The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. I'm working on a school project that involves porting a large piece of C++ code on an experimental piece of hardware. How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. pointer/reference to a derived class pointer/reference. You are right! But gcc always give me a warning, that i cannot cast an int to a void*. 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;. Why did US v. Assange skip the court of appeal? You can use any other pointer, or you can use (size_t), which is 64 bits. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. linux c-pthreads: problem with local variables. It keeps throwing this exact error message even though both types are 32 bits wide. By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use. Thank you all for your feedback. MIP Model with relaxed integer constraints takes longer to solve than normal model, why? reinterpret_cast<void *>(42)). 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. Both languages have been widely adopted by How to plot text in color? So you know you can cast it back like this. Did the drapes in old theatres actually say "ASBESTOS" on them? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. You might want to typedef, You should change your code to handle this. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, xcode build error: Semantic issue cast from pointer to smaller type 'int' loses information. What is the symbol (which looks similar to an equals sign) called? 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. So make sure you understand what you are doing! To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? Which reverse polarity protection is better and why? 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. The most general answer is - in no way. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. I had this error while trying to cross compile the header from libstdc++ 5.4.0 with clang 7.0.1 for ARM. This is a fine way to pass integers to new pthreads, if that is what you need. The error message mentions the diagnostic responsible for error message, e.g. These kinds of operations are called type conversions. 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. Can anybody explain how to pass an integer to a function which receives (void * ) as a parameter? Should I re-do this cinched PEX connection? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. is returned by the malloc. Does it effect my blogs SEO rankings? For a complete list of supported explicit numeric conversions, see the Explicit numeric conversions section of the Built-in numeric conversions article. 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. 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. But this code pass the normal variable .. Can my creature spell be countered if I cast a split second spell after it? It's not them. Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. how to cascade 2d int array to 2d void pointer array? Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? BUT converting a pointer to void* and back again is well supported (everywhere). How to convert a factor to integer\numeric without loss of information? this way you won't get any warning. d=(double *) Hi, @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. How can I control PNP and NPN transistors together from one pin? 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". 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. Explanation Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility . Making statements based on opinion; back them up with references or personal experience. In the realm of Android development, two languages have consistently stood out: Java and Kotlin. How do I check if a string represents a number (float or int)? Interpreting non-statistically significant results: Do we have "no evidence" or "insufficient evidence" to reject the null? User without create permission can create a custom object from Managed package using Custom Rest API. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. Making statements based on opinion; back them up with references or personal experience. casting from int to void* and back to 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 . Infact I know several systems where that does not hold. As a result, it is possible to silently convert from one pointer type to another without the compiler diagnosing the problem by storing or casting a pointer to void * and then storing or casting it to the final type. A good thing in general, but if you want to disable the warning, just do it. Short story about swapping bodies as a job; the person who hires the main character misuses his body. Therefore, you need to change it to long long instead of long in windows for 64 bits. Youll be auto redirected in 1 second. pthread passes the argument as a void*. While working with Threads in C, I'm facing the warning, "warning: cast to pointer from integer of different size". So instead I modified the implementation of malloc to ensure it never allocates memory above the 4GB limit. Becase one can always legally cast any Hello, Save this piece of code as mycast.hpp and add -include mycast.hpp to your Makefile. Technically, these casts should therefore be valid. Run this code to find how Java handles division and what casting can do to the results. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. @Shahbaz you could but I will not suggest to a C newbie to use globals. Explicit conversions (casts): Explicit conversions require a cast expression. Is a downhill scooter lighter than a downhill MTB with same performance? 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; a generic module (say some ADT implementation) that requires a by: William S Fulton | rev2023.5.1.43405. Can I use my Coinbase address to receive bitcoin? "jacob navia" wrote: This question has probably been asked a million time, but here it comes The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. Visit Microsoft Q&A to post new questions. Folder's list view has different sized fonts in different folders. 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. 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. Is "I didn't think it was serious" usually a good defence against "duty to rescue"? "Signpost" puzzle from Tatham's collection. When do you use in the accusative case? 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. 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. To avoid truncating your pointer, cast it to a type of identical size. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. The following program casts a double to an int. To learn more, see our tips on writing great answers. Storage management is an important module of database, which can be subdivided into memory management and external memory management. When is casting void pointer needed in C? 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 He also rips off an arm to use as a sword. 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. What is the correct method to cast an int to a void*? It is possible for a cast operation that compiles correctly to fail at run time. This rule is particularly true for integer values that originate from untrusted sources and are used in any of the following ways: Integer operands of any pointer arithmetic, including array indexing To learn more, see our tips on writing great answers. 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. I hit this same problem in a project without C++11, and worked around it like this: Thanks for contributing an answer to Stack Overflow! For a complete list of all implicit numeric conversions, see the Implicit numeric conversions section of the Built-in numeric conversions article. 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. As shown in the following example, a type cast that fails at run time will cause an InvalidCastException to be thrown. Making statements based on opinion; back them up with references or personal experience. Use returnPtr[j] = (void *) ((long)ptr + i); ). Not the answer you're looking for? 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. 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. I saw on a couple of recent posts people saying that casting the return There is no "correct" way to store a 64-bit pointer in an 32-bit integer. Which was the first Sci-Fi story to predict obnoxious "robo calls"? 