By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Here, the Java first converts the int type data into the double type. should we also have a diagnostic for the (presumed) user error? Replacing broken pins/legs on a DIP IC package, How to handle a hobby that makes income in US. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); To subscribe to this RSS feed, copy and paste this URL into your RSS reader. "After the incident", I started to be more careful not to trip over things. Create an account to follow your favorite communities and start taking part in conversations. The cast back to int * is not, though. Yesterday, I updated Xcode to the newest version (5.1 (5B130a)) to compatible with iOS 7.1. 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. SCAN_PUT(ATTR, NULL); Please help me compile Chez Scheme. The main point is: a pointer has a platform dependent size. Use #include to define it. Can anybody explain how to pass an integer to a function which receives (void * ) as a parameter? -1, Uggh. rev2023.3.3.43278. STR34-C. If the function had the correct signature you would not need to cast it explicitly. What is the purpose of non-series Shimano components? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. return ((void **) returnPtr);} /* Matrix() */. ^~~~~~~~~~~~~~~~~~~ Once you manage to make this cast, then what?! I wish that you write those answer first than the explanation. And when assigning to a void pointer, all type information is lost. Making statements based on opinion; back them up with references or personal experience. ), For those who are interested. rev2023.3.3.43278. Actions. (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. 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. Casting a pointer to void* and back is valid use of reinterpret_cast<>. Asking for help, clarification, or responding to other answers. 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. I agree passing a dynamically allocated pointer is fine (and I think the best way). Whats the grammar of "For those whose stories they are"? 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 ) In the best case this will give the same results as the original code, with no advantages, but in the worst case it will fail in multiple catastrophic ways (type punning, endianness, less efficient, etc. Typically, long or unsigned long is . 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. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). this way I convert an int to a void* which is much better than converting a void* to an int. What is the difference between const int*, const int * const, and int const *? Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? This is what the second warning is telling you. To learn more, see our tips on writing great answers. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. 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). Does Counterspell prevent from any further spells being cast on a given turn? How can this new ban on drag possibly be considered constitutional? Where does this (supposedly) Gibson quote come from? Find centralized, trusted content and collaborate around the technologies you use most. If this is the data to a thread procedure, then you quite commonly want to pass by value. This is a fine way to pass integers to new pthreads, if that is what you need. AC Op-amp integrator with DC Gain Control in LTspice. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" 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. Put your define inside a bracket: without a problem. The text was updated successfully, but these errors were encountered: You signed in with another tab or window. Is it possible to create a concave light? Making statements based on opinion; back them up with references or personal experience. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' How Intuit democratizes AI development across teams through reusability. 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. But then you need to cast your arguments inside your thread function which is quite unsafe cf. 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. From the question I presume the OP does. pthread create managing values generated in function (in c), Establishing TCP socket connection between PHP client and C server on Ubuntu. Asking for help, clarification, or responding to other answers. Connect and share knowledge within a single location that is structured and easy to search. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. 471,961 Members | 900 Online. Such pointers can be stored in 32-bit data types (for instance, int, DWORD). A cast converts an object or value from one type to another. I'm using cocos2d-x-2.2.2. Error while setting app icon and launch image in xcode 5.1. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? Otherwise, if the original pointer value points to an object a, and there is an object b of the . What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Is it suspicious or odd to stand by the gate of a GA airport watching the planes? Just edited. A long long would not work for 32bit systems and a long would not work for 64 bit Windows (while 64bit Unix and Unix-like systems like OS X use the LP64 data model, in which a long is 64bit, 64bit Windows uses the LLP64 data model, in which a long has a size of 32bit (http://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models)). @BlueMoon Thanks a lot! Visit Microsoft Q&A to post new questions. That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? To be honest, I think, clang is too restrictive here. Making statements based on opinion; back them up with references or personal experience. 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 But gcc always give me a warning, that i cannot cast an int to a void*. Then i can continue compiling. // 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. ncdu: What's going on with this second size column? Why do academics stay as adjuncts for years rather than move around? you can pass the int value as void pointer like (void *)&n where n is integer, and in the function accept void pointer as parameter like void foo(void *n);and finally inside the function convert void pointer to int like, int num = *(int *)n;. SCAN_PUT_ATTR(key, ATTR, skey, FUNC); Bulk update symbol size units from mm to map units in rule-based symbology. The OP wanted to convert a pointer value to a int value, instead, most the answers, one way or the other, tried to wrongly convert the content of arg points to to a int value. A missing cast in the new fast > enumeration code. On many systems, an 8-bit unsigned int can be stored at any address while an unsigned 32-bit int must be aligned on an address that is a multiple of 4. [] 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). with ids being an array of ints and touch being a pointer. Pd = Pa; Similarly, Pc may be type cast to type int and assigned the value Pa. 1. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Setting a buffer of char* with intermediate casting to int*. rev2023.3.3.43278. (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. Implicit Type Conversion is also known as 'automatic type conversion'. How to use Slater Type Orbitals as a basis functions in matrix method correctly? 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" (. 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. Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. void* -> integer -> void* rather than integer -> void* -> integer. You can fix this error by replacing this line of code. If int is no larger than pointer to void then one way to store the value is by simply copying the bytes: int i . itch" "-I..\include\windows" "-Iinclude" "-I..\include" "-I..\datapath-windows\include" "-IC:\PTHREADS-BUILT\include" "-Xclang" "-fcolor-diagnostics" "-pipe" LLNL's tutorial is bad and they should feel bad. 