It's an int type guaranteed to be big enough to contain a pointer. How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. How Intuit democratizes AI development across teams through reusability. What does casting to void* does when passing arguments to variadic functions? 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. Here is my code: I already tried (void*)M_TABLE_SIZE but then I get an error that I cannot use the * operator. Is it possible to create a concave light? What you do here is undefined behavior, and undefined behavior of very practical sort. I think the solution 3> should be the correct one. rev2023.3.3.43278. You are getting warnings due to casting a void* to a type of a different size. There's no proper way to cast this to int in general case. An open (void) pointer can hold a pointer of any type. That could create all kinds of trouble. Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. Most answers just try to extract 32 useless bits out of the argument. 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, Acidity of alcohols and basicity of amines. The following behavior-changing defect reports were applied retroactively to previously published C++ standards. If you cast an int pointer int, you might get back a different integer. How create a simple program using threads in C? */ >> -bool >> +enum conversion_safety >> unsafe_conversion_p (tree type, tree expr, bool . Making statements based on opinion; back them up with references or personal experience. Connect and share knowledge within a single location that is structured and easy to search. If the object expression refers or points to is actually a base class subobject of an object of type D, the result refers to the enclosing object of type D. Otherwise, the behavior is undefined: When the target type is bool (possibly cv-qualified), the result is false if the original value is zero and true for all other values. rev2023.3.3.43278. How do I check if a string represents a number (float or int)? 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). 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. If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. 10) A prvalue of type pointer to void (possibly cv-qualified) can be converted to pointer to any object type. -1, Uggh. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. what happens when we typecast normal variable to void* or any pointer variable? The difference between a and &a is the type. @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. Using Kolmogorov complexity to measure difficulty of problems? Click to see the query in the CodeQL repository. Implementing From will result in the Into implementation but not vice-versa. And then assign it to the double variable. Why did Ukraine abstain from the UNHRC vote on China? However even though their types are different, the address is going to be the same. Any help with this is appreciated. whether it was an actual problem is a different matter though. FAILED: lib/libopenvswitch.a.p/odp-util.c.obj This solution is in accordance with INT18-C. warning C4311: 'type cast': pointer truncation from 'void *' to 'long' in ECPG test files. 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! long guarantees a pointer size on Linux on any machine. The problem just occur with Xcode 5.1. Safe downcast may be done with dynamic_cast. Since gcc compiles that you are performing arithmetic between void* and an int (1024). itch" "-I..\include\windows" "-Iinclude" "-I..\include" "-I..\datapath-windows\include" "-IC:\PTHREADS-BUILT\include" "-Xclang" "-fcolor-diagnostics" "-pipe" reinterpret_cast<void *>(42)). 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). This forum has migrated to Microsoft Q&A. The problem was there before, you just are being notified of it. It is done by the compiler on its own, without any external trigger from the user. If the destination type is bool, this is a boolean conversion (see below). ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The program can be set in such a way to ask the user to inform the type of data and . this way I convert an int to a void* which is much better than converting a void* to an int. Yeah, the tutorial is doing it wrong. 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. Recovering from a blunder I made while emailing a professor. 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. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? rev2023.3.3.43278. I'm unfamiliar with XCode, but the solution should be something like follows: Most of the "solutions" above can lose part of the pointer address when casting to a smaller type. It solved my problem too. To access the object value, use the * dereference operator: int * p; assert (p == null ); p = new int (5); assert (p != null ); assert (*p == 5); (*p)++; assert (*p == 6); If a pointer contains a null value, it is not pointing to a valid object. What does it mean to convert int to void* or vice versa? ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. 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. (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. C/C++ , Cerror: cast to 'void *' from smaller integer type 'int'. 471,961 Members | 900 Online. ../lib/odp-util.c:5489:33: note: expanded from macro 'SCAN_PUT_ATTR' There's no proper way to cast this to int in general case. 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. I'm trying to create a void* from an int. 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. How do I set, clear, and toggle a single bit? From the question I presume the OP does. If you are going to pass the address you typically need to exert some more control over the lifetime of the object. The most general answer is - in no way. 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. 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. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. ), For those who are interested. But assuming that it is, as long as the caller and the callee agree, you can do that sort of thing. 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. *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 . @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. Put your define inside a bracket: without a problem. Are there tables of wastage rates for different fruit and veg? There's probably little you can do except look or hope for a fixed 2.x version or upgrade to 3.x (I would assume it's 64-bit safe but this is just a guess, do research this issue before you upgrade). It is easier to understand and write than any other assembly language. 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. a cast of which the programmer should be aware of what (s)he is doing. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. what does it mean to convert int to void* or vice versa? B language was designed to develop . I am compiling this program in linux gcc compiler.. 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". return ((void **) returnPtr);} /* Matrix() */. And when assigning to a void pointer, all type information is lost. Have a question about this project? 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. 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. this way you won't get any warning. I have a two functions, one that returns an int, and one that takes a const void* as an argument. Bulk update symbol size units from mm to map units in rule-based symbology. Windows has 32 bit long only on 64 bit as well. you can just change architecture to support 32 bit compilation by all below in in Build Settings. Converting one datatype into another is known as type casting or, type-conversion. ERROR: incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int', error: cast to 'string' (aka 'char *') from smaller integer type 'int' [-Werror,-Wint-to-pointer-cast], error: incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int' C, warning: initialization of 'unsigned char' from 'uint8_t *' {aka 'unsigned char *'} makes integer from pointer without a cast [-Wint-conversion], Minimising the environmental effects of my dyson brain. Since all pointers on 64-bit Windows are 64 bits, you are growing the data size from 32 bits backto 64 bits. 