Any expression can be cast to type void (which means that the result of the expression is ignored), but it's not legal to cast an expression of type void to type int not least because the result of such a cast wouldn't make any sense. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); You are just making it bigger by tricking the compiler and the ABI. Note:You might receive a runtime exception if the pointer contains a value unsuitable for the context. Casting int to void* : r/C_Programming - reddit cast operators [edit] When an expression is used in the context where a value of a different type is expected, conversionmay occur: intn =1L;// expression 1L has type long, int is expectedn =2.1;// expression 2.1 has type double, int is expectedchar*p =malloc(10);// expression malloc(10) has type void*, char* is expected To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. If you preorder a special airline meal (e.g. Thanks for contributing an answer to Stack Overflow! returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size); 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. INT31-C. Ensure that integer conversions do not result in lost or . 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. Terrible solution. 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". Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). I'm using cocos2d-x-2.2.2. 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 think what you should do is actually pass the address of the variable to the function" Not necessarily. equal to the original pointer: First you are using a define, which is not a variable. 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. I am compiling this program in linux gcc compiler.. It solved my problem too. Can Martian regolith be easily melted with microwaves? Basically its a better version of (void *)i. Functions return bigint only if the parameter expression is a bigint data type. Why did Ukraine abstain from the UNHRC vote on China? You are getting warnings due to casting a void* to a type of a different size. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? Not the answer you're looking for? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. Cast Operations - Oracle If you cast an int pointer int, you might get back a different integer. And, most of these will not even work on gcc4. This example is noncompliant on an implementation where pointers are 64 bits and unsigned integers are 32 bits because the result of converting the 64-bit ptr cannot be represented in the 32-bit integer type. Does a summoned creature play immediately after being summoned by a ready action? If the destination type is bool, this is a boolean conversion (see below). } SCAN_END_SINGLE(ATTR) There is absolutely not gurantee that sizeof(int) <= sizeof(void*). How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? 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. Use #include to define it. ^~~~~~~~~~~~~~~~~~~~~ What does it mean to convert int to void* or vice versa? However the actual code in question contains an explicit c-style cast to int. I cannot reverse my upvote of user384706's answer, but it's wrong. Click to see the query in the CodeQL repository. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Get the address of a callback function to call dynamically in C++, error: call of overloaded function ambiguous, error: cast from to unsigned int loses precision [-fpermissive]. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? *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 . Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. That could create all kinds of trouble. Yeah, the tutorial is doing it wrong. Thanks. Bulk update symbol size units from mm to map units in rule-based symbology. ", "!"? In the case of Widening Type Casting, the lower data type (having smaller size) is converted into the higher data type (having larger size). Find centralized, trusted content and collaborate around the technologies you use most. 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. 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;. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? 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. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' Connect and share knowledge within a single location that is structured and easy to search. Asking for help, clarification, or responding to other answers. Find centralized, trusted content and collaborate around the technologies you use most. Identify those arcade games from a 1983 Brazilian music video. 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). The preprocesor absolutely will not perform arithmetic. This is why you got Error 1 C2036, from your post. Making statements based on opinion; back them up with references or personal experience. : iPhone Retina 4-inch 64-bit) is selected. How to convert a factor to integer\numeric without loss of information? ", "? This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. Implicit Type Conversion in C with Examples - GeeksforGeeks ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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. In such a case the programmer can use a void pointer to point to the location of the unknown data type. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Not the answer you're looking for? a cast of which the programmer should be aware of what (s)he is doing. Connect and share knowledge within a single location that is structured and easy to search. - the incident has nothing to do with me; can I use this this way? The problem was there before, you just are being notified of it. Find centralized, trusted content and collaborate around the technologies you use most. How to use Slater Type Orbitals as a basis functions in matrix method correctly? