cast to void *' from smaller integer type 'int

Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. ^~~~~~~~~~~~~~~~~~~ ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. 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. However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. Connect and share knowledge within a single location that is structured and easy to search. 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. void* -> integer -> void* rather than integer -> void* -> integer. } SCAN_END_SINGLE(ATTR) Bulk update symbol size units from mm to map units in rule-based symbology. This will only compile if the destination type is long enough. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. Instead of using a long cast, you should cast to size_t. Making statements based on opinion; back them up with references or personal experience. 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. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Setting a buffer of char* with intermediate casting to int*. Find centralized, trusted content and collaborate around the technologies you use most. 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. rev2023.3.3.43278. this way you won't get any warning. Asking for help, clarification, or responding to other answers. 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. If your standard library (even if it is not C99) happens to provide these types - use them. 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). Converting one datatype into another is known as type casting or, type-conversion. How to get the error message from the error code returned by GetLastError()? I am compiling this program in linux gcc compiler.. B language was designed to develop . The code ((void*)ptr + 1) does not work, because the compiler has no idea what size "void" is, and therefore doesn't know how many bytes to add. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. Using indicator constraint with two variables. 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). 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;. The preprocessor will replace your code by this: This is unlikely what you are trying to do. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' 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. It is done by the compiler on its own, without any external trigger from the user. Getting Command /bin/sh failed with exit code 65 Error with Xcode 5.1 . In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. 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 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). 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. But then you need to cast your arguments inside your thread function which is quite unsafe cf. a cast of which the programmer should be aware of what (s)he is doing. Thank you all for your feedback. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. What is the purpose of non-series Shimano components? But I'm nitpicking .. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Click to see the query in the CodeQL repository. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Thanks for pointing that out. Making statements based on opinion; back them up with references or personal experience. Using Kolmogorov complexity to measure difficulty of problems? From the question I presume the OP does. There is absolutely not gurantee that sizeof(int) <= sizeof(void*). How create a simple program using threads in C? 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 . Half your pointer will be garbage. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" Mutually exclusive execution using std::atomic? 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. If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. By clicking Sign up for GitHub, you agree to our terms of service and I cannot reverse my upvote of user384706's answer, but it's wrong. 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 */ >> -bool >> +enum conversion_safety >> unsafe_conversion_p (tree type, tree expr, bool . How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. ", "!"? Whats the grammar of "For those whose stories they are"? The most general answer is - in no way. I'm trying to learn pthreads and thing that keeps bugging me is how do i really pass argument to the function. 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. I have the following function and when I compile it under VS.NET 2005, the following compile warnings show up: Warning1warning C4311: 'type cast' : pointer truncation from 'void *' to 'long'c:\temp\testone\lib\utils.c56Warning2warning C4312: 'type cast' : conversion from 'unsigned long' to 'void *' of greater sizec:\temp\testone\lib\utils.c56, Code Snippet For integer casts in specific, using into() signals that . Implicit Type Conversion is also known as 'automatic type conversion'. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. "I think what you should do is actually pass the address of the variable to the function" Not necessarily. No idea how it amassed 27 upvotes?! ^~~~~~~~~~~~~~~~~~~~~ windows meson: cast to smaller integer type 'unsigned long' from 'void *'. 471,961 Members | 900 Online. Otherwise, if the original pointer value points to an object a, and there is an object b of the . This is what the second warning is telling you. If you preorder a special airline meal (e.g. This page was last modified on 12 February 2023, at 18:25. 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 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. lexborisov Modest Public. The following behavior-changing defect reports were applied retroactively to previously published C++ standards. Why do small African island nations perform better than African continental nations, considering democracy and human development? And, most of these will not even work on gcc4. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. vegan) just to try it, does this inconvenience the caterers and staff? How do I align things in the following tabular environment? To cast such pointers to 32-bit types and vice versa special functions are used: void * Handle64ToHandle ( const void * POINTER_64 h ) void * POINTER_64 HandleToHandle64 ( const void *h ) long HandleToLong ( const void *h ) unsigned long HandleToUlong ( const void *h ) How Intuit democratizes AI development across teams through reusability. A cast specifies a conversion from one type to another. To learn more, see our tips on writing great answers. Therefore it is perfectly valid for the compiler to throw an error for a line like. What happens if you typecast as unsigned first? @jackdoe: It's a waste of human life to write code that "you may need in the future". How Intuit democratizes AI development across teams through reusability. [that could be a TODO - not to delay solving the ICE]. Press question mark to learn the rest of the keyboard shortcuts. 