What is the point of Thrower's Bandolier? If you cast an int pointer int, you might get back a different integer. The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. 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. This is flat out wrong. Difficulties with estimation of epsilon-delta limit proof. rev2023.3.3.43278. 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. this way I convert an int to a void* which is much better than converting a void* to an int. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Thanks for contributing an answer to Stack Overflow! So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. The mapping in pointer<->integer casts is implementation defined, but the intent was that if the pointer type is large enough and isn't forcefully aligned (, But that's different. 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. Acidity of alcohols and basicity of amines. Maybe you can try this too. 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. actually no, as int my be a smaller type than a pointer ;-) But, of course with int64_t it works fine. This page has been accessed 1,655,678 times. */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; 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. Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. 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; Connect and share knowledge within a single location that is structured and easy to search. XCode 5.1 is change all architecture to 64 bit. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Making statements based on opinion; back them up with references or personal experience. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. what does it mean to convert int to void* or vice versa? Why does Mister Mxyzptlk need to have a weakness in the comics? Well occasionally send you account related emails. Yesterday, I updated Xcode to the newest version (5.1 (5B130a)) to compatible with iOS 7.1. 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;. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Is a PhD visitor considered as a visiting scholar. 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. And in this context, it is very very very common to see programmers lazily type cast the. Your first example is risky because you have to be very careful about the object lifetimes. ^~~~~~~~~~~~~~~~~~~ Can Martian regolith be easily melted with microwaves? 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. I have a two functions, one that returns an int, and one that takes a const void* as an argument. The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. This page was last modified on 12 February 2023, at 18:25. then converted back to pointer to void, and the result will compare You should perform type conversion based on 64bit build system because the type "int" supports only -32768 ~ 32768. Already on GitHub? That could create all kinds of trouble. reinterpret_cast<void *>(42)). I am compiling this program in linux gcc compiler.. 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. 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. 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. 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. Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. 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. Then I build my project, I get the error "Cast from pointer to smaller type 'int' loses information" in EAGLView.mm file (line 408) when 64-bit simulators (e.g. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Returns a value of type new-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 : An open (void) pointer can hold a pointer of any type. As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). Any help with this is appreciated. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? 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. This is not a conversion at all. C/C++ , Cerror: cast to 'void *' from smaller integer type 'int'. If you preorder a special airline meal (e.g. Pd = Pa; Similarly, Pc may be type cast to type int and assigned the value Pa. 1. 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. use $(ARCHS_STANDARD_32_BIT) at Architecture instead of $(ARCHS_STANDARD). "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 can use any other pointer, or you can use (size_t), which is 64 bits. /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. This is what the second warning is telling you. I'm unfamiliar with XCode, but the solution should be something like follows: Most of the "solutions" above can lose part of the pointer address when casting to a smaller type. Why is there a voltage on my HDMI and coaxial cables? A nit: in your version, the cast to void * is unnecessary. How to correctly cast a pointer to int in a 64-bit application? It is commonly called a pointer to T and its type is T*. You could use this code, and it would do the same thing as casting ptr to (char*). How to notate a grace note at the start of a bar with lilypond? Find centralized, trusted content and collaborate around the technologies you use most. SCAN_PUT(ATTR, NULL); By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Why did Ukraine abstain from the UNHRC vote on China? Why is there a voltage on my HDMI and coaxial cables? Floating-point conversions (void *)i Error: cast to 'void *' from smaller integer type 'int'. Star 675. Properly casting a `void*` to an integer in C++ 24,193 Solution 1 I think using intptr_t is the correct intermediate here, since it's guaranteed to be large enough to contain the integral value of the void*, and once I have an integer value I can then truncate it without causing the compiler to complain. The difference between the phonemes /p/ and /b/ in Japanese. What is the point of Thrower's Bandolier? 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; This will only compile if the destination type is long enough. Yeah, the tutorial is doing it wrong. to the original pointer: The following type designates an unsigned integer type with the In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. 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. rev2023.3.3.43278. 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. Based on the design of this function, which modification is right. Pull requests. rev2023.3.3.43278. The problem is not with casting, but with the target type loosing half of the pointer. Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. 10) A prvalue of type pointer to void (possibly cv-qualified) can be converted to pointer to any object type. The reinterpret_cast makes the int the size of a pointer and the warning will stop. LLNL's tutorial is bad and they should feel bad. C++ how to get the address stored in a void pointer? But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. But assuming that it is, as long as the caller and the callee agree, you can do that sort of thing. 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 are getting warnings due to casting a void* to a type of a different size. (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. The result is the same as implicit conversion from the enum's underlying type to the destination type. A nit: in your version, the cast to void * is unnecessary. Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. Connect and share knowledge within a single location that is structured and easy to search. