cast to void *' from smaller integer type 'int

I'm only guessing here, but I think what you are supposed to do is actually pass the address of the variable to the function. To learn more, see our tips on writing great answers. 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. Cast unsigned char (uint8 *) pointer to unsigned long (uint32 *) pointer However, you are also casting the result of this operation to (void*). . Casting type int to const void* - C / C++ Yesterday, I updated Xcode to the newest version (5.1 (5B130a)) to compatible with iOS 7.1. Find centralized, trusted content and collaborate around the technologies you use most. Not the answer you're looking for? [Solved] Error "Cast from pointer to smaller type 'int' | 9to5Answer 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. Thanks. this way I convert an int to a void* which is much better than converting a void* to an int. 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. To avoid truncating your pointer, cast it to a type of identical size. The calculated expression consists of two operations. 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. Recovering from a blunder I made while emailing a professor. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. @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. How can this new ban on drag possibly be considered constitutional? Cast a smaller integer to a larger integer - community - The Rust Why does flowing off the end of a non-void function without returning a value not produce a compiler error? The following behavior-changing defect reports were applied retroactively to previously published C++ standards. error: cast from pointer to smaller type 'unsigned int' loses Can we typecast void into int? - Quora So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. There's no proper way to cast this to int in general case. You are getting warnings due to casting a void* to a type of a different size. How to correctly cast a pointer to int in a 64-bit application? C99 defines the types "intptr_t" and "uintptr_t" which do . Here is my code: I already tried (void*)M_TABLE_SIZE but then I get an error that I cannot use the * operator. I'm trying to create a void* from an int. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. 10) A prvalue of type pointer to void (possibly cv-qualified) can be converted to pointer to any object type. A cast converts an object or value from one type to another. Why is this sentence from The Great Gatsby grammatical? On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. Safe downcast may be done with dynamic_cast. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. How create a simple program using threads in C? This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. I need to cast the int from the first function so that I can use it as an argument for the second function. Or, they are all wrong. Any expression can be cast to type void (which means that the result of the expression is ignored), but it's not legal to cast an expression of type void to type int not least because the result of such a cast wouldn't make any sense. And in this context, it is very very very common to see programmers lazily type cast the. ^~~~~~~~~~~~~~~~~~~ INT31-C. Ensure that integer conversions do not result in lost or (int*)Pc = pa; After the execution of the above code all the three pointers, i.e., Pa, Pd, and Pc, point to the value 150. To learn more, see our tips on writing great answers. reinterpret_cast is a type of casting operator used in C++. What is the point of Thrower's Bandolier? On all of them int is 32bit, not 16bit. But gcc always give me a warning, that i cannot cast an int to a void*. 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 . But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. If the destination type is bool, this is a boolean conversion (see below). I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. @Shahbaz you could but I will not suggest to a C newbie to use globals. SCAN_PUT(ATTR, NULL); Just edited. As a result of the integer division 3/2 we get the value 1, which is of the int type. what does it mean to convert int to void* or vice versa? A cast specifies a conversion from one type to another. AC Op-amp integrator with DC Gain Control in LTspice. 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. should we also have a diagnostic for the (presumed) user error? I would create a structure and pass that as void* to pthread_create. 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. How to correctly cast a pointer to int in a 64-bit application? Casting type void to uint8_t - Arduino Forum B Programming Language | What is the History and Concept? Click to see the query in the CodeQL repository. Replacing broken pins/legs on a DIP IC package, AC Op-amp integrator with DC Gain Control in LTspice. This page has been accessed 1,655,678 times. 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. Use returnPtr[j] = (void *) ((long)ptr + i); ). On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. 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 windows meson: cast to smaller integer type 'unsigned long' from 'void In C (int)b is called an explicit conversion, i.e. An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. */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. Converting one datatype into another is known as type casting or, type-conversion. Is a PhD visitor considered as a visiting scholar. The subreddit for the C programming language, Press J to jump to the feed. this question. Using Kolmogorov complexity to measure difficulty of problems? Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. -1, Uggh. Pd = Pa; Similarly, Pc may be type cast to type int and assigned the value Pa. 1. ../lib/odp-util.c:5489:33: note: expanded from macro 'SCAN_PUT_ATTR' "I think what you should do is actually pass the address of the variable to the function" Not necessarily. Create an account to follow your favorite communities and start taking part in conversations. . However even though their types are different, the address is going to be the same. Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. Now, what happens when I run it with the thread sanitizer? The reinterpret_cast makes the int the size of a pointer and the warning will stop. Visit Microsoft Q&A to post new questions. Using indicator constraint with two variables. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. It is easier to understand and write than any other assembly language. If the source type is bool, the value false is converted to zero and the value true is converted to the value one of the destination type (note that if the destination type is int, this is an integer promotion, not an integer conversion). STR34-C. Cast characters to unsigned char before converting to larger 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 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. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. Wrong. Narrowing Casting (manually) - converting a larger type to a . Find centralized, trusted content and collaborate around the technologies you use most. return ((void **) returnPtr);} /* Matrix() */. If your standard library (even if it is not C99) happens to provide these types - use them. "because the type "int" supports only -32768 ~ 32768" This is not true for any modern desktop or mobile OS or any OS that is targeted by cocos2d-x. 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? 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. Identify those arcade games from a 1983 Brazilian music video. You need to pass an actual pointer. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. Type Casting in C Language with Examples - Dot Net Tutorials If you cast an int pointer int, you might get back a different integer. This is known as implicit type casting or type promotion, compiler automatically converts smaller data type to larger data type. You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : Yeah, the tutorial is doing it wrong. 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. 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). windows meson: cast to 'HANDLE' (aka 'void *') from smaller integer Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Connect and share knowledge within a single location that is structured and easy to search. this way you won't get any warning. Typically, long or unsigned long is . The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. Number Type Cast | Qt Forum If your standard library (even if it is not C99) happens to provide these types - use them. But assuming that it is, as long as the caller and the callee agree, you can do that sort of thing. [] 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). Bulk update symbol size units from mm to map units in rule-based symbology. I am an entry level C programmer. This page was last modified on 12 February 2023, at 18:25. What does casting to void* does when passing arguments to variadic functions? It is commonly called a pointer to T and its type is T*. So make sure you understand what you are doing! Note:You might receive a runtime exception if the pointer contains a value unsuitable for the context. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. I have looked around and can't seem to find any information on how to do this. That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. Why is there a voltage on my HDMI and coaxial cables? Don't do that. C++ how to get the address stored in a void pointer? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Use #include to define it. And then assign it to the double variable. I cannot reverse my upvote of user384706's answer, but it's wrong. Therefore it is perfectly valid for the compiler to throw an error for a line like. In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. Casting int to void* : r/C_Programming - reddit The pointer doesn't actually point to anything, but it's the result of an earlier cast from an integer to a pointer (e.g. for (i=0, j=0; jHow to correctly cast a pointer to int in a 64-bit application? Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? 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; We have to pass address of the variable to the function because in function definition argument is pointer variable. This is not even remotely "the correct answer". eg. Since gcc compiles that you are performing arithmetic between void* and an int (1024). ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' 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. Asking for help, clarification, or responding to other answers. Find centralized, trusted content and collaborate around the technologies you use most. Returns a value of type new-type. I think the solution 3> should be the correct one. FAILED: lib/libopenvswitch.a.p/odp-util.c.obj c - Cast int to void* - Stack Overflow 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. The difference between the phonemes /p/ and /b/ in Japanese. Java Type Casting (With Examples) - Programiz @BlueMoon Thanks a lot! ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] This allows you to reinterpret the void * as an int. