If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. BUT converting a pointer to void* and back again is well supported (everywhere). 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. 472,096 Members | 2,054 Online. For example, a variable of type long (64-bit integer) can store any value that an int (32-bit integer) can store. Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? this way you won't get any warning. Referring to N1570 7.20.1.4/p1 (Integer types capable of holding object pointers): The following type designates a signed integer type with the property [Solved] Error "Cast from pointer to smaller type 'int' loses And, most of these will not even work on gcc4. What differentiates living as mere roommates from living in a marriage-like relationship? This thread has been closed and replies have been disabled. For example, the string cannot be implicitly converted to int. @ck_ I didn't realize the error in the question is actually an error by default, not a warning-turned-error. i32 -> u32) is a no-op Casting from a larger integer to a smaller integer (e.g. @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. You may declare a const int variable and cast its reference to the void*. If the data types are compatible, then Java will perform the conversion automatically known as Automatic Type Conversion, and if not then they need to be cast or converted explicitly. 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. How to find the size of an array (from a pointer pointing to the first element array)? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. C++ how to get the address stored in a void pointer? You can use any other pointer, or you can use (size_t), which is 64 bits. static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). What are the advantages of running a power tool on 240 V vs 120 V? So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Which was the first Sci-Fi story to predict obnoxious "robo calls"? Just edited. For more information, see How to safely cast using pattern matching and the as and is operators. Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. Since all pointers on 64-bit Windows are 64 bits, you are growing the data size from 32 bits backto 64 bits. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Short story about swapping bodies as a job; the person who hires the main character misuses his body. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. 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. How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? dynamic_cast safely converts pointers and references to classes up, down and sideways along the inheritance hierarchy - according to CppReference. I'm having a little bit of trouble regarding pointer casting in my program. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. Half your pointer will be garbage. @BlueMoon Thanks a lot! On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. Keep in mind that thrArg should exist till the myFcn() uses it. In the following example, the compiler implicitly converts the value of num on the right to a type long before assigning it to bigNum. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. cwindowccwindowsword[3]={"ab"};_ab charPersondebug, A, A, , "C" ???? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 4. Type Conversions - C in a Nutshell [Book] - O'Reilly Online Learning These kinds of operations are called type conversions. I would like to know the reason. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. 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 . equal to the original pointer: First you are using a define, which is not a variable. This is an old C callback mechanism so you can't change that. Not the answer you're looking for? what does it mean to convert int to void* or vice versa? property that any valid pointer to void can be converted to this type, Therefore, you need to change it to long long instead of long in windows for 64 bits. To learn more, see our tips on writing great answers. @jackdoe: It's a waste of human life to write code that "you may need in the future". I think the solution 3> should be the correct one. Canadian of Polish descent travel to Poland with Canadian passport. casting from int to void* and back to int. Why don't we use the 7805 for car phone chargers? does lazarbeam have a wife; Books. How to correctly type cast (void*)? - social.msdn.microsoft.com If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. Does it effect my blogs SEO rankings? 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). 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. How to correctly cast a pointer to int in a 64-bit application? 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. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. Connect and share knowledge within a single location that is structured and easy to search. No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. 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". cast to void *' from smaller integer type 'int cast to void *' from smaller integer type 'int. Is "I didn't think it was serious" usually a good defence against "duty to rescue"? Disabling "cast from pointer to smaller type uint32_t" error in Clang You might want to typedef, You should change your code to handle this. Casting between types - The Rust Programming Language LettuceConnectionFactory was destroyed and cannot be used - CSDN How a top-ranked engineering school reimagined CS curriculum (Ep. Clang warnings for an invalid casting? - The FreeBSD Forums Most answers just try to extract 32 useless bits out of the argument. what does it mean to convert int to void* or vice versa? Folder's list view has different sized fonts in different folders. If your standard library (even if it is not C99) happens to provide these types - use them. Solution 1. I can easily imagine a situation where rewriting code using, Disabling "cast from pointer to smaller type uint32_t" error in Clang, https://github.com/llvm-mirror/clang/blob/release_50/include/clang/Basic/DiagnosticSemaKinds.td#L6193, https://github.com/llvm-mirror/clang/blob/release_50/lib/Sema/SemaCast.cpp#L2112, How a top-ranked engineering school reimagined CS curriculum (Ep. In C#, you can perform the following kinds of conversions: Implicit conversions: No special syntax is required because the conversion always succeeds and no data will be lost. 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. If this is the data to a thread procedure, then you quite commonly want to pass by value. 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. I'm new to coding and am trying to implement a simple program on my own, that prompts the user the number of residents in an apt complex, the prompts the user to enter the names and apt numbers of each resident. (i.e. Connect and share knowledge within a single location that is structured and easy to search. 