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). Here is my code: I already tried (void*)M_TABLE_SIZE but then I get an error that I cannot use the * operator. (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. And in the function you get the value of the pointer by using the dereference operator *: Please read why glib provide macros for this kind of conversions, there's no need to repeat the text here. If you preorder a special airline meal (e.g. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. There's no proper way to cast this to int in general case. And then assign it to the double variable. Where does this (supposedly) Gibson quote come from? pthread passes the argument as a void*. This solution is in accordance with INT18-C. property that any valid pointer to void can be converted to this type, The problem was there before, you just are being notified of it. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? I have looked around and can't seem to find any information on how to do this. XCode 5.1 is change all architecture to 64 bit. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_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 can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? This is a fine way to pass integers to new pthreads, if that is what you need. So reinterpret_cast has casted it to long type and then static_cast safely casts long to int, if you are ready do truncte the data. Already on GitHub? 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)). B programing language is a language based on basic combined programming or a BCPL, and it is the precursor of the C programming language. 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. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. You are correct, but cocos actually only uses that address as a unique id. Thanks for contributing an answer to Stack Overflow! how to cascade 2d int array to 2d void pointer array? 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. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. Floating-point conversions That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. 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. GitHub Skip to content Product Solutions Open Source Pricing Sign in Sign up smadaminov / ovs-dpdk-meson-issues Public Notifications Fork 1 Star 1 Code Issues 66 Pull requests Actions Projects 1 Security Insights New issue To learn more, see our tips on writing great answers. 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. p-util.c.obj "-c" ../lib/odp-util.c How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. I agree passing a dynamically allocated pointer is fine (and I think the best way). Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). 1. Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Just edited. If any, how can the original function works without errors if we just ignore the warning. 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. LLNL's tutorial is bad and they should feel bad. Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. A missing cast in the new fast > enumeration code. It generally takes place when in an expression more than one data type is present. What video game is Charlie playing in Poker Face S01E07? casting from int to void* and back to int. How do I force make/GCC to show me the commands? Find centralized, trusted content and collaborate around the technologies you use most. ../lib/odp-util.c:5601:9: note: expanded from macro 'SCAN_PUT' Yeah, the tutorial is doing it wrong. If the function had the correct signature you would not need to cast it explicitly. 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. Put your define inside a bracket: without a problem. Thanks for contributing an answer to Stack Overflow! Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. LLNL's tutorial is bad and they should feel bad. What you do here is undefined behavior, and undefined behavior of very practical sort. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? This allows you to reinterpret the void * as an int. Find centralized, trusted content and collaborate around the technologies you use most. Disconnect between goals and daily tasksIs it me, or the industry? this question. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. Does Counterspell prevent from any further spells being cast on a given turn? You can fix this error by replacing this line of code. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. what does it mean to convert int to void* or vice versa? rev2023.3.3.43278. Based on the design of this function, which modification is right. I assumed that gcc makes a 65536 out of my define, but I was wrong. /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. and how to print the thread id of 2d array argument? Can I tell police to wait and call a lawyer when served with a search warrant? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Casting a pointer to void* and back is valid use of reinterpret_cast<>. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. My code is all over the place now but I appreciate you all helping me on my journey to mastery! In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. If your standard library (even if it is not C99) happens to provide these types - use them. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. All character types are to be converted to an integer. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Taking the above declarations of A, D, ch of the . Sign in How to convert a factor to integer\numeric without loss of information? 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); Use #include to define it. 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. 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. What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' The difference between the phonemes /p/ and /b/ in Japanese. Pull requests. If you cast an int pointer int, you might get back a different integer. Asking for help, clarification, or responding to other answers. 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. reinterpret_cast is a type of casting operator used in C++. Or, they are all wrong. Have a question about this project? equal to the original pointer: First you are using a define, which is not a variable. 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. Any help with this is appreciated. 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. 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! How to use Slater Type Orbitals as a basis functions in matrix method correctly? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. 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]. If this is the data to a thread procedure, then you quite commonly want to pass by value. The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. However even though their types are different, the address is going to be the same. 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). Connect and share knowledge within a single location that is structured and easy to search.

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