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). To subscribe to this RSS feed, copy and paste this URL into your RSS reader. It's an int type guaranteed to be big enough to contain a pointer. that any valid pointer to void can be converted to this type, then @Martin York: No, it doesn't depend on endiannness. byte -> short -> char -> int -> long -> float -> double. Are there tables of wastage rates for different fruit and veg? warning C4311: 'type cast': pointer truncation from 'void *' to 'long' in ECPG test files. Is it possible to create a concave light? A missing cast in the new fast > enumeration code. 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. Here is some piece of code where that error occur: /cocos2d-x-2.2.2/cocos2dx/platform/ios/EAGLView.mm:408:18: Cast from pointer to smaller type 'int' loses information. [that could be a TODO - not to delay solving the ICE]. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); Cast Operations - Oracle The program can be set in such a way to ask the user to inform the type of data and . // 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. Can Martian regolith be easily melted with microwaves? To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. actually no, as int my be a smaller type than a pointer ;-) But, of course with int64_t it works fine. For integer casts in specific, using into() signals that . You are getting warnings due to casting a void* to a type of a different size. Why do small African island nations perform better than African continental nations, considering democracy and human development? It is purely a compile-time directive which instructs the compiler to treat expression as if it had . Half your pointer will be garbage. Not the answer you're looking for? ", "!"? (int) pthread_self() 64int48intuintptr_t (unsigned int) Therefore, you need to change it to long long instead of long in windows for 64 bits. If the value is ever used as pointer again that will prove to be an extremely bad idea. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. The cast back to int * is not, though. You think by casting it here that you are avoiding the problem! @DietrichEpp can you explain what is race condition with using. Issues. 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. ERROR: incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int', error: cast to 'string' (aka 'char *') from smaller integer type 'int' [-Werror,-Wint-to-pointer-cast], error: incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int' C, warning: initialization of 'unsigned char' from 'uint8_t *' {aka 'unsigned char *'} makes integer from pointer without a cast [-Wint-conversion], Minimising the environmental effects of my dyson brain. This is flat out wrong. 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. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; This is why you got Error 1 C2036, from your post. ), For those who are interested. How to use Slater Type Orbitals as a basis functions in matrix method correctly? Disconnect between goals and daily tasksIs it me, or the industry? 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. In such condition type conversion (type promotion) takes place to avoid loss of data. Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). However the actual code in question contains an explicit c-style cast to int. Connect and share knowledge within a single location that is structured and easy to search. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. Using an integer address (like &x) is probably wrong, indeed each modification you will execute on x will affect the pass behaviour. casting from int to void* and back to int. rev2023.3.3.43278. [mst-vhost:vhost 5/52] drivers/block/virtio_blk.c:539:21: warning I agree passing a dynamically allocated pointer is fine (and I think the best way). ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' The int data type is the primary integer data type in SQL Server. (void *)i Error: cast to 'void *' from smaller integer type 'int' PS: UBUNTUCLANG3.5 clang -O0 -std=gnu11 -march=native -lm -lpthread pagerank.c -o pagerank c pthreads 4 10.3k 2 21 2015-06-05 How do I force make/GCC to show me the commands? INT36-C. Converting a pointer to integer or integer to pointer cast to 'void *' from smaller integer type 'int' Notifications. ../lib/odp-util.c:5601:9: note: expanded from macro 'SCAN_PUT' How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. long guarantees a pointer size on Linux on any machine. 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.. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. (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. How Intuit democratizes AI development across teams through reusability. 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. Connect and share knowledge within a single location that is structured and easy to search. Casting an open pointer to other pointer types and casting other pointer types to an open pointer does not result in a compile time error. That's not a good idea if the original object (that was cast to void*) was an integer. 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. @jackdoe: It's a waste of human life to write code that "you may need in the future". Casting Pointers - IBM Using printf with a pointer to float gives an error, Meaning of int (*) (int *) = 5 (or any integer value), Casting int to void* loses precision, and what is the solution in required cases, Acidity of alcohols and basicity of amines. This will only compile if the destination type is long enough. The preprocessor will replace your code by this: This is unlikely what you are trying to do. What happens if you typecast as unsigned first? The text was updated successfully, but these errors were encountered:

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