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. I think the solution 3> should be the correct one. The difference between a and &a is the type. The subreddit for the C programming language, Press J to jump to the feed. A cast specifies a conversion from one type to another. This page was last modified on 12 February 2023, at 18:25. The only alternative is really to take time and fix all 64-bit code issues, of which there may be some non-trivial issues. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini I'm trying to learn pthreads and thing that keeps bugging me is how do i really pass argument to the function. 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. 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. Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. You think by casting it here that you are avoiding the problem! You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. The difference between the phonemes /p/ and /b/ in Japanese. C99 defines the types "intptr_t" and "uintptr_t" which do . this question. 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. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Note:You might receive a runtime exception if the pointer contains a value unsuitable for the context. . To subscribe to this RSS feed, copy and paste this URL into your RSS reader. In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. 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. 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. See also this documentation.. From and Into are generally intended to be lossless, infalliable conversions.as on the other hand can discard data and lead to bugs in some situations, for example casting a u64 to a usize may truncate the value on a 32-bit host. use $(ARCHS_STANDARD_32_BIT) at Architecture instead of $(ARCHS_STANDARD). Identify those arcade games from a 1983 Brazilian music video. 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). Converting one datatype into another is known as type casting or, type-conversion. Mutually exclusive execution using std::atomic? Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. 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. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. what does it mean to convert int to void* or vice versa? He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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! 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. (i.e. Java Type Casting. How create a simple program using threads in C? Why is there a voltage on my HDMI and coaxial cables? Cast characters to unsigned char before converting to larger integer sizes Created by Robert Seacord, last modified by Jill Britton on Oct 03, 2022 Signed character data must be converted to unsigned char before being assigned or converted to a larger signed type. This page has been accessed 1,655,678 times. How to convert a factor to integer\numeric without loss of information? Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul The correct answer is, if one does not mind losing data precision. How do I check if a string represents a number (float or int)? As a result of the integer division 3/2 we get the value 1, which is of the int type. a cast of which the programmer should be aware of what (s)he is doing. However even though their types are different, the address is going to be the same. You could use this code, and it would do the same thing as casting ptr to (char*). Again, all of the answers above missed the point badly. Wrong. ../lib/odp-util.c:5489:33: note: expanded from macro 'SCAN_PUT_ATTR' For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. 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. RNINGS" "-D_CRT_SECURE_NO_DEPRECATE" -MD -MQ lib/libopenvswitch.a.p/odp-util.c.obj -MF "lib\libopenvswitch.a.p\odp-util.c.obj.d" -o lib/libopenvswitch.a.p/od Half your pointer will be garbage. 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. privacy statement. Click to see the query in the CodeQL repository. So you know you can cast it back like this. Converting a void* to an int is non-portable way that may work or may not! @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. BUT converting a pointer to void* and back again is well supported (everywhere). Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. : iPhone Retina 4-inch 64-bit) is selected. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Instead of using a long cast, you should cast to size_t. Why do small African island nations perform better than African continental nations, considering democracy and human development? Or, they are all wrong. 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. I am compiling this program in linux gcc compiler.. Your first example is risky because you have to be very careful about the object lifetimes. 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; to the original pointer: The following type designates an unsigned integer type with the 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. SCAN_PUT_ATTR(mask, ATTR, smask, FUNC); static_cast on the other hand should deny your stripping away the const qualifier. Windows has 32 bit long only on 64 bit as well. 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. 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. Are there tables of wastage rates for different fruit and veg? Don't do that. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. (int) pthread_self() 64int48intuintptr_t (unsigned int) 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. then converted back to pointer to void, and the result will compare If your standard library (even if it is not C99) happens to provide these types - use them. 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. Hence there is no loss in data. The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. Sign in returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size);
You can use any other pointer, or you can use (size_t), which is 64 bits. For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. If the destination type is bool, this is a boolean conversion (see below). Is pthread_join a must when using pthread in linux? Type casting is when you assign a value of one primitive data type to another type. Not the answer you're looking for? There's no proper way to cast this to int in general case. How do I force make/GCC to show me the commands? Why does setupterm terminate the program? linux c-pthreads: problem with local variables. If any, how can the original function works without errors if we just ignore the warning. 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. What happens if you typecast as unsigned first? 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; ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] 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 Thanks. Therefore it is perfectly valid for the compiler to throw an error for a line like. 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; What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? And, most of these will not even work on gcc4. How do I set, clear, and toggle a single bit? SQL Server does not automatically promote . I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. All character types are to be converted to an integer. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. If pointers are 64 bits and ints are 32 bits, an int is too small to hold a pointer value. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. This is not even remotely "the correct answer". SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. It's an int type guaranteed to be big enough to contain a pointer. However, you are also casting the result of this operation to (void*). The result is the same as implicit conversion from the enum's underlying type to the destination type. In such condition type conversion (type promotion) takes place to avoid loss of data. Can Martian regolith be easily melted with microwaves? Connect and share knowledge within a single location that is structured and easy to search. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project?