What happens if you typecast as unsigned first? And, most of these will not even work on gcc4. 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;. However, you are also casting the result of this operation to (void*). Instead of using a long cast, you should cast to size_t. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. For the remaining integral types, the result is the value of the enum if it can be represented by the target type and unspecified otherwise. Can Martian regolith be easily melted with microwaves? Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" // 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. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. 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 . Visit Microsoft Q&A to post new questions. A cast specifies a conversion from one type to another. It is easier to understand and write than any other assembly language. 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;. C / C++ Forums on Bytes. should we also have a diagnostic for the (presumed) user error? How can this new ban on drag possibly be considered constitutional? To learn more, see our tips on writing great answers. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, error: cast from void* to int loses precision, cast to pointer from integer of different size, pthread code. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. Not the answer you're looking for? Here is my code: I already tried (void*)M_TABLE_SIZE but then I get an error that I cannot use the * operator. You can only do this if you use a synchronization primitive to ensure that there is no race condition. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' 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. If pointers are 64 bits and ints are 32 bits, an int is too small to hold a pointer value. Thanks for contributing an answer to Stack Overflow! How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? 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. . If int is no larger than pointer to void then one way to store the value is by simply copying the bytes: int i . It's always a good practice to put your #define's in brackets to avoid such surprise. The most general answer is - in no way. Connect and share knowledge within a single location that is structured and easy to search. @Martin York: No, it doesn't depend on endiannness. It is purely a compile-time directive which instructs the compiler to treat expression as if it had . 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. you can just change architecture to support 32 bit compilation by all below in in Build Settings. A void pointer can be really useful if the programmer is not sure about the data type of data inputted by the end user. Why do small African island nations perform better than African continental nations, considering democracy and human development? 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. This solution is in accordance with INT18-C. Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. The value of float variable is= 37.75. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? 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. It was derived from the BCPL, and the name of the b language is possibly from the BCPL contraction. What I am trying to emphasis that conversion from int to pointer and back again can be frough with problems as you move from platform to platform. You can fix this error by replacing this line of code. GitHub. what does it mean to convert int to void* or vice versa? Can anybody explain how to pass an integer to a function which receives (void * ) as a parameter? Is pthread_join a must when using pthread in linux? Is it possible to create a concave light? Typically, long or unsigned long is . 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. Does Counterspell prevent from any further spells being cast on a given turn? Therefore it is perfectly valid for the compiler to throw an error for a line like. Get the address of a callback function to call dynamically in C++, error: call of overloaded function ambiguous, error: cast from to unsigned int loses precision [-fpermissive]. The problem just occur with Xcode 5.1. If your standard library (even if it is not C99) happens to provide these types - use them. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. How to use Slater Type Orbitals as a basis functions in matrix method correctly? Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul 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. A nit: in your version, the cast to void * is unnecessary. Why does setupterm terminate the program? The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. SCAN_PUT_ATTR(key, ATTR, skey, FUNC); what happens when we typecast normal variable to void* or any pointer variable? @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? 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. B programing language is a language based on basic combined programming or a BCPL, and it is the precursor of the C programming language. C/C++ , Cerror: cast to 'void *' from smaller integer type 'int'. 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. how to cascade 2d int array to 2d void pointer array? Disconnect between goals and daily tasksIs it me, or the industry? 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. (int) pthread_self() 64int48intuintptr_t (unsigned int) If any, how can the original function works without errors if we just ignore the warning. Hence there is no loss in data. Most answers just try to extract 32 useless bits out of the argument. Connect and share knowledge within a single location that is structured and easy to search. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini No idea how it amassed 27 upvotes?! Once you manage to make this cast, then what?! Replacing broken pins/legs on a DIP IC package, How to handle a hobby that makes income in US. Do new devs get fired if they can't solve a certain bug? For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. All character types are to be converted to an integer. I am compiling this program in linux gcc compiler.. And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. 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). Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. The result is the same as implicit conversion from the enum's underlying type to the destination type. Already on GitHub? ), Styling contours by colour and by line thickness in QGIS. Find centralized, trusted content and collaborate around the technologies you use most. this question. Notifications. @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. The difference between the phonemes /p/ and /b/ in Japanese. a is of type int[4], which can be implicitly cast to int* (ie, a pointer to an int) &a is of type int(*)[4] (ie: a pointer to an array of 4 ints). 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. lexborisov Modest Public. As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). The preprocessor will replace your code by this: This is unlikely what you are trying to do. This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. It solved my problem too. reinterpret_cast<void *>(42)). By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. *PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type warning @ 2023-01-23 13:28 Hans de Goede 2023-01-23 13:56 ` Hans de Goede 0 siblings, 1 reply; 2+ messages in thread From: Hans de Goede @ 2023-01-23 13:28 UTC (permalink / raw) To: Mark Gross Cc: Hans de Goede, Andy Shevchenko, platform-driver-x86, kernel test robot Fix the following . You need to pass an actual pointer. How to convert a factor to integer\numeric without loss of information? Noncompliant Code Example (memset())For historical reasons, certain C Standard functions accept an argument of type int and convert it to either unsigned char or plain char. What is the point of Thrower's Bandolier? Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Setting a buffer of char* with intermediate casting to int*. "After the incident", I started to be more careful not to trip over things. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; But assuming that it is, as long as the caller and the callee agree, you can do that sort of thing. 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. What does it mean to convert int to void* or vice versa? } SCAN_END_SINGLE(ATTR) As a result of the integer division 3/2 we get the value 1, which is of the int type. The int data type is the primary integer data type in SQL Server. 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. long guarantees a pointer size on Linux on any machine. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? Whats the grammar of "For those whose stories they are"? Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. It is done by the compiler on its own, without any external trigger from the user. 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. [that could be a TODO - not to delay solving the ICE]. In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. to your account, [87/252] Compiling C object lib/libopenvswitch.a.p/odp-util.c.obj Not the answer you're looking for? 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. I'm using cocos2d-x-2.2.2. To learn more, see our tips on writing great answers. How do I set, clear, and toggle a single bit? 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. Where does this (supposedly) Gibson quote come from? pthread passes the argument as a void*. x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. 1. It's an int type guaranteed to be big enough to contain a pointer. What does casting to void* does when passing arguments to variadic functions? Mutually exclusive execution using std::atomic? I wish that you write those answer first than the explanation. @Shahbaz you could but I will not suggest to a C newbie to use globals. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. If you need to keep the returned address, just keep it as void*. Star 675. How create a simple program using threads in C? If you convert (void*) to (long) no precision is lost, then by assigning the (long) to an (int), it properly truncates the number to fit. On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. Find centralized, trusted content and collaborate around the technologies you use most. This is what the second warning is telling you. 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. This page was last modified on 12 February 2023, at 18:25. Type casting is when you assign a value of one primitive data type to another type. Find centralized, trusted content and collaborate around the technologies you use most. If your standard library (even if it is not C99) happens to provide these types - use them. Just re-enforcing the old behavior of Xcode 5.0 and earlier versions, that already cut away parts of the address by casting it to int, won't introduce any new bugs and avoids the need to learn and understand lots of implementation-internal cocos code. Such pointers can be stored in 32-bit data types (for instance, int, DWORD). 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. Can I tell police to wait and call a lawyer when served with a search warrant? What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? I have a two functions, one that returns an int, and one that takes a const void* as an argument. rev2023.3.3.43278. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. For integer casts in specific, using into() signals that . Converts between types using a combination of implicit and user-defined conversions. 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. privacy statement. @DavidHeffernan I rephrased that sentence a little. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. 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" (. 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. ), For those who are interested. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? STR34-C. I'm trying to learn pthreads and thing that keeps bugging me is how do i really pass argument to the function. 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". Taking the above declarations of A, D, ch of the . Put your define inside a bracket: without a problem. 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. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? "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. The subreddit for the C programming language, Press J to jump to the feed. How can this new ban on drag possibly be considered constitutional? You should perform type conversion based on 64bit build system because the type "int" supports only -32768 ~ 32768. 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 [.]) Maybe you can try this too. What is the difference between const int*, const int * const, and int const *? 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. You could use this code, and it would do the same thing as casting ptr to (char*). 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. ../lib/odp-util.c:5601:9: note: expanded from macro 'SCAN_PUT' So,solution #3 works just fine. *sound/soc/codecs/tlv320aic32x4.c:1202:18: warning: cast to smaller integer type 'enum aic32x4_type' from 'void *' @ 2022-04-22 9:48 kernel test robot 0 siblings, 0 . 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 is there a voltage on my HDMI and coaxial cables? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Have a question about this project? 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. This is a fine way to pass integers to new pthreads, if that is what you need. 10) A prvalue of type pointer to void (possibly cv-qualified) can be converted to pointer to any object type. Infact I know several systems where that does not hold. No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. 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. ^~~~~~~~~~~~~~~~~~~~ By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Identify those arcade games from a 1983 Brazilian music video. Using indicator constraint with two variables. error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? 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. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. I personally upvoted this answer because by it's first line of text it helped me to understand the reason of this strange error message and what am I, poor idiot, doing :D. Not valid on Windows 64 - long is still 32-bit but pointers are 64-bit. Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. ncdu: What's going on with this second size column? Just edited. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. warning C4311: 'type cast': pointer truncation from 'void *' to 'long' in ECPG test files. this way I convert an int to a void* which is much better than converting a void* to an int. p-util.c.obj "-c" ../lib/odp-util.c This is flat out wrong. vegan) just to try it, does this inconvenience the caterers and staff? ^~~~~~~~~~~~~~~~~~~ An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. Basically its a better version of (void *)i. What you do here is undefined behavior, and undefined behavior of very practical sort. : iPhone Retina 4-inch 64-bit) is selected. Not the answer you're looking for? Yeah, the tutorial is doing it wrong.
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