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. converted back to pointer to void, and the result will compare equal 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! 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;. Find centralized, trusted content and collaborate around the technologies you use most. If the function had the correct signature you would not need to cast it explicitly. When do you use in the accusative case? @Martin York: No, it doesn't depend on endiannness. But to just truncate the integer value and not having to fix all the wrong uses of uint32_t just yet, you could use static_cast(reinterpret_cast(ptr)). There is no "correct" way to store a 64-bit pointer in an 32-bit integer. pcs leave before deros; chris banchero brother; tc dimension custom barrels; cast void pointer to char array. Again, all of the answers above missed the point badly. 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. Can I use my Coinbase address to receive bitcoin? drivers/gpu/drm/mediatek/mtk_disp_ovl_adaptor.c:415:10: warning: cast 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). It does not because. 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. So,solution #3 works just fine. I cannot reverse my upvote of user384706's answer, but it's wrong. 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. Use #include to define it. this way I convert an int to a void* which is much better than converting a void* to an int. On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. Should I re-do this cinched PEX connection? u8 -> u32) will zero-extend if the source is unsigned sign-extend if the source is signed Did the drapes in old theatres actually say "ASBESTOS" on them? This is not a conversion at all. Cerror: cast to 'void *' from smaller integer type 'int (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. Using an integer address (like &x) is probably wrong, indeed each modification you will execute on x will affect the pass behaviour. 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. Embedded hyperlinks in a thesis or research paper. a cast of which the programmer should be aware of what (s)he is doing. Which reverse polarity protection is better and why? pointer/reference to a derived class pointer/reference. @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? ", "? Say you hack this successfully. They should do their job unless your code is too tricky. how about using uintptr_t, most of your pointer arithmetic may still works. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. I don't see how anything bad can happen . Thanks for contributing an answer to Stack Overflow! By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. This allows you to reinterpret the void * as an int. Asking for help, clarification, or responding to other answers. Or keep using a C cast even when C++ code compiled as C++. What is this brick with a round back and a stud on the side used for? Thanks for contributing an answer to Stack Overflow! He also rips off an arm to use as a sword. What does 'They're at four. When is casting void pointer needed in C? My blogs h2 and other tags are in these manner. "I think what you should do is actually pass the address of the variable to the function" Not necessarily. This option of Python is missing in matplotlibcpp within Visual Studio -> works only in b/w ! Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, Setting a buffer of char* with intermediate casting to int*. You think by casting it here that you are avoiding the problem! How to cast a void pointer to any other type in C || #C Programming language || Coding is Life 487 03 : 37 Unable to cast object of type 'System DateTime' to type 'System String' SharpCoder 336 10 : 53 Tkinter window geometry to manage height width and zoom out using state and resizable () option plus2net 107 Author by david.brazdil @DavidHeffernan I rephrased that sentence a little. MIP Model with relaxed integer constraints takes longer to solve than normal model, why? there How should an excellent flowchart be drawn? If your standard library (even if it is not C99) happens to provide these types - use them. Which was the first Sci-Fi story to predict obnoxious "robo calls"? " is pointer to interface, not interface" confusion, Cast from uint8_t pointer to uint32_t integer compilation error. You can then disable this diagnostic completely by adding -Wno-extra-tokens (again, the "extra tokens" warning is an example), or turn it into a non-fatal warning by means of -Wno-error=extra-tokens. Why don't we use the 7805 for car phone chargers? The most general answer is - in no way. It is safer to not make assumptions, but rather check the type. error: cast from 'void*' to 'int' loses precision - Stack Overflow [-Wextra-tokens] (if it doesn't, remove the -fno-diagnostics-show-option flag). Find centralized, trusted content and collaborate around the technologies you use most. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" i You use the address-of operator & to do that. Can I use the spell Immovable Object to create a castle which floats above the clouds? Explanation Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility . ', referring to the nuclear power plant in Ignalina, mean? Not the answer you're looking for? 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 flat out wrong. Once you manage to make this cast, then what?! I think that's what you want: // Declaration uint8_t *myData; void loop () { myData = "custom string"; } Find centralized, trusted content and collaborate around the technologies you use most. The following program casts a double to an int. last post by: I'm looking for the name of the following casting style in order to do 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. Thanks for contributing an answer to Stack Overflow! Wrong. What is the difference between const int*, const int * const, and int const *? (void *)(long)i, Copyright 2011-2023 SegmentFault. But this code pass the normal variable .. You use the address-of operator & to do that int x = 10; void *pointer = &x; And in the function you get the value of the pointer by using the dereference operator *: int y = * ( (int *) pointer); Share Improve this answer Follow edited Apr 15, 2013 at 13:58 answered Apr 15, 2013 at 13:53 Some programmer dude 396k 35 399 609 1 Why did US v. Assange skip the court of appeal? # * # (intptr_t) # # warning: cast to pointer from integer of different size # (intptr_t)IDE # (void*) . Please help me with the right way to convert void* to int in c++ Mar 30, 2020 at 10:44am George P (5286) Maybe try reinterpret_cast? Why does flowing off the end of a non-void function without returning a value not produce a compiler error? Connect and share knowledge within a single location that is structured and easy to search. Interpreting non-statistically significant results: Do we have "no evidence" or "insufficient evidence" to reject the null? It's an int type guaranteed to be big enough to contain a pointer. pthread create managing values generated in function (in c), Establishing TCP socket connection between PHP client and C server on Ubuntu. Examples include conversions from smaller to larger integral types, and conversions from derived classes to base classes. u32 -> u8) will truncate Casting from a smaller integer to a larger integer (e.g. Integer conversions, both implicit and explicit (using a cast), must be guaranteed not to result in lost or misinterpreted data. some reading around on it and why it is sometimes used. 