For example, the main thread could wait for all of the other threads to end before terminating. 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. returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size);
[that could be a TODO - not to delay solving the ICE]. Maybe you can try this too. *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 . 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. Converts between types using a combination of implicit and user-defined conversions. Based on the design of this function, which modification is right. How to notate a grace note at the start of a bar with lilypond? Not the answer you're looking for? What is the difference between const int*, const int * const, and int const *? This is an old C callback mechanism so you can't change that. RNINGS" "-D_CRT_SECURE_NO_DEPRECATE" -MD -MQ lib/libopenvswitch.a.p/odp-util.c.obj -MF "lib\libopenvswitch.a.p\odp-util.c.obj.d" -o lib/libopenvswitch.a.p/od Disconnect between goals and daily tasksIs it me, or the industry? whether it was an actual problem is a different matter though. How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. The program can be set in such a way to ask the user to inform the type of data and . 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 using cocos2d-x-2.2.2. It solved my problem too. And when assigning to a void pointer, all type information is lost. It is easier to understand and write than any other assembly language. To avoid truncating your pointer, cast it to a type of identical size. Use returnPtr[j] = (void *) ((long)ptr + i); ). How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? All float types are to be converted to double. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. What you do here is undefined behavior, and undefined behavior of very practical sort. Find centralized, trusted content and collaborate around the technologies you use most. If this is the data to a thread procedure, then you quite commonly want to pass by value. for (i=0, j=0; j
integer casts is implementation defined, but the intent was that if the pointer type is large enough and isn't forcefully aligned (, But that's different. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. 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. void* -> integer -> void* rather than integer -> void* -> integer. error: cast from pointer to smaller type 'unsigned int' loses information. C++ how to get the address stored in a void pointer? This is known as implicit type casting or type promotion, compiler automatically converts smaller data type to larger data type. Please help me compile Chez Scheme. What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? The problem was there before, you just are being notified of it. Why is there a voltage on my HDMI and coaxial cables? ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Pull requests. By clicking Sign up for GitHub, you agree to our terms of service and You are just making it bigger by tricking the compiler and the ABI. Have a question about this project? a is of type int[4], which can be implicitly cast to int* (ie, a pointer to an int) &a is of type int(*)[4] (ie: a pointer to an array of 4 ints). Does a summoned creature play immediately after being summoned by a ready action? A missing cast in the new fast > enumeration code. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. . You may declare a const int variable and cast its reference to the void*. If you need to keep the returned address, just keep it as void*. How do I count the number of sentences in C using ". SCAN_PUT(ATTR, NULL); SCAN_PUT_ATTR(key, ATTR, skey, FUNC); Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Star 675. 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. Not the answer you're looking for? My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? LLNL's tutorial is bad and they should feel bad. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. Identify those arcade games from a 1983 Brazilian music video. How Intuit democratizes AI development across teams through reusability. Thanks for contributing an answer to Stack Overflow! To learn more, see our tips on writing great answers. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini Usually that means the pointer is allocated with. 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 394k 35 393 602 1 Replacing broken pins/legs on a DIP IC package, How to handle a hobby that makes income in US. The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. @BlueMoon Thanks a lot! Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? What is the correct method to cast an int to a void*? ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ *sound/soc/codecs/tlv320aic32x4.c:1202:18: warning: cast to smaller integer type 'enum aic32x4_type' from 'void *' @ 2022-04-22 9:48 kernel test robot 0 siblings, 0 . Acidity of alcohols and basicity of amines. There is absolutely not gurantee that sizeof(int) <= sizeof(void*). So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. Already on GitHub? I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. 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. What does casting to void* does when passing arguments to variadic functions? 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. You can use any other pointer, or you can use (size_t), which is 64 bits. I agree passing a dynamically allocated pointer is fine (and I think the best way). Casting a pointer to void* and back is valid use of reinterpret_cast<>. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. The int data type is the primary integer data type in SQL Server. It modifies >> Wconversion-real.c, Wconversion-real-integer.c and pr35635.c to be more >> specific > > If the patch passes existing tests, I'd be inclined to leave them > tests alone and add new ones that are specific to what this patch > changes. Disconnect between goals and daily tasksIs it me, or the industry? This is why you got Error 1 C2036, from your post. error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. @Shahbaz you could but I will not suggest to a C newbie to use globals. It is done by the compiler on its own, without any external trigger from the user. @Xax: Here's a fixed version, without the race condition: gist.github.com/depp/241d6f839b799042c409, gist.github.com/depp/3f04508a88a114734195, How Intuit democratizes AI development across teams through reusability. 