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. . Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. cwindowccwindowsword[3]={"ab"};_ab charPersondebug, A, A, , "C" ???? Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. Wrong. What were the most popular text editors for MS-DOS in the 1980s? Definition: C++ introduced a different cast system from C that distinguishes the types of cast operations. User-defined conversions: User-defined conversions are performed by special methods that you can define to enable explicit and implicit conversions between custom types that do not have a base classderived class relationship. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. Connect and share knowledge within a single location that is structured and easy to search. there How should an excellent flowchart be drawn? 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. eg. Why does setupterm terminate the program? Casting a pointer to void* and back is valid use of reinterpret_cast<>. Find centralized, trusted content and collaborate around the technologies you use most. What you do here is undefined behavior, and undefined behavior of very practical sort. How do I force make/GCC to show me the commands? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. again. C# provides the is operator to enable you to test for compatibility before actually performing a cast. does lazarbeam have a wife; Books. You can use any other pointer, or you can use (size_t), which is 64 bits. how about using uintptr_t, most of your pointer arithmetic may still works. What differentiates living as mere roommates from living in a marriage-like relationship? @ck_ I didn't realize the error in the question is actually an error by default, not a warning-turned-error. The following program casts a double to an int. However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. 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. The only. 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 rev2023.5.1.43405. There's no proper way to cast this to int in general case. Not the answer you're looking for? I agree that you should bite the bullet and fix the code to use the correct integer type. Asking for help, clarification, or responding to other answers. it often does reinterpret_cast(ptr). Connect and share knowledge within a single location that is structured and easy to search. converted back to pointer to void, and the result will compare equal u32 -> u8) will truncate Casting from a smaller integer to a larger integer (e.g. Say I want to make Which ability is most related to insanity: Wisdom, Charisma, Constitution, or Intelligence? (void *)(long)i, Copyright 2011-2023 SegmentFault. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). ", "!"? Again, all of the answers above missed the point badly. The preprocessor will replace your code by this: This is unlikely what you are trying to do. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. For more information, see the Conversions section of the C# language specification. Solution 1. rev2023.5.1.43405. Implementation-dependent. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). pcs leave before deros; chris banchero brother; tc dimension custom barrels; cast void pointer to char array. Passing negative parameters to a wolframscript, Generating points along line with specifying the origin of point generation in QGIS. For example, (double) 1/3 will give a double result instead of an int one. Asking for help, clarification, or responding to other answers. Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? The C Standard allows any object pointer to be cast to and from void *. For example, a variable of type long (64-bit integer) can store any value that an int (32-bit integer) can store. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Thanks for contributing an answer to Stack Overflow! (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 # * # (intptr_t) # # warning: cast to pointer from integer of different size # (intptr_t)IDE # (void*) . What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. And in this context, it is very very very common to see programmers lazily type cast the. 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. Many errors come from warnings. In C (int)b is called an explicit conversion, i.e. Typical examples include numeric conversion to a type that has less precision or a smaller range, and conversion of a base-class instance to a derived class. 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"? If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. 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? To learn more, see our tips on writing great answers. this way you won't get any warning. Syntax static_cast< new-type > ( expression ) Returns a value of type new-type . Why don't we use the 7805 for car phone chargers? 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). . Or, they are all wrong. this way I convert an int to a void* which is much better than converting a void* to an int. I would create a structure and pass that as void* to pthread_create. ), For those who are interested. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. But then you need to cast your arguments inside your thread function which is quite unsafe cf. What are the advantages of running a power tool on 240 V vs 120 V? u8 -> u32) will zero-extend if the source is unsigned sign-extend if the source is signed This allows you to reinterpret the void * as an int. 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. last post by: I'm looking for the name of the following casting style in order to do You need to pass an actual pointer. Question is, how do I explain this to Clang? Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, error: cast from void* to int loses precision, cast to pointer from integer of different size, pthread code. comment:4 by Kurt Schwehr, 8 years ago r28216 removes OGDIDataset:: GetInternalHandle from trunk How to cast/convert pointer to reference in C++, clang error: unknown argument: '-mno-fused-madd' (python package installation failure). How to set, clear, and toggle a single bit? MIP Model with relaxed integer constraints takes longer to solve than normal model, why? Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. It is safer to not make assumptions, but rather check the type. Thanks for pointing that out. Write values of different data types in sequence in memory? Hello, I am currently working on a UDF for the heterogeneous reaction using it to describe a simple equilibrium model using the Antoine equation and vapor pressure. Why did DOS-based Windows require HIMEM.SYS to boot? MIP Model with relaxed integer constraints takes longer to solve than normal model, why? Was Aristarchus the first to propose heliocentrism? long guarantees a pointer size on Linux on any machine. 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). No special syntax is necessary because a derived class always contains all the members of a base class. How create a simple program using threads in C? Now, what happens when I run it with the thread sanitizer? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Say you hack this successfully. Why are players required to record the moves in World Championship Classical games? Most answers just try to extract 32 useless bits out of the argument. Mar 30, 2020 at 11:12am Generating points along line with specifying the origin of point generation in QGIS. Two MacBook Pro with same model number (A1286) but different year. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. value of malloc is bad, like: Can I use the spell Immovable Object to create a castle which floats above the clouds? In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. If the function had the correct signature you would not need to cast it explicitly. Thanks in A colleague asked me something along the lines of the following today. The -fms-extensions flag resolved the issue. Casting is required when information might be lost in the conversion, or when the conversion might not succeed for other reasons. I don't understand why the following two cases produce different Hi, I've this question: suppose we have two differently typed pointers: @jackdoe: It's a waste of human life to write code that "you may need in the future". for (i=0, j=0; j

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