error: request for member '..' in '..' which is of non-class type. 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. Offline ImPer Westermark over 12 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. Why are players required to record the moves in World Championship Classical games? When is casting void pointer needed in C? replace uint32_t by uintptr_t wholesale, then fix remaining cases one by one. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Is pthread_join a must when using pthread in linux? a cast of which the programmer should be aware of what (s)he is doing. 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). Explanation Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility . While working with Threads in C, I'm facing the warning, "warning: cast to pointer from integer of different size". 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. Yeah, the tutorial is doing it wrong. Not the answer you're looking for? 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. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. 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. it often does reinterpret_cast<uint32_t> (ptr). what does it mean to convert int to void* or vice versa? BUT converting a pointer to void* and back again is well supported (everywhere). 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. So you know you can cast it back like this. In this case, casting the pointer back to an integer is meaningless, because . To learn more, see our tips on writing great answers. Which was the first Sci-Fi story to predict obnoxious "robo calls"? If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. 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! Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Embedded hyperlinks in a thesis or research paper. 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. (void *)i Error: cast to 'void *' from smaller integer type 'int', PS: UBUNTUCLANG3.5 clang -O0 -std=gnu11 -march=native -lm -lpthread pagerank.c -o pagerank, , i It is safer to not make assumptions, but rather check the type. There are two occurences in "SemaCast.cpp" -- one of which suggests it's sensitive to MS extensions, https://github.com/llvm-mirror/clang/blob/release_50/lib/Sema/SemaCast.cpp#L2112 However, you are also casting the result of this operation to (void*). Thus as a result it may be less error prone to generate a pointer dynamcially and use that. Canadian of Polish descent travel to Poland with Canadian passport. I would like to know the reason. This is flat out wrong. 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. Please start a new discussion. Connect and share knowledge within a single location that is structured and easy to search. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? Converting a void* to an int is non-portable way that may work or may not! You can use any other pointer, or you can use (size_t), which is 64 bits. If the result lies outside the range of representable values by the type, the conversion causes, Otherwise, if the conversion is between numeric types of the same kind (integer-to-integer or floating-to-floating), the conversion is valid, but the value is. I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. It keeps throwing this exact error message even though both types are 32 bits wide. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. Why did US v. Assange skip the court of appeal? 472,096 Members | 2,054 Online. last post by: I'm looking for the name of the following casting style in order to do MIP Model with relaxed integer constraints takes longer to solve than normal model, why? Say I want to make But to answer your question: No, you can't disable it, though you can work around it. some reading around on it and why it is sometimes used. rev2023.5.1.43405. The best way is, if one can, do not do such casting, instead, if the same memory address has to be shared for pointer and int (e.g. What does it mean to convert int to void* or vice versa? The proper way is to cast it to another pointer type. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. Your strategy will not work for stack-allocated objects, be careful!! A boy can regenerate, so demons eat him for years. A good thing in general, but if you want to disable the warning, just do it. To avoid truncating your pointer, cast it to a type of identical size. Expressions Converts between types using a combination of implicit and user-defined conversions. 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. Can I use my Coinbase address to receive bitcoin? Is there a way to disable it? Again, all of the answers above missed the point badly. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. I am looking to clean up the Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? 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. 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. -1, Uggh. (void *)i Error: cast to 'void *' from smaller integer type 'int' PS: UBUNTUCLANG3.5 clang -O0 -std=gnu11 -march=native -lm -lpthread pagerank.c -o pagerank c pthreads 4 10.8k 2 21 2015-06-05 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;. Therefore, after you declare i as an int, you cannot assign the string "Hello" to it, as the following code shows: However, you might sometimes need to copy a value into a variable or method parameter of another type. I was sent this code and can't figure out why I keep getting "Incomplete Data type Error, Embracing Modern Android Development: A Dive into Java and Kotlin. You think by casting it here that you are avoiding the problem! what does it mean to convert int to void* or vice versa? Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" From: Hans de Goede <hdegoede@redhat.com> To: Mark Gross <mgross@linux.intel.com> Cc: Hans de Goede <hdegoede@redhat.com>, Andy Shevchenko <andy@infradead.org>, platform-driver-x86@vger.kernel.org, kernel test robot <lkp@intel.com> Subject: [PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type warning Date: Mon, 23 Jan 2023 14:28:24 +0100 [thread overview] Message-ID: <20230123132824. . I agree that you should bite the bullet and fix the code to use the correct integer type. The preprocessor will replace your code by this: This is unlikely what you are trying to do. The following program casts a double to an int. 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. However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. For more information, see the Conversions section of the C# language specification. 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). That's not a good idea if the original object (that was cast to void*) was an integer. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. Asking for help, clarification, or responding to other answers. error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. To learn more, see our tips on writing great answers. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. Don't do that. " is pointer to interface, not interface" confusion, Cast from uint8_t pointer to uint32_t integer compilation error. @jackdoe: It's a waste of human life to write code that "you may need in the future". Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). void *ptr; int n = (int)ptr; So in c++ i tried below int n = atoi (static_cast<const char*> (ptr)); This crashes when i run. How to set, clear, and toggle a single bit? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. What you do here is undefined behavior, and undefined behavior of very practical sort. rev2023.5.1.43405. One could try -fms-extensions (hopefully not -fms-compatibility), but that would bring all the shebang with it. It's an int type guaranteed to be big enough to contain a pointer. Most answers just try to extract 32 useless bits out of the argument. is returned by the malloc. cwindowccwindowsword[3]={"ab"};_ab charPersondebug, A, A, , "C" ???? This is what the second warning is telling you. Which ability is most related to insanity: Wisdom, Charisma, Constitution, or Intelligence? Did the drapes in old theatres actually say "ASBESTOS" on them? 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. Asking for help, clarification, or responding to other answers. 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. So instead I modified the implementation of malloc to ensure it never allocates memory above the 4GB limit. It's not them. Join Bytes to post your question to a community of 472,246 software developers and data experts. Were sorry. I have a question about casting a function pointer. For example, assigning an int value to a long variable. 1) zero or one conversion from the following set: lvalue-to-rvalue conversion, array-to-pointer conversion, and function-to-pointer conversion; 2) zero or one numeric promotion or numeric conversion; 3) zero or one function pointer conversion; (since C++17) 4) zero or one qualification conversion. You are right! Yes, for the reason you mentioned that's the proper intermediate type. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. This allows you to reinterpret the void * as an int. Can anybody explain how to pass an integer to a function which receives (void * ) as a parameter? Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. There's no proper way to cast this to int in general case. How can I control PNP and NPN transistors together from one pin? In the realm of Android development, two languages have consistently stood out: Java and Kotlin. What would you do next year when you need to port it to yet another experimental hardware? Thanks in A colleague asked me something along the lines of the following today. If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. pthread create managing values generated in function (in c), Establishing TCP socket connection between PHP client and C server on Ubuntu. then converted back to pointer to void, and the result will compare For more information, see Polymorphism. More info about Internet Explorer and Microsoft Edge, How to convert between hexadecimal strings and numeric types, How to safely cast using pattern matching and the as and is operators. Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. Put your define inside a bracket: without a problem. Two MacBook Pro with same model number (A1286) but different year. Becase one can always legally cast any Hello, What were the most popular text editors for MS-DOS in the 1980s? Thanks for contributing an answer to Stack Overflow! pointer/reference to a derived class pointer/reference. Was Aristarchus the first to propose heliocentrism? And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. comment:4 by Kurt Schwehr, 8 years ago r28216 removes OGDIDataset:: GetInternalHandle from trunk I need to execute a SQL Server stored procedure from Java/Spring, and the SP has a try/catch block that logs errors to a table. 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]. @Xax: Here's a fixed version, without the race condition: gist.github.com/depp/241d6f839b799042c409, gist.github.com/depp/3f04508a88a114734195, How a top-ranked engineering school reimagined CS curriculum (Ep. Casting arguments inside the function is a lot safer. For a complete list of supported explicit numeric conversions, see the Explicit numeric conversions section of the Built-in numeric conversions article. Since gcc compiles that you are performing arithmetic between void* and an int (1024). rev2023.5.1.43405.