitizer? B language was designed to develop . Casting type void to uint8_t - Arduino Forum ../lib/odp-util.c:5601:9: note: expanded from macro 'SCAN_PUT' By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. What is "cast from integer to pointer of different size" warning? This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. 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. Making statements based on opinion; back them up with references or personal experience. XCode 5.1 is change all architecture to 64 bit. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. linux c-pthreads: problem with local variables. C/C++ , Cerror: cast to 'void *' from smaller integer type 'int'. Compile error on Android ARM Issue #163 cisco/ChezScheme My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? that any valid pointer to void can be converted to this type, then 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. @DietrichEpp can you explain what is race condition with using. windows meson: cast to 'HANDLE' (aka 'void *') from smaller integer But gcc always give me a warning, that i cannot cast an int to a void*. 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. Casting type int to const void* - C / C++ By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Use of Void pointers in C programming language Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? ../lib/odp-util.c:5489:33: note: expanded from macro 'SCAN_PUT_ATTR' Are there tables of wastage rates for different fruit and veg? I think the solution 3> should be the correct one. Getting Command /bin/sh failed with exit code 65 Error with Xcode 5.1 . windows meson: cast to smaller integer type 'unsigned long' from 'void *'. You should perform type conversion based on 64bit build system because the type "int" supports only -32768 ~ 32768. Therefore, you need to change it to long long instead of long in windows for 64 bits. Why does setupterm terminate the program? Bulk update symbol size units from mm to map units in rule-based symbology. 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). Functions return bigint only if the parameter expression is a bigint data type. Here, the Java first converts the int type data into the double type. A sane compiler may throw a warning on lines like this but by no way it should throw an error, because this code is NOT wrong, it is just potentially error-prone, but can be perfectly valid. You think by casting it here that you are avoiding the problem! Casting Pointers - IBM So make sure you understand what you are doing! You are correct, but cocos actually only uses that address as a unique id. I assumed that gcc makes a 65536 out of my define, but I was wrong. How to correctly cast a pointer to int in a 64-bit application? Type conversions - cplusplus.com Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. 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. 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). Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. INT31-C. Ensure that integer conversions do not result in lost or Why is there a voltage on my HDMI and coaxial cables? By clicking Sign up for GitHub, you agree to our terms of service and How to correctly cast a pointer to int in a 64-bit application? Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. 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. with ids being an array of ints and touch being a pointer. I cannot reverse my upvote of user384706's answer, but it's wrong. Based on the design of this function, which modification is right. If pointers are 64 bits and ints are 32 bits, an int is too small to hold a pointer value. The problem is not with casting, but with the target type loosing half of the pointer. 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 Yesterday, I updated Xcode to the newest version (5.1 (5B130a)) to compatible with iOS 7.1. @Martin York: No, it doesn't depend on endiannness. The cast back to int * is not, though. @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. *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 . What I am trying to emphasis that conversion from int to pointer and back again can be frough with problems as you move from platform to platform. 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 ) ^~~~~~~~~~~~~~~~~~~~ Using indicator constraint with two variables. Thanks for contributing an answer to Stack Overflow! 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. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. 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. Connect and share knowledge within a single location that is structured and easy to search. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. INT36-C. Converting a pointer to integer or integer to pointer 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). To learn more, see our tips on writing great answers. A missing cast in the new fast > enumeration code. 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 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". C99 defines the types "intptr_t" and "uintptr_t" which do . The following behavior-changing defect reports were applied retroactively to previously published C++ standards. pthread create managing values generated in function (in c), Establishing TCP socket connection between PHP client and C server on Ubuntu. Do new devs get fired if they can't solve a certain bug? And when assigning to a void pointer, all type information is lost. Implicit conversions - cppreference.com How to Cast a void* ponter to a char without a warning? Cerror: cast to 'void *' from smaller integer type 'int' The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. But you seem to suggest by your answer that the user can pass 5 to pthread_create and then perform the above cast to get it back. This is not even remotely "the correct answer". You could use this code, and it would do the same thing as casting ptr to (char*). All float types are to be converted to double. Connect and share knowledge within a single location that is structured and easy to search. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. 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. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. what does it mean to convert int to void* or vice versa? ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ reinterpret_cast is a type of casting operator used in C++. 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. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] A cast is a way of explicitly informing the compiler that you intend to make the conversion and that you are aware that data loss might occur, or the cast may fail at run time. 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". /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. Any help with this is appreciated. 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. As a result of the integer division 3/2 we get the value 1, which is of the int type. However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. How create a simple program using threads in C? I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. I have looked around and can't seem to find any information on how to do this. */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. */ >> -bool >> +enum conversion_safety >> unsafe_conversion_p (tree type, tree expr, bool . For integer casts in specific, using into() signals that . rev2023.3.3.43278. Use #include to define it. Note the difference between the type casting of a variable and type casting of a pointer. Is it possible to create a concave light? Recovering from a blunder I made while emailing a professor. If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. So you know you can cast it back like this. 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. 4. Type Conversions - C in a Nutshell [Book] - O'Reilly Online Learning The subreddit for the C programming language, Press J to jump to the feed. void* -> integer -> void* rather than integer -> void* -> integer. how to cascade 2d int array to 2d void pointer array? Mutually exclusive execution using std::atomic? Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, error: cast from void* to int loses precision, cast to pointer from integer of different size, pthread code. . 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. Clang warnings for an invalid casting? - The FreeBSD Forums On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. What is the point of Thrower's Bandolier? ^~~~~~~~~~~~~~~~~~~~ Why is there a voltage on my HDMI and coaxial cables? Narrowing Casting (manually) - converting a larger type to a . arrays - I get the error: "cast to smaller integer type 'int' from [] 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). The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. 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).