A nit: in your version, the cast to void * is unnecessary. Not the answer you're looking for? From the question I presume the OP does. Can I tell police to wait and call a lawyer when served with a search warrant? BUT converting a pointer to void* and back again is well supported (everywhere). This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. Asking for help, clarification, or responding to other answers. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Or, they are all wrong. ncdu: What's going on with this second size column? SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); 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. I'm trying to create a void* from an int. It modifies >> Wconversion-real.c, Wconversion-real-integer.c and pr35635.c to be more >> specific > > If the patch passes existing tests, I'd be inclined to leave them > tests alone and add new ones that are specific to what this patch > changes. Bulk update symbol size units from mm to map units in rule-based symbology. If this is the data to a thread procedure, then you quite commonly want to pass by value. I assumed that gcc makes a 65536 out of my define, but I was wrong. casting from int to void* and back to int. Thanks for contributing an answer to Stack Overflow! You are right! See also this documentation.. From and Into are generally intended to be lossless, infalliable conversions.as on the other hand can discard data and lead to bugs in some situations, for example casting a u64 to a usize may truncate the value on a 32-bit host. 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! use $(ARCHS_STANDARD_32_BIT) at Architecture instead of $(ARCHS_STANDARD). How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? There's no proper way to cast this to int in general case. I wish that you write those answer first than the explanation. eg. Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. I'm trying to learn pthreads and thing that keeps bugging me is how do i really pass argument to the function. Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. What is the purpose of non-series Shimano components? It generally takes place when in an expression more than one data type is present. Visit Microsoft Q&A to post new questions. You are getting warnings due to casting a void* to a type of a different size. You should perform type conversion based on 64bit build system because the type "int" supports only -32768 ~ 32768. Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul Your first example is risky because you have to be very careful about the object lifetimes. Update: Today, i download the latest version of cocos2d-x (cocos2d-x 2.2.3). *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 . 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. Windows has 32 bit long only on 64 bit as well. 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 Whats the grammar of "For those whose stories they are"? Create an account to follow your favorite communities and start taking part in conversations. return ((void **) returnPtr);} /* Matrix() */. An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. The problem just occur with Xcode 5.1. Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. 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. Basically its a better version of (void *)i. 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 ) byte -> short -> char -> int -> long -> float -> double. How do I check if a string represents a number (float or int)? 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. Instead of using a long cast, you should cast to size_t. 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 } SCAN_END_SINGLE(ATTR) To learn more, see our tips on writing great answers. I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. - the incident has nothing to do with me; can I use this this way? Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. To learn more, see our tips on writing great answers. ^~~~~~~~~~~~~~~~~~~~~ How Intuit democratizes AI development across teams through reusability. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. However the actual code in question contains an explicit c-style cast to int. The int data type is the primary integer data type in SQL Server. If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. If int is no larger than pointer to void then one way to store the value is by simply copying the bytes: int i . For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. 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. 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. This is a fine way to pass integers to new pthreads, if that is what you need. Don't pass your int as a void*, pass a int* to your int, so you can cast the void* to an int* and copy the dereferenced pointer to your int. What is the point of Thrower's Bandolier? The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. lexborisov Modest Public. Not the answer you're looking for? GitHub. Does Counterspell prevent from any further spells being cast on a given turn? Disconnect between goals and daily tasksIs it me, or the industry? It's always a good practice to put your #define's in brackets to avoid such surprise. ", "? Returns a value of type new-type. The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. Connect and share knowledge within a single location that is structured and easy to search. with ids being an array of ints and touch being a pointer. should we also have a diagnostic for the (presumed) user error? Narrowing Casting (manually) - converting a larger type to a . I am an entry level C programmer. For integer casts in specific, using into() signals that . Why did Ukraine abstain from the UNHRC vote on China? 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; 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. Type casting is when you assign a value of one primitive data type to another type. The text was updated successfully, but these errors were encountered: You signed in with another tab or window. To avoid truncating your pointer, cast it to a type of identical size. The main point is: a pointer has a platform dependent size. Why is this sentence from The Great Gatsby grammatical? 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). Getting Command /bin/sh failed with exit code 65 Error with Xcode 5.1 . vegan) just to try it, does this inconvenience the caterers and staff? Thanks for contributing an answer to Stack Overflow! What is the purpose of non-series Shimano components? Java Type Casting. What is the point of Thrower's Bandolier? