Maybe you can try this too. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. 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. [Solved] Properly casting a `void*` to an integer in C++ You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : error: cast from pointer to smaller type 'unsigned int' loses information. If this is the data to a thread procedure, then you quite commonly want to pass by value. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. 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. what happens when we typecast normal variable to void* or any pointer variable? Implicit conversions - cppreference.com The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. Actions. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Taking the above declarations of A, D, ch of the . 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! INT31-C. Ensure that integer conversions do not result in lost or What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Not the answer you're looking for? Thanks. What happens if you typecast as unsigned first? Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Your first example is risky because you have to be very careful about the object lifetimes. Making statements based on opinion; back them up with references or personal experience. You should perform type conversion based on 64bit build system because the type "int" supports only -32768 ~ 32768. 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. 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. If pointers are 64 bits and ints are 32 bits, an int is too small to hold a pointer value. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. By clicking Sign up for GitHub, you agree to our terms of service and /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. Most answers just try to extract 32 useless bits out of the argument. Infact I know several systems where that does not hold. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. : iPhone Retina 4-inch 64-bit) is selected. Java Type Casting - W3Schools Can I tell police to wait and call a lawyer when served with a search warrant? // 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. 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.. with ids being an array of ints and touch being a pointer. How to use Slater Type Orbitals as a basis functions in matrix method correctly? Remarks. Based on the design of this function, which modification is right. This is why you got Error 1 C2036, from your post. Again, all of the answers above missed the point badly. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Cerror: cast to 'void *' from smaller integer type 'int' x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. A nit: in your version, the cast to void * is unnecessary. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. @Shahbaz you could but I will not suggest to a C newbie to use globals. How do I count the number of sentences in C using ". ", "? This is not even remotely "the correct answer". ../lib/odp-util.c:5489:33: note: expanded from macro 'SCAN_PUT_ATTR' Number Type Cast | Qt Forum To learn more, see our tips on writing great answers. SCAN_PUT(ATTR, NULL); I have a two functions, one that returns an int, and one that takes a const void* as an argument. void* -> integer -> void* rather than integer -> void* -> integer. windows meson: cast to 'HANDLE' (aka 'void *') from smaller integer actually no, as int my be a smaller type than a pointer ;-) But, of course with int64_t it works fine. returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size);
If you preorder a special airline meal (e.g. The correct answer is, if one does not mind losing data precision. To learn more, see our tips on writing great answers. 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 allows you to reinterpret the void * as an int. What does it mean to convert int to void* or vice versa? I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. I'm trying to learn pthreads and thing that keeps bugging me is how do i really pass argument to the function. } SCAN_END_SINGLE(ATTR) Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. 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. INT36-C. Converting a pointer to integer or integer to pointer If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. Fix for objc/45925 Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). 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. It was derived from the BCPL, and the name of the b language is possibly from the BCPL contraction. property that any valid pointer to void can be converted to this type, A missing cast in the new fast > enumeration code. 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. 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). ), Styling contours by colour and by line thickness in QGIS. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? How do I set, clear, and toggle a single bit? Now, what happens when I run it with the thread sanitizer? What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? then converted back to pointer to void, and the result will compare @DietrichEpp can you explain what is race condition with using. I don't see how anything bad can happen . 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. 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. c - Cast int to void* - Stack Overflow Once you manage to make this cast, then what?! I wish that you write those answer first than the explanation. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. this way you won't get any warning. return ((void **) returnPtr);} /* Matrix() */. 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. Have a question about this project? *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 . The main point is: a pointer has a platform dependent size. Asking for help, clarification, or responding to other answers. Then i can continue compiling. this way I convert an int to a void* which is much better than converting a void* to an int. C++ how to get the address stored in a void pointer? 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. */ >> -bool >> +enum conversion_safety >> unsafe_conversion_p (tree type, tree expr, bool . How to correctly type cast (void*)? - social.msdn.microsoft.com How do I align things in the following tabular environment? You may declare a const int variable and cast its reference to the void*. ^~~~~~~~~~~~~~~~~~~~~ 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. 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. Implementing From will result in the Into implementation but not vice-versa. clang warnings in v1.42 Issue #265 ocornut/imgui GitHub Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. 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. reinterpret_cast conversion - cppreference.com @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. (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. Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. Replacing broken pins/legs on a DIP IC package, How to handle a hobby that makes income in US. Casting type void to uint8_t - Arduino Forum What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? (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. 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. What video game is Charlie playing in Poker Face S01E07? Connect and share knowledge within a single location that is structured and easy to search. There's no proper way to cast this to int in general case. 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 . This is what the second warning is telling you. Making statements based on opinion; back them up with references or personal experience. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? ^~~~~~~~~~~~~~~~~~~~ However even though their types are different, the address is going to be the same. How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? Evaluate integer expressions in a larger size before comparing or assigning to that size.Note that (time_+t)-1 also complies with INT31-C-EX3. Implicit Type Conversion is also known as 'automatic type conversion'. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. Instead of using a long cast, you should cast to size_t. 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. casting from int to void* and back to int - C / C++ How to use Slater Type Orbitals as a basis functions in matrix method correctly? Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. C / C++ Forums on Bytes. Do new devs get fired if they can't solve a certain bug? Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). Visit Microsoft Q&A to post new questions. 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; static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. How to use Slater Type Orbitals as a basis functions in matrix method correctly? You think by casting it here that you are avoiding the problem! My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. void* to an array - C++ Forum - cplusplus.com You are right! converted back to pointer to void, and the result will compare equal It is purely a compile-time directive which instructs the compiler to treat expression as if it had . A nit: in your version, the cast to void * is unnecessary. But I'm nitpicking .. The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. Thanks for contributing an answer to Stack Overflow! What is the point of Thrower's Bandolier? 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. 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. I'm trying to create a void* from an int. Yeah, the tutorial is doing it wrong. ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). static_cast conversion - cppreference.com And in this context, it is very very very common to see programmers lazily type cast the. Mutually exclusive execution using std::atomic? SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); Type casting is when you assign a value of one primitive data type to another type. vegan) just to try it, does this inconvenience the caterers and staff?
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