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). 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; I am using the UDF of the Ansys Manual Book as a base for what I intended, but I am trying to incorporate a second component to my condensable mixture, being methanol . Can my creature spell be countered if I cast a split second spell after it? Unfortunately, that hardware is 64-bit and the code contains many instances of pointer arithmetic that expects pointers to be 32-bit, i.e. So make sure you understand what you are doing! Connect and share knowledge within a single location that is structured and easy to search. c printf() C , {} . Offline ImPer Westermark over 12 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. or, Array with multiple data types? What I am saying is that it would be safer to use new(5) rather than 5 and deal with it appropriately at the other end. Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? The semantics of numeric casts are: Casting between two integers of the same size (e.g. 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. A good thing in general, but if you want to disable the warning, just do it. How to convert a factor to integer\numeric without loss of information? Two MacBook Pro with same model number (A1286) but different year. This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s). Pros: The problem with C casts is the ambiguity of the operation; sometimes you are doing a conversion (e.g., (int)3.5) and sometimes you are doing a cast (e.g., (int)"hello"); C++ casts avoid this. Run this code to find how Java handles division and what casting can do to the results. Type conversion in Java with Examples - GeeksforGeeks Boolean algebra of the lattice of subspaces of a vector space? Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. Without RTTI your code will be cleaner | Sandor Dargo's Blog The only. But then you need to cast your arguments inside your thread function which is quite unsafe cf. Casting is required when information might be lost in the conversion, or when the conversion might not succeed for other reasons. Basically its a better version of (void *)i. Since gcc compiles that you are performing arithmetic between void* and an int (1024). To avoid truncating your pointer, cast it to a type of identical size. that any valid pointer to void can be converted to this type, then Please tell me error: cast from 'void*' to 'int' loses precision, How a top-ranked engineering school reimagined CS curriculum (Ep. Not the answer you're looking for? it often does reinterpret_cast(ptr). c - Cast int to void* - Stack Overflow Is pthread_join a must when using pthread in linux? Is it safe to publish research papers in cooperation with Russian academics? It keeps throwing this exact error message even though both types are 32 bits wide. You could use this code, and it would do the same thing as casting ptr to (char*). The preprocessor will replace your code by this: This is unlikely what you are trying to do. So you know you can cast it back like this. But to answer your question: No, you can't disable it, though you can work around it. And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. He also rips off an arm to use as a sword, Two MacBook Pro with same model number (A1286) but different year. So reinterpret_cast has casted it to long type and then static_cast safely casts long to int, if you are ready do truncte the data. Then he wants to convert px to Hello, He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. The problem is not with casting, but with the target type loosing half of the pointer. How a top-ranked engineering school reimagined CS curriculum (Ep. For more information, see User-defined conversion operators. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. What does casting to void* does when passing arguments to variadic functions? 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. @Shahbaz you could but I will not suggest to a C newbie to use globals. I saw on a couple of recent posts people saying that casting the return How to Cast a void* ponter to a char without a warning? [Solved] Disabling "cast from pointer to smaller type | 9to5Answer If we had a video livestream of a clock being sent to Mars, what would we see? (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 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. Convert integers, floating-point values and enum types to enum types. Interpreting non-statistically significant results: Do we have "no evidence" or "insufficient evidence" to reject the null? Is a downhill scooter lighter than a downhill MTB with same performance? You are right! linux c-pthreads: problem with local variables. 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. 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. This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). void* -> integer -> void* rather than integer -> void* -> integer. For example, assigning an int value to a long variable. comment:4 by Kurt Schwehr, 8 years ago r28216 removes OGDIDataset:: GetInternalHandle from trunk Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. For more information, see How to convert a byte array to an int, How to convert a string to a number, and How to convert between hexadecimal strings and numeric types. Why did US v. Assange skip the court of appeal? 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. Making statements based on opinion; back them up with references or personal experience. To avoid truncating your pointer, cast it to a type of identical size. I had this error while trying to cross compile the header from libstdc++ 5.4.0 with clang 7.0.1 for ARM. As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). For a complete list of all implicit numeric conversions, see the Implicit numeric conversions section of the Built-in numeric conversions article. How can I control PNP and NPN transistors together from one pin? replace uint32_t by uintptr_t wholesale, then fix remaining cases one by one.

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