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. What is "cast from integer to pointer of different size" warning? If the function had the correct signature you would not need to cast it explicitly. " is pointer to interface, not interface" confusion, Cast from uint8_t pointer to uint32_t integer compilation error. Can I use an 11 watt LED bulb in a lamp rated for 8.6 watts maximum? this way you won't get any warning. For some type X he has: dynamic_cast safely converts pointers and references to classes up, down and sideways along the inheritance hierarchy - according to CppReference. Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. What is this brick with a round back and a stud on the side used for. Is "I didn't think it was serious" usually a good defence against "duty to rescue"? to the original pointer: The following type designates an unsigned integer type with the Once you manage to make this cast, then what?! [PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type 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. for saving RAM), use union, and make sure, if the mem address is treated as an int only if you know it was last set as an int. LLNL's tutorial is bad and they should feel bad. Asking for help, clarification, or responding to other answers. MIP Model with relaxed integer constraints takes longer to solve than normal model, why? If the types are from the same inheritance tree, then you should either use dynamic_casts or even better, you should benefit from dynamic dispatching.. dynamic_cast is slightly better, but still should be avoided. char **array; This is a fine way to pass integers to new pthreads, if that is what you need. Connect and share knowledge within a single location that is structured and easy to search. It is commonly called a pointer to T and its type is T*. 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;. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. This code is a bit odd (but a void* can certainly host a int on all architectures on which GDAL can be compiled), and certainly unused by anyone, so you could just remove the GetInternalHandle () implementation as well if you prefer. Terrible solution. ', referring to the nuclear power plant in Ignalina, mean? 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. Did the drapes in old theatres actually say "ASBESTOS" on them? Not the answer you're looking for? I think that's what you want: // Declaration uint8_t *myData; void loop () { myData = "custom string"; } If you are planning to use pthreads and you are planning to pass the pass function to pthread_create, you have to malloc/free the arguments you are planning to use (even if the threaded function just need a single int). Casting int to void* : r/C_Programming - Reddit Types - D Programming Language By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use. For example, if the pointers in a system are stored in 16 bits, but integers are stored in 8 bits, a total of 8 bits would be lost in the . And in the function you get the value of the pointer by using the dereference operator *: Please read why glib provide macros for this kind of conversions, there's no need to repeat the text here. Use returnPtr[j] = (void *) ((long)ptr + i); ). Why did US v. Assange skip the court of appeal? 1.6. Casting and Ranges of Variables AP CSAwesome Why don't we use the 7805 for car phone chargers? What is this brick with a round back and a stud on the side used for? The correct answer is, if one does not mind losing data precision. Since the culprit is probably something like -Wall which enables many warnings you should keep on, you should selectively disable this single warning. If the sizes are different then endianess comes into play. Find centralized, trusted content and collaborate around the technologies you use most. There is no "correct" way to store a 64-bit pointer in an 32-bit integer. Thanks for contributing an answer to Stack Overflow! Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? 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. Why did US v. Assange skip the court of appeal? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. rev2023.5.1.43405. 4. Type Conversions - C in a Nutshell [Book] - O'Reilly Online Learning As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. Convert integers, floating-point values and enum types to enum types. Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? Connect and share knowledge within a single location that is structured and easy to search. reinterpret_cast<void *>(42)). Why does Acts not mention the deaths of Peter and Paul? 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. Could a subterranean river or aquifer generate enough continuous momentum to power a waterwheel for the purpose of producing electricity? Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. For a complete list of all implicit numeric conversions, see the Implicit numeric conversions section of the Built-in numeric conversions article. INT31-C. Ensure that integer conversions do not result in lost or Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. #5779 (cast to 'void *' from smaller integer type 'int') - GDAL value of malloc is bad, like: This is why you got Error 1 C2036, from your post. And in this context, it is very very very common to see programmers lazily type cast the. (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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Going through them one by one would be very tedious and since this is an experimental project anyway, I'm happy to settle for a "hackish" workaround. Put your define inside a bracket: #define M_TABLE_SIZE (64*1024) Now, you can do: static const void* M_OFFSET = (void*) M_TABLE_SIZE; without a problem. 