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. 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. 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 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. The program can be set in such a way to ask the user to inform the type of data and . What is the point of Thrower's Bandolier? Find centralized, trusted content and collaborate around the technologies you use most. To learn more, see our tips on writing great answers. How do I set, clear, and toggle a single bit? reinterpret_cast is a type of casting operator used in C++. Not the answer you're looking for? Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. ", "? Before I update Xcode, my project still can build and run normally with all devices. Connect and share knowledge within a single location that is structured and easy to search. 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. 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). Thanks for contributing an answer to Stack Overflow! I assumed that gcc makes a 65536 out of my define, but I was wrong. And when assigning to a void pointer, all type information is lost. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. What is the purpose of non-series Shimano components? [that could be a TODO - not to delay solving the ICE]. You are correct, but cocos actually only uses that address as a unique id. If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. a cast of which the programmer should be aware of what (s)he is doing. you can just change architecture to support 32 bit compilation by all below in in Build Settings. @BlueMoon Thanks a lot! 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. Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin? 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. Acidity of alcohols and basicity of amines. 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 ) . Connect and share knowledge within a single location that is structured and easy to search. However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. How do I align things in the following tabular environment? 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. Find centralized, trusted content and collaborate around the technologies you use most. I would create a structure and pass that as void* to pthread_create. If pointers are 64 bits and ints are 32 bits, an int is too small to hold a pointer value. 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. Thank you all for your feedback. . The calculated expression consists of two operations. SCAN_PUT(ATTR, NULL); 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. 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. C99 defines the types "intptr_t" and "uintptr_t" which do . For example, the main thread could wait for all of the other threads to end before terminating. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Is a PhD visitor considered as a visiting scholar. How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. 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 use any other pointer, or you can use (size_t), which is 64 bits. What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? Basically its a better version of (void *)i.
There's no proper way to cast this to int in general case. Can I tell police to wait and call a lawyer when served with a search warrant? returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size);
Not the answer you're looking for? Already on GitHub? Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. Returns a value of type new-type. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Don't do that. To learn more, see our tips on writing great answers. An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. 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). privacy statement. how to cascade 2d int array to 2d void pointer array? Can Martian regolith be easily melted with microwaves? I'm using cocos2d-x-2.2.2. Connect and share knowledge within a single location that is structured and easy to search. 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. If that happens soon after the call to pthread_create() then you have a race condition, because there's a chance that the thread will attempt to read x's value after it's life has ended, which invokes undefined behavior. static_cast on the other hand should deny your stripping away the const qualifier. How to use Slater Type Orbitals as a basis functions in matrix method correctly? Asking for help, clarification, or responding to other answers. Why do small African island nations perform better than African continental nations, considering democracy and human development? STR34-C. What does it mean to convert int to void* or vice versa? But the problem has still happened. Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. Asking for help, clarification, or responding to other answers. If your standard library (even if it is not C99) happens to provide these types - use them. Issues. 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 how to print the thread id of 2d array argument? A void pointer can be really useful if the programmer is not sure about the data type of data inputted by the end user. reinterpret_cast<void *>(42)). Is it possible to create a concave light? Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. Sign in Functions return bigint only if the parameter expression is a bigint data type. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. 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. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. 1. Pull requests. If the value in a pointer is cast to a different type and it does not have the correct alignment for the new type, the behavior is undefined. If your standard library (even if it is not C99) happens to provide these types - use them. to your account, [87/252] Compiling C object lib/libopenvswitch.a.p/odp-util.c.obj In this case, casting the pointer back to an integer is meaningless, because . Star 675. It's always a good practice to put your #define's in brackets to avoid such surprise. 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. 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). The subreddit for the C programming language, Press J to jump to the feed. The difference between the phonemes /p/ and /b/ in Japanese. Now, what happens when I run it with the thread sanitizer? You use the address-of operator & to do that. 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. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? unsigned long call_fn = (unsigned long)FUNC; rev2023.3.3.43278. @DavidHeffernan I rephrased that sentence a little. Identify those arcade games from a 1983 Brazilian music video. Find centralized, trusted content and collaborate around the technologies you use most. Converts between types using a combination of implicit and user-defined conversions. -1, Uggh. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. You think by casting it here that you are avoiding the problem! This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. 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. Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. Why is this sentence from The Great Gatsby grammatical? 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. 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. Notifications. In C (int)b is called an explicit conversion, i.e. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). A nit: in your version, the cast to void * is unnecessary. static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. 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 the remaining integral types, the result is the value of the enum if it can be represented by the target type and unspecified otherwise. @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. 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. Casting arguments inside the function is a lot safer. Is it possible to create a concave light? ^~~~~~~~~~~~~~~~~~~~ Making statements based on opinion; back them up with references or personal experience. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' 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; x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. // 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. Hence there is no loss in data. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). The problem was there before, you just are being notified of it. ^~~~~~~~~~~~~~~~~~~~~ C / C++ Forums on Bytes. Note that it's not guaranteed that casting an, Generally this kind of type casting does not lead to any concern as long as the addresses are encoded using the same length as the "variable type" (. The preprocesor absolutely will not perform arithmetic. Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. for (i=0, j=0; j Michael Cole's Daughter,
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