What does it mean to convert int to void* or vice versa? The code ((void*)ptr + 1) does not work, because the compiler has no idea what size "void" is, and therefore doesn't know how many bytes to add. If the destination type is bool, this is a boolean conversion (see below). C++ Tutorial => Conversion between pointer and integer How do I align things in the following tabular environment? 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 If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. 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. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. what does it mean to convert int to void* or vice versa? Pull requests. Asking for help, clarification, or responding to other answers. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. 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. Use of Void pointers in C programming language Why does Mister Mxyzptlk need to have a weakness in the comics? Instead of using a long cast, you should cast to size_t. Issues. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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 For integer casts in specific, using into() signals that . The following behavior-changing defect reports were applied retroactively to previously published C++ standards. with ids being an array of ints and touch being a pointer. If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. You can fix this error by replacing this line of code. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Why do small African island nations perform better than African continental nations, considering democracy and human development? whether it was an actual problem is a different matter though. Converting one datatype into another is known as type casting or, type-conversion. Find centralized, trusted content and collaborate around the technologies you use most. This page has been accessed 1,655,678 times. If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. Typically, long or unsigned long is . 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. 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 ) STR34-C. Cast characters to unsigned char before converting to larger 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. reinterpret_cast is a type of casting operator used in C++. 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. 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. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? FAILED: lib/libopenvswitch.a.p/odp-util.c.obj How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. It's an int type guaranteed to be big enough to contain a pointer. 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; So you know you can cast it back like this. pthread passes the argument as a void*. And, most of these will not even work on gcc4. There is no "correct" way to store a 64-bit pointer in an 32-bit integer. However, you are also casting the result of this operation to (void*). However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. Half your pointer will be garbage. To access the object value, use the * dereference operator: int * p; assert (p == null ); p = new int (5); assert (p != null ); assert (*p == 5); (*p)++; assert (*p == 6); If a pointer contains a null value, it is not pointing to a valid object. 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. Whats the grammar of "For those whose stories they are"? Why is there a voltage on my HDMI and coaxial cables? We have to pass address of the variable to the function because in function definition argument is pointer variable. 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). Thanks for contributing an answer to Stack Overflow! There exist two main syntaxes for generic type-casting: functional and c-like: 1 2 3 4 double x = 10.3; int y; y = int (x); // functional notation y = (int) x; // c-like cast notation The functionality of these generic forms of type-casting is enough for most needs with fundamental data types. Connect and share knowledge within a single location that is structured and easy to search. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Acidity of alcohols and basicity of amines. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? SQL Server does not automatically promote . eg. Making statements based on opinion; back them up with references or personal experience. Why does flowing off the end of a non-void function without returning a value not produce a compiler error? C/C++ , Cerror: cast to 'void *' from smaller integer type 'int'. (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. This example is noncompliant on an implementation where pointers are 64 bits and unsigned integers are 32 bits because the result of converting the 64-bit ptr cannot be represented in the 32-bit integer type. Keep in mind that thrArg should exist till the myFcn() uses it. I'm using cocos2d-x-2.2.2. error: cast from 'void*' to 'int' loses precision - Stack Overflow Casting int to void* : r/C_Programming - reddit If the sizes are different then endianess comes into play. Connect and share knowledge within a single location that is structured and easy to search. 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. And when assigning to a void pointer, all type information is lost. static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. If you cast an int pointer int, you might get back a different integer. 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 What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. What is "cast from integer to pointer of different size" warning? 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 Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. There's no proper way to cast this to int in general case. @Martin York: No, it doesn't depend on endiannness. byte -> short -> char -> int -> long -> float -> double. Is a PhD visitor considered as a visiting scholar. 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; 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.. What is the point of Thrower's Bandolier? linux c-pthreads: problem with local variables. Is it possible to create a concave light? Does Counterspell prevent from any further spells being cast on a given turn? */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; You need to pass an actual pointer. How do I force make/GCC to show me the commands? Why does setupterm terminate the program? How can this new ban on drag possibly be considered constitutional? So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. 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). What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? You are correct, but cocos actually only uses that address as a unique id. Use #include to define it. Thanks for contributing an answer to Stack Overflow! cast to void *' from smaller integer type 'int This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. Based on the design of this function, which modification is right. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? Re: [PATCH, PR 53001] Re: Patch to split out new warning flag for reinterpret_cast conversion - cppreference.com To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. It generally takes place when in an expression more than one data type is present. return ((void **) returnPtr);} /* Matrix() */. 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. 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. 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. 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. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. Thanks for contributing an answer to Stack Overflow! By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Not the answer you're looking for? 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. returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size); 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). I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. This forum has migrated to Microsoft Q&A. From the question I presume the OP does. To learn more, see our tips on writing great answers. Visit Microsoft Q&A to post new questions. In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. Create an account to follow your favorite communities and start taking part in conversations. Compile error on Android ARM Issue #163 cisco/ChezScheme Identify those arcade games from a 1983 Brazilian music video. Where does this (supposedly) Gibson quote come from? that any valid pointer to void can be converted to this type, then Using Kolmogorov complexity to measure difficulty of problems? What you do here is undefined behavior, and undefined behavior of very practical sort. How to notate a grace note at the start of a bar with lilypond? vegan) just to try it, does this inconvenience the caterers and staff? Since all pointers on 64-bit Windows are 64 bits, you are growing the data size from 32 bits backto 64 bits. 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. If your standard library (even if it is not C99) happens to provide these types - use them. Find centralized, trusted content and collaborate around the technologies you use most. If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. error: cast from pointer to smaller type 'unsigned int' loses If your standard library (even if it is not C99) happens to provide these types - use them. reinterpret_cast<void *>(42)). Such a downcast makes no runtime checks to ensure that the object's runtime type is actually D, and may only be used safely if this precondition is guaranteed by other means, such as when implementing static polymorphism. The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. warning C4311: 'type cast': pointer truncation from 'void *' to 'long' in ECPG test files. rev2023.3.3.43278. The preprocesor absolutely will not perform arithmetic. Before I update Xcode, my project still can build and run normally with all devices. clang warnings in v1.42 Issue #265 ocornut/imgui GitHub Java Type Casting (With Examples) - Programiz -1, Uggh. Can we typecast void into int? - Quora If the function had the correct signature you would not need to cast it explicitly. For a fairly recent compiler (that supports C99) you should not store or represent address as plain int value. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. */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. I agree passing a dynamically allocated pointer is fine (and I think the best way). The difference between the phonemes /p/ and /b/ in Japanese. c - Cast int to void* - Stack Overflow Hence there is no loss in data. 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. If int is no larger than pointer to void then one way to store the value is by simply copying the bytes: int i . To learn more, see our tips on writing great answers. 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. Well occasionally send you account related emails. this way I convert an int to a void* which is much better than converting a void* to an int. I assumed that gcc makes a 65536 out of my define, but I was wrong. Api says this is how i should create thread: So if I want to pass an int what I think I should do is: The second example assumes that a pointer is wide enough to store an int. You are right! void* to an array - C++ Forum - cplusplus.com If you need to keep the returned address, just keep it as void*. How to use Slater Type Orbitals as a basis functions in matrix method correctly? Here, the Java first converts the int type data into the double type. Casting and type conversions - C# Programming Guide Making statements based on opinion; back them up with references or personal experience. In C (int)b is called an explicit conversion, i.e. arrays - I get the error: "cast to smaller integer type 'int' from 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). Is pthread_join a must when using pthread in linux? How do I count the number of sentences in C using ". 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