cast to void *' from smaller integer type 'int

A sane compiler may throw a warning on lines like this but by no way it should throw an error, because this code is NOT wrong, it is just potentially error-prone, but can be perfectly valid. Mutually exclusive execution using std::atomic? It generally takes place when in an expression more than one data type is present. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. Acidity of alcohols and basicity of amines. Netdev Archive on lore.kernel.org help / color / mirror / Atom feed * [mst-vhost:vhost 5/52] drivers/block/virtio_blk.c:539:21: warning: assignment to 'void *' from . No idea how it amassed 27 upvotes?! Why do small African island nations perform better than African continental nations, considering democracy and human development? Instead of using a long cast, you should cast to size_t. Mutually exclusive execution using std::atomic? unsigned long call_fn = (unsigned long)FUNC; 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. A missing cast in the new fast > enumeration code. Floating-point conversions 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. 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. Where does this (supposedly) Gibson quote come from? 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. If pointers are 64 bits and ints are 32 bits, an int is too small to hold a pointer value. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. ^~~~~~~~~~~~~~~~~~~~~ The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. 1. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. ^~~~~~~~~~~~~~~~~~~~ Click to see the query in the CodeQL repository. This solution is in accordance with INT18-C. How can this new ban on drag possibly be considered constitutional? The correct answer is, if one does not mind losing data precision. Press question mark to learn the rest of the keyboard shortcuts. Type casting is when you assign a value of one primitive data type to another type. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? You use the address-of operator & to do that. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. A cast specifies a conversion from one type to another. There's no proper way to cast this to int in general case. Are there tables of wastage rates for different fruit and veg? Visit Microsoft Q&A to post new questions. The proper way is to cast it to another pointer type. How create a simple program using threads in C? 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". 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. 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. windows meson: cast to smaller integer type 'unsigned long' from 'void *'. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? If you preorder a special airline meal (e.g. you can just change architecture to support 32 bit compilation by all below in in Build Settings. rev2023.3.3.43278. Terrible solution. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. Thanks for contributing an answer to Stack Overflow! "-I.." "-Iinclude\openflow" "-I..\include\openflow" "-Iinclude\openvswitch" "-I..\include\openvsw 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. How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? Don't do that. that any valid pointer to void can be converted to this type, then byte -> short -> char -> int -> long -> float -> double. Why is there a voltage on my HDMI and coaxial cables? What is the difference between const int*, const int * const, and int const *? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. STR34-C. Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. There are ways to prevent this: pass a dynamic allocated argument if your not the passing thread is not static or if your argument is a local variable, otherwise there is no issue. And when assigning to a void pointer, all type information is lost. The following behavior-changing defect reports were applied retroactively to previously published C++ standards. 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. Use returnPtr[j] = (void *) ((long)ptr + i); ). Does a summoned creature play immediately after being summoned by a ready action? My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Keep in mind that thrArg should exist till the myFcn() uses it. Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? 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. Put your define inside a bracket: without a problem. I'm using cocos2d-x-2.2.2. ^~~~~~~~~~~~~~~~~~~~ To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. It's an int type guaranteed to be big enough to contain a pointer. 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. rev2023.3.3.43278. It is commonly called a pointer to T and its type is T*. In such condition type conversion (type promotion) takes place to avoid loss of data. reinterpret_cast<void *>(42)). To avoid truncating your pointer, cast it to a type of identical size. how to cascade 2d int array to 2d void pointer array? 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" (. Using Kolmogorov complexity to measure difficulty of problems? How to use Slater Type Orbitals as a basis functions in matrix method correctly? equal to the original pointer: First you are using a define, which is not a variable. Bulk update symbol size units from mm to map units in rule-based symbology. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? LLNL's tutorial is bad and they should feel bad. That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. privacy statement. This will only compile if the destination type is long enough. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? The reinterpret_cast makes the int the size of a pointer and the warning will stop. This page was last modified on 12 February 2023, at 18:25. It is easier to understand and write than any other assembly language. However, you are also casting the result of this operation to (void*). Connect and share knowledge within a single location that is structured and easy to search. Does Counterspell prevent from any further spells being cast on a given turn? Connect and share knowledge within a single location that is structured and easy to search. Converts between types using a combination of implicit and user-defined conversions. Thanks. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. I get the error: "cast to smaller integer type 'int' from 'string' (aka 'char *')" referencing line of code: while (isalpha(residents[i].name) == 0), How Intuit democratizes AI development across teams through reusability. this question. error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. To learn more, see our tips on writing great answers. Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. 471,961 Members | 900 Online. So make sure you understand what you are doing! On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. What happens if you typecast as unsigned first? Whats the grammar of "For those whose stories they are"? 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. Identify those arcade games from a 1983 Brazilian music video, Relation between transaction data and transaction id, The difference between the phonemes /p/ and /b/ in Japanese. For a fairly recent compiler (that supports C99) you should not store or represent address as plain int value. Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. Referring to N1570 7.20.1.4/p1 (Integer types capable of holding object pointers): The following type designates a signed integer type with the property I wish that you write those answer first than the explanation.