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. Don't do that. 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. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. 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. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Terrible solution. And in this context, it is very very very common to see programmers lazily type cast the. For the Nozomi from Shinagawa to Osaka, say on a Saturday afternoon, would tickets/seats typically be available - or would you need to book? ^~~~~~~~~~~~~~~~~~~ What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? This is known as implicit type casting or type promotion, compiler automatically converts smaller data type to larger data type. Connect and share knowledge within a single location that is structured and easy to search. this way I convert an int to a void* which is much better than converting a void* to an int. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. */ >> -bool >> +enum conversion_safety >> unsafe_conversion_p (tree type, tree expr, bool . static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). This will only compile if the destination type is long enough. My code is all over the place now but I appreciate you all helping me on my journey to mastery! equal to the original pointer: First you are using a define, which is not a variable. You need to pass an actual pointer. actually no, as int my be a smaller type than a pointer ;-) But, of course with int64_t it works fine. 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). 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. 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; So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. Once you manage to make this cast, then what?! If you preorder a special airline meal (e.g. To learn more, see our tips on writing great answers. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. Since gcc compiles that you are performing arithmetic between void* and an int (1024). C / C++ Forums on Bytes. a cast of which the programmer should be aware of what (s)he is doing. ^~~~~~~~~~~~~~~~~~~~ It was derived from the BCPL, and the name of the b language is possibly from the BCPL contraction. 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. you can just change architecture to support 32 bit compilation by all below in in Build Settings. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? Can Martian regolith be easily melted with microwaves? 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. "clang" "-Ilib\libopenvswitch.a.p" "-Ilib" "-I..\lib" "-I." Replacing broken pins/legs on a DIP IC package, How to handle a hobby that makes income in US. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. Keep in mind that thrArg should exist till the myFcn() uses it. And then assign it to the double variable. How do I set, clear, and toggle a single bit? For example, the main thread could wait for all of the other threads to end before terminating. If the value is ever used as pointer again that will prove to be an extremely bad idea. Half your pointer will be garbage. @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? The compiler issues the "cast from integer to pointer of different size" warning whenever the value of an integer is converted to a pointer, especially when the memory allocated to a pointer is smaller than the memory allocated to an integer data type. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. A cast converts an object or value from one type to another. Here, the Java first converts the int type data into the double type. Can Martian regolith be easily melted with microwaves? privacy statement. 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. This is why you got Error 1 C2036, from your post. Have a question about this project? In the case of Widening Type Casting, the lower data type (having smaller size) is converted into the higher data type (having larger size). My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Converting a void* to an int is non-portable way that may work or may not! On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. Here is my code: I already tried (void*)M_TABLE_SIZE but then I get an error that I cannot use the * operator. The reinterpret_cast makes the int the size of a pointer and the warning will stop. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Setting a buffer of char* with intermediate casting to int*. The only alternative is really to take time and fix all 64-bit code issues, of which there may be some non-trivial issues. You can fix this error by replacing this line of code. Get the address of a callback function to call dynamically in C++, error: call of overloaded function ambiguous, error: cast from to unsigned int loses precision [-fpermissive]. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. (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. 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. "I think what you should do is actually pass the address of the variable to the function" Not necessarily. 1. Notifications. 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. 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. 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 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). How to use Slater Type Orbitals as a basis functions in matrix method correctly? So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. @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. Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. The preprocessor will replace your code by this: This is unlikely what you are trying to do. Replacing broken pins/legs on a DIP IC package, AC Op-amp integrator with DC Gain Control in LTspice. 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. 471,961 Members | 900 Online. vegan) just to try it, does this inconvenience the caterers and staff? If you are going to pass the address you typically need to exert some more control over the lifetime of the object. how to cascade 2d int array to 2d void pointer array? long guarantees a pointer size on Linux on any machine. 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. To be honest, I think, clang is too restrictive here. Put your define inside a bracket: without a problem. Casting an open pointer to other pointer types and casting other pointer types to an open pointer does not result in a compile time error. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? 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;.
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