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. It seems both static_cast and dynamic_cast can cast a base class Mar 30, 2020 at 11:12am The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. @jackdoe: It's a waste of human life to write code that "you may need in the future". Is a downhill scooter lighter than a downhill MTB with same performance? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. #, In a 64 bit machine with sizeof(int) == 4. Which ability is most related to insanity: Wisdom, Charisma, Constitution, or Intelligence? 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. However, if a conversion cannot be made without a risk of losing information, the compiler requires that you perform an explicit conversion, which is called a cast. I am running into the same problem where I am using Clang's static analyzer and clang-tidy to scan code on a 64-bit system that is targeted for a 32-bit system. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. dynamic, and reinterpret casting. BUT converting a pointer to void* and back again is well supported (everywhere). Making statements based on opinion; back them up with references or personal experience. rev2023.5.1.43405. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. 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; Explicitly call a single-argument constructor or a conversion operator. For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. How to find the size of an array (from a pointer pointing to the first element array)? [-Wextra-tokens] (if it doesn't, remove the -fno-diagnostics-show-option flag). The next Access Europe Meeting is on Wed 3 May 2023. Just because you're altering. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. 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. 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" (. 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. What is the symbol (which looks similar to an equals sign) called? You can use any other pointer, or you can use (size_t), which is 64 bits. Folder's list view has different sized fonts in different folders. Using printf with a pointer to float gives an error, Meaning of int (*) (int *) = 5 (or any integer value), Casting int to void* loses precision, and what is the solution in required cases, Short story about swapping bodies as a job; the person who hires the main character misuses his body. For example, the string cannot be implicitly converted to int. For more information, see How to safely cast using pattern matching and the as and is operators. You might want to typedef, You should change your code to handle this. Visit Microsoft Q&A to post new questions. Asking for help, clarification, or responding to other answers. static_cast conversion - cppreference.com Can I use the spell Immovable Object to create a castle which floats above the clouds? The casting operators (int) and (double) are used right next to a number or variable to create a temporary value converted to a different data type. Thanks for contributing an answer to Stack Overflow! Thanks for contributing an answer to Stack Overflow! Run this code to find how Java handles division and what casting can do to the results. static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). When do you use in the accusative case? [Solved] Properly casting a `void*` to an integer in C++ However, this specific error is not due to a warning and I can't find any option to disable errors (makes sense, since most errors are fatal). Expressions Converts between types using a combination of implicit and user-defined conversions. If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. Posted on Author Author c - How to cast an integer to void pointer? - Stack Overflow The error message mentions the diagnostic responsible for error message, e.g. What you do here is undefined behavior, and undefined behavior of very practical sort. The program will not compile without the cast. I saw on a couple of recent posts people saying that casting the return how about using uintptr_t, most of your pointer arithmetic may still works. i -1, Uggh. Does a password policy with a restriction of repeated characters increase security? How to convert a factor to integer\numeric without loss of information? But then you need to cast your arguments inside your thread function which is quite unsafe cf. Asking for help, clarification, or responding to other answers. 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. Canadian of Polish descent travel to Poland with Canadian passport. 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. You are right! 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. pthread passes the argument as a void*. What are the advantages of running a power tool on 240 V vs 120 V? again. replace uint32_t by uintptr_t wholesale, then fix remaining cases one by one. For example, assigning an int value to a long variable. [Solved] Error "Cast from pointer to smaller type 'int' loses I agree passing a dynamically allocated pointer is fine (and I think the best way). /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. Wrong. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. I want to learn the difference between the three type cast operators: Hi, This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). 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. pthread create managing values generated in function (in c), Establishing TCP socket connection between PHP client and C server on Ubuntu. Why did DOS-based Windows require HIMEM.SYS to boot?
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