When is casting void pointer needed in C? Why do small African island nations perform better than African continental nations, considering democracy and human development? Using indicator constraint with two variables. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. casting from int to void* and back to int. 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; It is commonly called a pointer to T and its type is T*. C99 defines the types "intptr_t" and "uintptr_t" which do . Already on GitHub? returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size); As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). 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;. Any help with this is appreciated. Do new devs get fired if they can't solve a certain bug? GitHub. I am compiling this program in linux gcc compiler.. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. Identify those arcade games from a 1983 Brazilian music video. */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. sound/soc/codecs/tlv320aic32x4.c:1202:18: warning: cast to smaller But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. How to Cast a void* ponter to a char without a warning? reinterpret_cast conversion - cppreference.com 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. XCode 5.1 is change all architecture to 64 bit. There's no proper way to cast this to int in general case. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); ^~~~~~~~~~~~~~~~~~~ [] 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). 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. what happens when we typecast normal variable to void* or any pointer variable? 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. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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 [.]) Acidity of alcohols and basicity of amines. 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 // 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. Since all pointers on 64-bit Windows are 64 bits, you are growing the data size from 32 bits backto 64 bits. This is flat out wrong. If the function had the correct signature you would not need to cast it explicitly. Cast characters to unsigned char before converting to larger integer sizes Created by Robert Seacord, last modified by Jill Britton on Oct 03, 2022 Signed character data must be converted to unsigned char before being assigned or converted to a larger signed type. How Intuit democratizes AI development across teams through reusability. @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. . Yeah, the tutorial is doing it wrong. 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. How to use Slater Type Orbitals as a basis functions in matrix method correctly? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. I cannot reverse my upvote of user384706's answer, but it's wrong. @Shahbaz you could but I will not suggest to a C newbie to use globals. Pull requests. Converting one datatype into another is known as type casting or, type-conversion. Where does this (supposedly) Gibson quote come from? Taking the above declarations of A, D, ch of the . The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. 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. Why is this sentence from The Great Gatsby grammatical? Remembering to delete the pointer after use so that we don't leak. Difficulties with estimation of epsilon-delta limit proof. Find centralized, trusted content and collaborate around the technologies you use most. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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:5658:9: note: expanded from macro 'SCAN_END_SINGLE' I wish that you write those answer first than the explanation. pthread passes the argument as a void*. To learn more, see our tips on writing great answers. I am an entry level C programmer. Are there tables of wastage rates for different fruit and veg? 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. And when assigning to a void pointer, all type information is lost. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' 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. static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). What is the difference between const int*, const int * const, and int const *? and how to print the thread id of 2d array argument? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Whats the grammar of "For those whose stories they are"? I'm using cocos2d-x-2.2.2. What is the point of Thrower's Bandolier? All character types are to be converted to an integer. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Java Type Casting (With Examples) - Programiz 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. Casting int to void* : r/C_Programming - reddit 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;. Is it possible to create a concave light? Not the answer you're looking for? c - Cast int to void* - Stack Overflow The value of float variable is= 37.75. Cast unsigned char (uint8 *) pointer to unsigned long (uint32 *) pointer In simple example code like this it's very easy to convince yourself that there's no problem, but in more elaborate real-world scenarios it's very easy to make this mistake inadvertently. 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; 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". Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. How to correctly cast a pointer to int in a 64-bit application? 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; windows meson: cast to 'HANDLE' (aka 'void *') from smaller integer This is known as implicit type casting or type promotion, compiler automatically converts smaller data type to larger data type. And, most of these will not even work on gcc4. I assumed that gcc makes a 65536 out of my define, but I was wrong. The following program casts a double to an int. Connect and share knowledge within a single location that is structured and easy to search. 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. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini It is done by the compiler on its own, without any external trigger from the user. Cast Operations - Oracle } SCAN_END_SINGLE(ATTR) Can I tell police to wait and call a lawyer when served with a search warrant? A nit: in your version, the cast to void * is unnecessary. linux c-pthreads: problem with local variables. Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. Or, they are all wrong. How do I force make/GCC to show me the commands? Thanks. You can fix this error by replacing this line of code. A cast converts an object or value from one type to another. 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). 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). Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" If the value is ever used as pointer again that will prove to be an extremely bad idea. To learn more, see our tips on writing great answers. On many systems, an 8-bit unsigned int can be stored at any address while an unsigned 32-bit int must be aligned on an address that is a multiple of 4. For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? 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. eg. In the case of Widening Type Casting, the lower data type (having smaller size) is converted into the higher data type (having larger size). I have a two functions, one that returns an int, and one that takes a const void* as an argument. For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. This allows you to reinterpret the void * as an int. Returns a value of type new-type. Windows has 32 bit long only on 64 bit as well. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Wrong. The main point is: a pointer has a platform dependent size. Why does Mister Mxyzptlk need to have a weakness in the comics? A missing cast in the new fast > enumeration code. Why does setupterm terminate the program? should we also have a diagnostic for the (presumed) user error? p-util.c.obj "-c" ../lib/odp-util.c The problem was there before, you just are being notified of it. 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. int, bigint, smallint, and tinyint (Transact-SQL) - SQL Server By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Before I update Xcode, my project still can build and run normally with all devices. long guarantees a pointer size on Linux on any machine. Evaluate integer expressions in a larger size before comparing or assigning to that size.Note that (time_+t)-1 also complies with INT31-C-EX3. ^~~~~~~~~~~~~~~~~~~~ ^~~~~~~~~~~~~~~~~~~~~ LLNL's tutorial is bad and they should feel bad. Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. to the original pointer: The following type designates an unsigned integer type with the 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. "-I.." "-Iinclude\openflow" "-I..\include\openflow" "-Iinclude\openvswitch" "-I..\include\openvsw Find centralized, trusted content and collaborate around the technologies you use most. But I'm nitpicking .. Why is there a voltage on my HDMI and coaxial cables? 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. ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' equal to the original pointer: First you are using a define, which is not a variable. Using Kolmogorov complexity to measure difficulty of problems? 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. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? c - type casting integer to void* - Stack Overflow (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. x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. The difference between the phonemes /p/ and /b/ in Japanese. "After the incident", I started to be more careful not to trip over things. How to use Slater Type Orbitals as a basis functions in matrix method correctly? For integer casts in specific, using into() signals that . If you cast an int pointer int, you might get back a different integer. 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. Pd = Pa; Similarly, Pc may be type cast to type int and assigned the value Pa. 1. What is the point of Thrower's Bandolier? This is what the second warning is telling you. } SCAN_END_SINGLE(ATTR) Not the answer you're looking for? There's probably little you can do except look or hope for a fixed 2.x version or upgrade to 3.x (I would assume it's 64-bit safe but this is just a guess, do research this issue before you upgrade). Since gcc compiles that you are performing arithmetic between void* and an int (1024). To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. Making statements based on opinion; back them up with references or personal experience. converted back to pointer to void, and the result will compare equal From that point on, you are dealing with 32 bits. 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 ) INT31-C. Ensure that integer conversions do not result in lost or Yesterday, I updated Xcode to the newest version (5.1 (5B130a)) to compatible with iOS 7.1. Is it possible to create a concave light? rev2023.3.3.43278. Don't do that. @BlueMoon Thanks a lot! Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. 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 Connect and share knowledge within a single location that is structured and easy to search. Yeah, the tutorial is doing it wrong. Casting type int to const void* - C / C++ 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. Bulk update symbol size units from mm to map units in rule-based symbology. All float types are to be converted to double. 1. Star 675. The mapping in pointer<->integer casts is implementation defined, but the intent was that if the pointer type is large enough and isn't forcefully aligned (, But that's different. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Next, when doing pointer arithmetic, the addition operation will use the pointer's type to determine how many bytes to add to it when incrementing it. Java Type Casting - W3Schools @DietrichEpp can you explain what is race condition with using. Narrowing Casting (manually) - converting a larger type to a . I need to cast the int from the first function so that I can use it as an argument for the second function. C / C++ Forums on Bytes. However the actual code in question contains an explicit c-style cast to int. From what I read about casting in the C11 standard, my feeling is, that it is arguable to emit a warning on an explicit conversion. Compile error on Android ARM Issue #163 cisco/ChezScheme Type Casting in C Language with Examples - Dot Net Tutorials