I have looked around and can't seem to find any information on how to do this. 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. [PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type warning GitHub. This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). cast to 'void *' from smaller integer type 'int' Otherwise, if the original pointer value points to an object a, and there is an object b of the . . Connect and share knowledge within a single location that is structured and easy to search. If your standard library (even if it is not C99) happens to provide these types - use them. The correct answer is, if one does not mind losing data precision. But gcc always give me a warning, that i cannot cast an int to a void*. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Is a PhD visitor considered as a visiting scholar. Not the answer you're looking for? Find centralized, trusted content and collaborate around the technologies you use most. Using Kolmogorov complexity to measure difficulty of problems? this way you won't get any warning. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. [] 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). 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 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". 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. C / C++ Forums on Bytes. Once you manage to make this cast, then what?! Types - D Programming Language It is easier to understand and write than any other assembly language. Therefore it is perfectly valid for the compiler to throw an error for a line like. That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. Since gcc compiles that you are performing arithmetic between void* and an int (1024). Thanks for contributing an answer to Stack Overflow! You can only do this if you use a synchronization primitive to ensure that there is no race condition. As a result of the integer division 3/2 we get the value 1, which is of the int type. 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. c - type casting integer to void* - Stack Overflow Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. Thanks for contributing an answer to Stack Overflow! 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. If you cast an int pointer int, you might get back a different integer. Now, what happens when I run it with the thread sanitizer? To learn more, see our tips on writing great answers. Type Casting in C Language with Examples - Dot Net Tutorials This is known as implicit type casting or type promotion, compiler automatically converts smaller data type to larger data type. Recovering from a blunder I made while emailing a professor. Compile error on Android ARM Issue #163 cisco/ChezScheme cast to void *' from smaller integer type 'int By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. I would create a structure and pass that as void* to pthread_create. Most answers just try to extract 32 useless bits out of the argument. Thanks. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. 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. C - Type Casting - tutorialspoint.com Bulk update symbol size units from mm to map units in rule-based symbology. FAILED: lib/libopenvswitch.a.p/odp-util.c.obj When is casting void pointer needed in C? 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. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? SCAN_PUT(ATTR, NULL); Implicit conversions - cppreference.com However, you are also casting the result of this operation to (void*). 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. The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. Remarks. It is done by the compiler on its own, without any external trigger from the user. You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : rev2023.3.3.43278. If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? STR34-C. The value of float variable is= 37.75. Press question mark to learn the rest of the keyboard shortcuts. Thanks for pointing that out. How can this new ban on drag possibly be considered constitutional? Asking for help, clarification, or responding to other answers. @jackdoe: It's a waste of human life to write code that "you may need in the future". Thus as a result it may be less error prone to generate a pointer dynamcially and use that. reinterpret_cast<void *>(42)). @DietrichEpp can you explain what is race condition with using. 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. Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. 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. Put your define inside a bracket: without a problem. If your standard library (even if it is not C99) happens to provide these types - use them. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); Making statements based on opinion; back them up with references or personal experience. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? It's always a good practice to put your #define's in brackets to avoid such surprise. @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. 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. To avoid truncating your pointer, cast it to a type of identical size. The difference between a and &a is the type. Just edited. A cast converts an object or value from one type to another. Just want to point out that the purpose of threads is, +1 absolutely true, but if you take you time to write struct {}, you can save a lot of troubles in the future when you want to receive/send more data then just an int. converted back to pointer to void, and the result will compare equal Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin? SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Functions return bigint only if the parameter expression is a bigint data type. to the original pointer: The following type designates an unsigned integer type with the 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). I'm trying to create a void* from an int. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Since all pointers on 64-bit Windows are 64 bits, you are growing the data size from 32 bits backto 64 bits. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ If this is the data to a thread procedure, then you quite commonly want to pass by value. In this case, casting the pointer back to an integer is meaningless, because . 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! In such condition type conversion (type promotion) takes place to avoid loss of data. C++ Tutorial => Conversion between pointer and integer It is commonly called a pointer to T and its type is T*. what does it mean to convert int to void* or vice versa? How to use Slater Type Orbitals as a basis functions in matrix method correctly? What is the point of Thrower's Bandolier? My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? ", "? C++ how to get the address stored in a void pointer? Error while setting app icon and launch image in xcode 5.1. Number Type Cast | Qt Forum "I think what you should do is actually pass the address of the variable to the function" Not necessarily. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. Why is this sentence from The Great Gatsby grammatical? There is absolutely not gurantee that sizeof(int) <= sizeof(void*). property that any valid pointer to void can be converted to this type, */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; 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. Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer.