To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Then I build my project, I get the error "Cast from pointer to smaller type 'int' loses information" in EAGLView.mm file (line 408) when 64-bit simulators (e.g. The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Basically its a better version of (void *)i. Can I tell police to wait and call a lawyer when served with a search warrant? ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' The value of float variable is= 37.75. converted back to pointer to void, and the result will compare equal Thanks for contributing an answer to Stack Overflow! Apparently the clang version in Xcode 5.1 and above is more strict about potential 32bit vs. 64 bit incompatibilities in source code than older clang versions have been. Casting arguments inside the function is a lot safer. cast to 'double *' from smaller integer type 'unsigned int' The C compiler is gcc, clang version 3.9.1, target aarch64--linux-android, thread model posix. As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. You are right! Thanks for contributing an answer to Stack Overflow! Find centralized, trusted content and collaborate around the technologies you use most. 1. @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. ncdu: What's going on with this second size column? 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. Making statements based on opinion; back them up with references or personal experience. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. If you call your thread creation function like this, then the void* arriving inside of myFcn has the value of the int you put into it. windows meson: cast to smaller integer type 'unsigned long' from 'void *'. 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. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. If the value in a pointer is cast to a different type and it does not have the correct alignment for the new type, the behavior is undefined. Mutually exclusive execution using std::atomic? Replacing broken pins/legs on a DIP IC package, AC Op-amp integrator with DC Gain Control in LTspice. Why do academics stay as adjuncts for years rather than move around? Just edited. Connect and share knowledge within a single location that is structured and easy to search. If any, how can the original function works without errors if we just ignore the warning. Find centralized, trusted content and collaborate around the technologies you use most. It is purely a compile-time directive which instructs the compiler to treat expression as if it had . warning C4311: 'type cast': pointer truncation from 'void *' to 'long' in ECPG test files. This is what the second warning is telling you. Hence there is no loss in data. - the incident has nothing to do with me; can I use this this way? unsigned long call_fn = (unsigned long)FUNC; I'm trying to learn pthreads and thing that keeps bugging me is how do i really pass argument to the function. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. If this is the data to a thread procedure, then you quite commonly want to pass by value. Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. Half your pointer will be garbage. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? As with all cast expressions, the result is: Two objects a and b are pointer-interconvertible if: static_cast may also be used to disambiguate function overloads by performing a function-to-pointer conversion to specific type, as in. Using indicator constraint with two variables. Is it possible to create a concave light? Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? You think by casting it here that you are avoiding the problem! Whats the grammar of "For those whose stories they are"? Error while setting app icon and launch image in xcode 5.1. The proper way is to cast it to another pointer type. Does Counterspell prevent from any further spells being cast on a given turn? What does it mean to convert int to void* or vice versa? *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 . vegan) just to try it, does this inconvenience the caterers and staff? To learn more, see our tips on writing great answers. byte -> short -> char -> int -> long -> float -> double. error: cast from pointer to smaller type 'unsigned int' loses information. The calculated expression consists of two operations. Why is this sentence from The Great Gatsby grammatical? Issues. Notifications. If the destination type is bool, this is a boolean conversion (see below). Asking for help, clarification, or responding to other answers. p-util.c.obj "-c" ../lib/odp-util.c pthread passes the argument as a void*. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. The preprocesor absolutely will not perform arithmetic. Yeah, the tutorial is doing it wrong. Is it possible to create a concave light? Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. Bulk update symbol size units from mm to map units in rule-based symbology. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. Not the answer you're looking for? 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. However the actual code in question contains an explicit c-style cast to int. 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. should we also have a diagnostic for the (presumed) user error? For a fairly recent compiler (that supports C99) you should not store or represent address as plain int value. Maybe you can try this too. That's not a good idea if the original object (that was cast to void*) was an integer. 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? You could use this code, and it would do the same thing as casting ptr to (char*). rev2023.3.3.43278. How to convert a factor to integer\numeric without loss of information? How can this new ban on drag possibly be considered constitutional? I recall there was a TreeNode(int) early on prior to 1.0 release I can't remember why I removed it, if I should felt it was easy enough to cast to (void*) or if it was because it created type inference conflict at the call site. This page has been accessed 1,655,678 times. Casting int to void* loses precision, and what is the solution in required cases, c++: cast from "const variable*" to "uint32" loses precision, Recovering from a blunder I made while emailing a professor, Relation between transaction data and transaction id. How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? 10) A prvalue of type pointer to void (possibly cv-qualified) can be converted to pointer to any object type. While working with Threads in C, I'm facing the warning, "warning: cast to pointer from integer of different size". "I think what you should do is actually pass the address of the variable to the function" Not necessarily. property that any valid pointer to void can be converted to this type, To learn more, see our tips on writing great answers. Terrible solution. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? How do I set, clear, and toggle a single bit? What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? 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. Difficulties with estimation of epsilon-delta limit proof. 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. A nit: in your version, the cast to void * is unnecessary. Or, they are all wrong. How do I check if a string represents a number (float or int)? 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" (. Does melting sea ices rises global sea level? Thus as a result it may be less error prone to generate a pointer dynamcially and use that. x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. what does it mean to convert int to void* or vice versa? The int data type is the primary integer data type in SQL Server. Find centralized, trusted content and collaborate around the technologies you use most. "-I.." "-Iinclude\openflow" "-I..\include\openflow" "-Iinclude\openvswitch" "-I..\include\openvsw The mapping in pointer<->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. In a 64bit build a pointer is 64bit (contrary to a 32bit build, where it is 32bit), while an int is 32bit, so this assignment stores a 64bit value in a 32bit storage, which may result in a loss of information. A sane compiler may throw a warning on lines like this but by no way it should throw an error, because this code is NOT wrong, it is just potentially error-prone, but can be perfectly valid. This explicit cast clearly tells the compiler "Shut up, I know that this code does not look correct, but I do know what I am doing". Making statements based on opinion; back them up with references or personal experience. 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. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. This is flat out wrong. What happens if you typecast as unsigned first? Why is there a voltage on my HDMI and coaxial cables? Connect and share knowledge within a single location that is structured and easy to search. 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). I am compiling this program in linux gcc compiler.. It's always a good practice to put your #define's in brackets to avoid such surprise. Windows has 32 bit long only on 64 bit as well. 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. STR34-C. 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. Properly casting a `void*` to an integer in C++ 24,193 Solution 1 I think using intptr_t is the correct intermediate here, since it's guaranteed to be large enough to contain the integral value of the void*, and once I have an integer value I can then truncate it without causing the compiler to complain. Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. As a result of the integer division 3/2 we get the value 1, which is of the int type. Casting an open pointer to other pointer types and casting other pointer types to an open pointer does not result in a compile time error. Thanks for pointing that out. I wish that you write those answer first than the explanation. 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. From that point on, you are dealing with 32 bits. How to correctly cast a pointer to int in a 64-bit application? Then i can continue compiling. So make sure you understand what you are doing! and how to print the thread id of 2d array argument? The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. If it's anything like cocos2d-iphone v2.x and just based on this slice of code in a core class I wager it's safe to say that cocos2d-x 2.x also is not compatible with 64 bit code, and you can expect all kinds of issues (not just compile-time but also runtime). To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Just re-enforcing the old behavior of Xcode 5.0 and earlier versions, that already cut away parts of the address by casting it to int, won't introduce any new bugs and avoids the need to learn and understand lots of implementation-internal cocos code. Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. Find centralized, trusted content and collaborate around the technologies you use most. Functions return bigint only if the parameter expression is a bigint data type. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. In such a case the programmer can use a void pointer to point to the location of the unknown data type. Asking for help, clarification, or responding to other answers. Is a PhD visitor considered as a visiting scholar. . Taking the above declarations of A, D, ch of the . ", "? ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' rev2023.3.3.43278. static_cast on the other hand should deny your stripping away the const qualifier. Create an account to follow your favorite communities and start taking part in conversations. Converting one datatype into another is known as type casting or, type-conversion. Connect and share knowledge within a single location that is structured and easy to search. Floating-point conversions even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" ../lib/odp-util.c:5489:33: note: expanded from macro 'SCAN_PUT_ATTR' itch" "-I..\include\windows" "-Iinclude" "-I..\include" "-I..\datapath-windows\include" "-IC:\PTHREADS-BUILT\include" "-Xclang" "-fcolor-diagnostics" "-pipe" Why did Ukraine abstain from the UNHRC vote on China? whether it was an actual problem is a different matter though. 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 do that. @DavidHeffernan I rephrased that sentence a little. Is pthread_join a must when using pthread in linux? 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. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. What is the purpose of non-series Shimano components? 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 Find centralized, trusted content and collaborate around the technologies you use most. SQL Server does not automatically promote . This is an old C callback mechanism so you can't change that. No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. 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. linux c-pthreads: problem with local variables. Why do small African island nations perform better than African continental nations, considering democracy and human development? What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. . Thanks for contributing an answer to Stack Overflow! GitHub. On all of them int is 32bit, not 16bit. If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. The preprocessor will replace your code by this: This is unlikely what you are trying to do. (int) pthread_self() 64int48intuintptr_t (unsigned int) By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Disconnect between goals and daily tasksIs it me, or the industry? Can Martian regolith be easily melted with microwaves? The difference between the phonemes /p/ and /b/ in Japanese. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. 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. If you preorder a special airline meal (e.g. 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: I am using size_t here, because it is always having the same size as a pointer, no matter the platform. @DietrichEpp can you explain what is race condition with using. [] ExplanatioUnlike static_cast, but like const_cast, the reinterpret_cast expression does not compile to any CPU instructions (except when converting between integers and pointers or on obscure architectures where pointer representation depends on its type). reinterpret_cast is a type of casting operator used in C++. Instead of using a long cast, you should cast to size_t. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. 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)).

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