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Evaluate integer expressions in a larger size before comparing or assigning to that size.Note that (time_+t)-1 also complies with INT31-C-EX3. ../lib/odp-util.c:5601:9: note: expanded from macro 'SCAN_PUT' Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. 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). Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? Casting type int to const void* - C / C++ Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. casting from int to void* and back to int. Type Casting in C Language with Examples - Dot Net Tutorials Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin? B language was designed to develop . Fork 63. Clang warnings for an invalid casting? - The FreeBSD Forums rev2023.3.3.43278. C/C++ , Cerror: cast to 'void *' from smaller integer type 'int'. Converting a void* to an int is non-portable way that may work or may not! Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul What is the purpose of non-series Shimano components? If the original pointer value represents an address of a byte in memory that does not satisfy the alignment requirement of the target type, then the resulting pointer value is unspecified. @jackdoe: It's a waste of human life to write code that "you may need in the future". What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? I get the error: "cast to smaller integer type 'int' from 'string' (aka 'char *')" referencing line of code: while (isalpha(residents[i].name) == 0), How Intuit democratizes AI development across teams through reusability. You could use this code, and it would do the same thing as casting ptr to (char*). If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. and how to print the thread id of 2d array argument? Disconnect between goals and daily tasksIs it me, or the industry? The most general answer is - in no way. 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. 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. ncdu: What's going on with this second size column? But the problem has still happened. The problem just occur with Xcode 5.1. For the remaining integral types, the result is the value of the enum if it can be represented by the target type and unspecified otherwise. How to use Slater Type Orbitals as a basis functions in matrix method correctly? But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. Casting Pointers - IBM It's an int type guaranteed to be big enough to contain a pointer. Making statements based on opinion; back them up with references or personal experience. You may declare a const int variable and cast its reference to the void*. Thanks for contributing an answer to Stack Overflow! Disconnect between goals and daily tasksIs it me, or the industry? 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. A nit: in your version, the cast to void * is unnecessary. Put your define inside a bracket: without a problem. SCAN_PUT(ATTR, NULL); Using Kolmogorov complexity to measure difficulty of problems? All character types are to be converted to an integer. Type Casting Of Pointers in C - Computer Notes What video game is Charlie playing in Poker Face S01E07? Netdev Archive on lore.kernel.org help / color / mirror / Atom feed * [mst-vhost:vhost 5/52] drivers/block/virtio_blk.c:539:21: warning: assignment to 'void *' from . The cast back to int * is not, though. error: cast from 'void*' to 'int' loses precision - Stack Overflow I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. 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. Why is there a voltage on my HDMI and coaxial cables? 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. So,solution #3 works just fine. Otherwise, if the original pointer value points to an object a, and there is an object b of the . To subscribe to this RSS feed, copy and paste this URL into your RSS reader. This will only compile if the destination type is long enough. Is pthread_join a must when using pthread in linux? SCAN_PUT_ATTR(mask, ATTR, smask, FUNC); What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. For integer casts in specific, using into() signals that . rev2023.3.3.43278. If the function had the correct signature you would not need to cast it explicitly. this question. The calculated expression consists of two operations. If we want to get the exact value of 7/5 then we need explicit casting from int to float: Example: int x=7, y=5; rev2023.3.3.43278. Now, what happens when I run it with the thread sanitizer? @Shahbaz you could but I will not suggest to a C newbie to use globals. Getting Command /bin/sh failed with exit code 65 Error with Xcode 5.1 . byte -> short -> char -> int -> long -> float -> double. The following program casts a double to an int. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. The value of float variable is= 37.75. You use the address-of operator & to do that. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. LLNL's tutorial is bad and they should feel bad. 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. When is casting void pointer needed in C? Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. Don't do that. Java Type Casting. reinterpret_cast<void *>(42)). What happens if you typecast as unsigned first? To learn more, see our tips on writing great answers. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. Again, all of the answers above missed the point badly. If your standard library (even if it is not C99) happens to provide these types - use them. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. If the value is ever used as pointer again that will prove to be an extremely bad idea. linux c-pthreads: problem with local variables. Using indicator constraint with two variables. Asking for help, clarification, or responding to other answers. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Windows has 32 bit long only on 64 bit as well. This is not even remotely "the correct answer". C - Type Casting - tutorialspoint.com Not the answer you're looking for? ncdu: What's going on with this second size column? This is what the second warning is telling you. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Visit Microsoft Q&A to post new questions. How to Cast a void* ponter to a char without a warning? ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' Thanks for pointing that out. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini I agree passing a dynamically allocated pointer is fine (and I think the best way). ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' On many systems, an 8-bit unsigned int can be stored at any address while an unsigned 32-bit int must be aligned on an address that is a multiple of 4. Do new devs get fired if they can't solve a certain bug? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. 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? The subreddit for the C programming language, Press J to jump to the feed. } SCAN_END_SINGLE(ATTR) Once you manage to make this cast, then what?! */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size); for (i=0, j=0; j returnPtr[j] = (void *) (ptr + i); // <<< Compile Errors, Error1error C2036: 'void *' : unknown sizec:\temp\testone\lib\utils.c57, 2> returnPtr[j] = (void *) ((long*)ptr + i); // <<< No compile errors, 3> returnPtr[j] = (void *) ((char*)ptr + i); // <<< No compile errors. My code is all over the place now but I appreciate you all helping me on my journey to mastery! whether it was an actual problem is a different matter though. On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. Just edited. 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. Cerror: cast to 'void *' from smaller integer type 'int' In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. There's no proper way to cast this to int in general case. Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. I assumed that gcc makes a 65536 out of my define, but I was wrong. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. The text was updated successfully, but these errors were encountered: You signed in with another tab or window. It is purely a compile-time directive which instructs the compiler to treat expression as if it had . how to cascade 2d int array to 2d void pointer array? What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? This page was last modified on 12 February 2023, at 18:25. Converts between types using a combination of implicit and user-defined conversions. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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". Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? I need to cast the int from the first function so that I can use it as an argument for the second function. The difference between the phonemes /p/ and /b/ in Japanese. Mutually exclusive execution using std::atomic? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. 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. ^~~~~~~~~~~~~~~~~~~~ sound/soc/codecs/tlv320aic32x4.c:1202:18: warning: cast to smaller By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. You just need to suppress the warning, and this will do it: This may offend your sensibilities, but it's very short and has no race conditions (as you'd have if you used &i). Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? "clang" "-Ilib\libopenvswitch.a.p" "-Ilib" "-I..\lib" "-I." /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? 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. ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' The text was updated successfully, but these errors were encountered: It is easier to understand and write than any other assembly language. How do I force make/GCC to show me the commands? Why do small African island nations perform better than African continental nations, considering democracy and human development? this way you won't get any warning. And in this context, it is very very very common to see programmers lazily type cast the. eg. ^~~~~~~~~~~~~~~~~~~~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. (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. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Based on the design of this function, which modification is right. 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)). But this code pass the normal variable .. Bulk update symbol size units from mm to map units in rule-based symbology. rev2023.3.3.43278. If the source type is bool, the value false is converted to zero and the value true is converted to the value one of the destination type (note that if the destination type is int, this is an integer promotion, not an integer conversion). tialized" "-Wno-format" "-Wno-incompatible-pointer-types" "-Werror" "-dM" "-U_MSC_VER" "-D_TIMESPEC_DEFINED" "-D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_SECURE_NO_WA Recovering from a blunder I made while emailing a professor. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' Taking the above declarations of A, D, ch of the . I have a two functions, one that returns an int, and one that takes a const void* as an argument. 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. You can only do this if you use a synchronization primitive to ensure that there is no race condition. clang warnings in v1.42 Issue #265 ocornut/imgui GitHub 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. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. Remembering to delete the pointer after use so that we don't leak. windows meson: cast to smaller integer type 'unsigned long' from 'void Asking for help, clarification, or responding to other answers. To learn more, see our tips on writing great answers. Casting a pointer to void* and back is valid use of reinterpret_cast<>. Then i can continue compiling. Converting one datatype into another is known as type casting or, type-conversion. To avoid truncating your pointer, cast it to a type of identical size. 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.
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