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. Otherwise, if the original pointer value points to an object a, and there is an object b of the . Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? If you are going to pass the address you typically need to exert some more control over the lifetime of the object. 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). Note the difference between the type casting of a variable and type casting of a pointer. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Why do academics stay as adjuncts for years rather than move around? Next, when doing pointer arithmetic, the addition operation will use the pointer's type to determine how many bytes to add to it when incrementing it. Making statements based on opinion; back them up with references or personal experience. If that happens soon after the call to pthread_create() then you have a race condition, because there's a chance that the thread will attempt to read x's value after it's life has ended, which invokes undefined behavior. ^~~~~~~~~~~~~~~~~~~ While working with Threads in C, I'm facing the warning, "warning: cast to pointer from integer of different size". Not the answer you're looking for? STR34-C. - the incident has nothing to do with me; can I use this this way? Why did Ukraine abstain from the UNHRC vote on China? Thanks. Identify those arcade games from a 1983 Brazilian music video, Relation between transaction data and transaction id, The difference between the phonemes /p/ and /b/ in Japanese. Floating-point conversions 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. unsigned long call_fn = (unsigned long)FUNC; You use the address-of operator & to do that. 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. This page was last modified on 12 February 2023, at 18:25. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. If int is no larger than pointer to void then one way to store the value is by simply copying the bytes: int i . 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). 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Such a downcast makes no runtime checks to ensure that the object's runtime type is actually D, and may only be used safely if this precondition is guaranteed by other means, such as when implementing static polymorphism. 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. If the destination type is bool, this is a boolean conversion (see below). 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. Yesterday, I updated Xcode to the newest version (5.1 (5B130a)) to compatible with iOS 7.1. with ids being an array of ints and touch being a pointer. 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. Find centralized, trusted content and collaborate around the technologies you use most. If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. For the Nozomi from Shinagawa to Osaka, say on a Saturday afternoon, would tickets/seats typically be available - or would you need to book? Is it possible to create a concave light? The following program casts a double to an int. actually no, as int my be a smaller type than a pointer ;-) But, of course with int64_t it works fine. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. Implementing From will result in the Into implementation but not vice-versa. rev2023.3.3.43278. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Noncompliant Code Example (memset())For historical reasons, certain C Standard functions accept an argument of type int and convert it to either unsigned char or plain char. This is a fine way to pass integers to new pthreads, if that is what you need. In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. reinterpret_cast is a type of casting operator used in C++. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. If pointers are 64 bits and ints are 32 bits, an int is too small to hold a pointer value. 471,961 Members | 900 Online. Can I tell police to wait and call a lawyer when served with a search warrant? 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. However, you are also casting the result of this operation to (void*). What video game is Charlie playing in Poker Face S01E07? He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. Whats the grammar of "For those whose stories they are"? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Just edited. lexborisov Modest Public. should we also have a diagnostic for the (presumed) user error? Such pointers can be stored in 32-bit data types (for instance, int, DWORD). Cast characters to unsigned char before converting to larger integer sizes Created by Robert Seacord, last modified by Jill Britton on Oct 03, 2022 Signed character data must be converted to unsigned char before being assigned or converted to a larger signed type. Using Kolmogorov complexity to measure difficulty of problems? I think the solution 3> should be the correct one. Error while setting app icon and launch image in xcode 5.1. how to cascade 2d int array to 2d void pointer array? Can I tell police to wait and call a lawyer when served with a search warrant? I assumed that gcc makes a 65536 out of my define, but I was wrong. A void pointer can be really useful if the programmer is not sure about the data type of data inputted by the end user. For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. The problem is not with casting, but with the target type loosing half of the pointer. ), For those who are interested. Taking the above declarations of A, D, ch of the . I don't see how anything bad can happen . The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS, AC Op-amp integrator with DC Gain Control in LTspice, Identify those arcade games from a 1983 Brazilian music video. A long long would not work for 32bit systems and a long would not work for 64 bit Windows (while 64bit Unix and Unix-like systems like OS X use the LP64 data model, in which a long is 64bit, 64bit Windows uses the LLP64 data model, in which a long has a size of 32bit (http://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models)). Use #include to define it. Thank you all for your feedback. 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; Converting a void* to an int is non-portable way that may work or may not! Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Is pthread_join a must when using pthread in linux? A nit: in your version, the cast to void * is unnecessary. Infact I know several systems where that does not hold.
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