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. Basically its a better version of (void *)i. A nit: in your version, the cast to void * is unnecessary. I'm using cocos2d-x-2.2.2. No idea how it amassed 27 upvotes?! Asking for help, clarification, or responding to other answers. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. ^~~~~~~~~~~~~~~~~~~ } SCAN_END_SINGLE(ATTR) Why is there a voltage on my HDMI and coaxial cables? @BlueMoon Thanks a lot! Typically, long or unsigned long is . Making statements based on opinion; back them up with references or personal experience. Connect and share knowledge within a single location that is structured and easy to search. Implicit Type Conversion is also known as 'automatic type conversion'. I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . "-I.." "-Iinclude\openflow" "-I..\include\openflow" "-Iinclude\openvswitch" "-I..\include\openvsw To learn more, see our tips on writing great answers. SQL Server does not automatically promote . Use returnPtr[j] = (void *) ((long)ptr + i); ). Using indicator constraint with two variables. Maybe you can try this too. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. Does a summoned creature play immediately after being summoned by a ready action? If the function had the correct signature you would not need to cast it explicitly. Visit Microsoft Q&A to post new questions. Here, the Java first converts the int type data into the double type. Making statements based on opinion; back them up with references or personal experience. and how to print the thread id of 2d array argument? Thanks for pointing that out. Notifications. This will only compile if the destination type is long enough. Asking for help, clarification, or responding to other answers. This is what the second warning is telling you. eg. GitHub. Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. Can Martian regolith be easily melted with microwaves? You use the address-of operator & to do that. Identify those arcade games from a 1983 Brazilian music video. should we also have a diagnostic for the (presumed) user error? Why is this sentence from The Great Gatsby grammatical? p-util.c.obj "-c" ../lib/odp-util.c A cast specifies a conversion from one type to another. There is no "correct" way to store a 64-bit pointer in an 32-bit integer. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. Find centralized, trusted content and collaborate around the technologies you use most. Here is some piece of code where that error occur: /cocos2d-x-2.2.2/cocos2dx/platform/ios/EAGLView.mm:408:18: Cast from pointer to smaller type 'int' loses information. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. 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. It was derived from the BCPL, and the name of the b language is possibly from the BCPL contraction. Thank you all for your feedback. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] What video game is Charlie playing in Poker Face S01E07? 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. LLNL's tutorial is bad and they should feel bad. Update: Today, i download the latest version of cocos2d-x (cocos2d-x 2.2.3). Note:You might receive a runtime exception if the pointer contains a value unsuitable for the context. The bigint data type is intended for use when integer values might exceed the range that is supported by the int data type.. bigint fits between smallmoney and int in the data type precedence chart.. Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. Type casting is when you assign a value of one primitive data type to another type. @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. 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). Functions return bigint only if the parameter expression is a bigint data type. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? ^~~~~~~~~~~~~~~~~~~~ Is pthread_join a must when using pthread in linux? However, you are also casting the result of this operation to (void*). If the value is ever used as pointer again that will prove to be an extremely bad idea. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. SCAN_PUT(ATTR, NULL); 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. C / C++ Forums on Bytes. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). unsigned long call_fn = (unsigned long)FUNC; converted back to pointer to void, and the result will compare equal Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). How to notate a grace note at the start of a bar with lilypond? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. If your standard library (even if it is not C99) happens to provide these types - use them. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Xcode 5 and iOS 7: Architecture and Valid architectures, xcode build error: Semantic issue cast from pointer to smaller type 'int' loses information, Issues in handling touches on subviews(uiviews) in UIScrollView, Architecture linking error after Xcode 5.1 upgrade, iOS 7.1 gives error after updating to Xcode 5.1, Linker error in Xcode 5.1 with cocos2d-x 3 beta 2. In the case of Widening Type Casting, the lower data type (having smaller size) is converted into the higher data type (having larger size). So,solution #3 works just fine. You can convert the values from one type to another explicitly using the cast operator as follows (type_name) expression Find centralized, trusted content and collaborate around the technologies you use most. 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. Then i can continue compiling. Why does setupterm terminate the program? Press question mark to learn the rest of the keyboard shortcuts. Once you manage to make this cast, then what?! You are just making it bigger by tricking the compiler and the ABI. 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 Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. I don't see how anything bad can happen . You can fix this error by replacing this line of code. Otherwise, if the original pointer value points to an object a, and there is an object b of the . How do I count the number of sentences in C using ". For integer casts in specific, using into() signals that . Api says this is how i should create thread: So if I want to pass an int what I think I should do is: The second example assumes that a pointer is wide enough to store an int. Therefore, you need to change it to long long instead of long in windows for 64 bits. Again, all of the answers above missed the point badly. Find centralized, trusted content and collaborate around the technologies you use most. @Martin York: No, it doesn't depend on endiannness. Star 675. (int*)Pc = pa; After the execution of the above code all the three pointers, i.e., Pa, Pd, and Pc, point to the value 150. Do new devs get fired if they can't solve a certain bug? If your standard library (even if it is not C99) happens to provide these types - use them. Such pointers can be stored in 32-bit data types (for instance, int, DWORD). BUT converting a pointer to void* and back again is well supported (everywhere). So make sure you understand what you are doing! Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). The cast back to int * is not, though. Replacing broken pins/legs on a DIP IC package, How to handle a hobby that makes income in US.
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