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' Update: Today, i download the latest version of cocos2d-x (cocos2d-x 2.2.3). equal to the original pointer: First you are using a define, which is not a variable. how to cascade 2d int array to 2d void pointer array? lexborisov Modest Public. You may declare a const int variable and cast its reference to the void*. The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS, AC Op-amp integrator with DC Gain Control in LTspice, Identify those arcade games from a 1983 Brazilian music video. Find centralized, trusted content and collaborate around the technologies you use most. Connect and share knowledge within a single location that is structured and easy to search. static_cast on the other hand should deny your stripping away the const qualifier. Getting Command /bin/sh failed with exit code 65 Error with Xcode 5.1 . How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? 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" (. . I'm trying to create a void* from an int. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); 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. If int is no larger than pointer to void then one way to store the value is by simply copying the bytes: int i . He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. 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 program can be set in such a way to ask the user to inform the type of data and . 471,961 Members | 900 Online. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? converted back to pointer to void, and the result will compare equal Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Can anybody explain how to pass an integer to a function which receives (void * ) as a parameter? Using Kolmogorov complexity to measure difficulty of problems? Safe downcast may be done with dynamic_cast. All float types are to be converted to double. If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. 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. This is why you got Error 1 C2036, from your post. */ >> -bool >> +enum conversion_safety >> unsafe_conversion_p (tree type, tree expr, bool . 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. Don't do that. For a fairly recent compiler (that supports C99) you should not store or represent address as plain int value. Note the difference between the type casting of a variable and type casting of a pointer. 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). Fork 63. Thanks for contributing an answer to Stack Overflow! Api says this is how i should create thread: So if I want to pass an int what I think I should do is: The second example assumes that a pointer is wide enough to store an int. 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. To learn more, see our tips on writing great answers. [] 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). 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. 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. Mutually exclusive execution using std::atomic? In the case of Widening Type Casting, the lower data type (having smaller size) is converted into the higher data type (having larger size). The cast back to int * is not, though. I assumed that gcc makes a 65536 out of my define, but I was wrong. While working with Threads in C, I'm facing the warning, "warning: cast to pointer from integer of different size". (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. A pointer converted to an integer of sufficient size and back to the same pointer type is guaranteed to have its original value, otherwise the resulting pointer cannot be dereferenced safely ( the round-trip conversion in the opposite direction is not guaranteed [.]) The following behavior-changing defect reports were applied retroactively to previously published C++ standards. This solution is in accordance with INT18-C. rev2023.3.3.43278. How can this new ban on drag possibly be considered constitutional? If the function had the correct signature you would not need to cast it explicitly. What is the difference between const int*, const int * const, and int const *? And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. So you know you can cast it back like this. It is done by the compiler on its own, without any external trigger from the user. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] Not the answer you're looking for? This is not even remotely "the correct answer". Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Infact I know several systems where that does not hold. cast operators [edit] When an expression is used in the context where a value of a different type is expected, conversionmay occur: intn =1L;// expression 1L has type long, int is expectedn =2.1;// expression 2.1 has type double, int is expectedchar*p =malloc(10);// expression malloc(10) has type void*, char* is expected 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! Why do academics stay as adjuncts for years rather than move around? . Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. 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). Otherwise, if the original pointer value points to an object a, and there is an object b of the . -1, Uggh. I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. Where does this (supposedly) Gibson quote come from? Asking for help, clarification, or responding to other answers. Create an account to follow your favorite communities and start taking part in conversations. So,solution #3 works just fine. How to convert a factor to integer\numeric without loss of information? To learn more, see our tips on writing great answers. 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). How to get the error message from the error code returned by GetLastError()? The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. reinterpret_cast is a type of casting operator used in C++. Does Counterspell prevent from any further spells being cast on a given turn? An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. C99 defines the types "intptr_t" and "uintptr_t" which do . Are there tables of wastage rates for different fruit and veg? To learn more, see our tips on writing great answers. Actions. Is it possible to create a concave light? What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. 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. SCAN_PUT_ATTR(mask, ATTR, smask, FUNC); Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? ^~~~~~~~~~~~~~~~~~~~ Not the answer you're looking for? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); Here, the Java first converts the int type data into the double type. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Why is this sentence from The Great Gatsby grammatical? A missing cast in the new fast > enumeration code. what happens when we typecast normal variable to void* or any pointer variable? What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. I understood, but that would introduce dynamic memory and ugly lifetime issues (an object allocated by one thread must be freed by some other) - all just to pass an. If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. (int) pthread_self() 64int48intuintptr_t (unsigned int) you can just change architecture to support 32 bit compilation by all below in in Build Settings. SCAN_PUT(ATTR, NULL); I am an entry level C programmer. Find centralized, trusted content and collaborate around the technologies you use most. Instead of using a long cast, you should cast to size_t. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. You can only do this if you use a synchronization primitive to ensure that there is no race condition. It generally takes place when in an expression more than one data type is present. 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
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