Star 675. 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). @jackdoe: It's a waste of human life to write code that "you may need in the future". Not the answer you're looking for? 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.. C++ how to get the address stored in a void pointer? And in this context, it is very very very common to see programmers lazily type cast the. 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. You are getting warnings due to casting a void* to a type of a different size. @BlueMoon Thanks a lot! 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 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. Find centralized, trusted content and collaborate around the technologies you use most. Now, what happens when I run it with the thread sanitizer? 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. Is a PhD visitor considered as a visiting scholar. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? } SCAN_END_SINGLE(ATTR) Not the answer you're looking for? How to use Slater Type Orbitals as a basis functions in matrix method correctly? actually no, as int my be a smaller type than a pointer ;-) But, of course with int64_t it works fine. How to get the error message from the error code returned by GetLastError()? Implementing From will result in the Into implementation but not vice-versa. (int) pthread_self() 64int48intuintptr_t (unsigned int) Put your define inside a bracket: #define M_TABLE_SIZE (64*1024) Now, you can do: static const void* M_OFFSET = (void*) M_TABLE_SIZE; without a problem. 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). All character types are to be converted to an integer. It's always a good practice to put your #define's in brackets to avoid such surprise. SCAN_PUT_ATTR(mask, ATTR, smask, FUNC); What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Well occasionally send you account related emails. What is the difference between const int*, const int * const, and int const *? Making statements based on opinion; back them up with references or personal experience. As a result of the integer division 3/2 we get the value 1, which is of the int type. Can I tell police to wait and call a lawyer when served with a search warrant? The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. C / C++ Forums on Bytes. - the incident has nothing to do with me; can I use this this way? You can convert the values from one type to another explicitly using the cast operator as follows (type_name) expression The reinterpret_cast makes the int the size of a pointer and the warning will stop. No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. What does it mean to convert int to void* or vice versa? 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 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. 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. Here, the Java first converts the int type data into the double type. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. use $(ARCHS_STANDARD_32_BIT) at Architecture instead of $(ARCHS_STANDARD). What is the correct method to cast an int to a void*? I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . So,solution #3 works just fine. 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 x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. But this code pass the normal variable .. Half your pointer will be garbage. How can this new ban on drag possibly be considered constitutional? converted back to pointer to void, and the result will compare equal 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 wish that you write those answer first than the explanation. Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. Note the difference between the type casting of a variable and type casting of a pointer. Why does setupterm terminate the program? If pointers are 64 bits and ints are 32 bits, an int is too small to hold a pointer value. However even though their types are different, the address is going to be the same. Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. How do I force make/GCC to show me the commands? SCAN_PUT(ATTR, NULL); privacy statement. I am compiling this program in linux gcc compiler.. Where does this (supposedly) Gibson quote come from? Asking for help, clarification, or responding to other answers. "because the type "int" supports only -32768 ~ 32768" This is not true for any modern desktop or mobile OS or any OS that is targeted by cocos2d-x. And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. If the destination type is bool, this is a boolean conversion (see below). But gcc always give me a warning, that i cannot cast an int to a void*. Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. this way you won't get any warning. 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. 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. Projects. In such a case the programmer can use a void pointer to point to the location of the unknown data type. On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. Thanks for contributing an answer to Stack Overflow! 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:5658:9: note: expanded from macro 'SCAN_END_SINGLE' Floating-point conversions What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. So you know you can cast it back like this. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. 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. The preprocessor will replace your code by this: This is unlikely what you are trying to do. 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. 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; rev2023.3.3.43278. byte -> short -> char -> int -> long -> float -> double. You can fix this error by replacing this line of code. Create an account to follow your favorite communities and start taking part in conversations. Pull requests. Or, they are all wrong. (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. What video game is Charlie playing in Poker Face S01E07? What happens if you typecast as unsigned first? Asking for help, clarification, or responding to other answers. Thanks for contributing an answer to Stack Overflow! static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). We have to pass address of the variable to the function because in function definition argument is pointer variable. The text was updated successfully, but these errors were encountered: You signed in with another tab or window. From the question I presume the OP does. casting from int to void* and back to int. The difference between a and &a is the type. how to cascade 2d int array to 2d void pointer array? If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. How Intuit democratizes AI development across teams through reusability. I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. It is done by the compiler on its own, without any external trigger from the user. Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. I don't see how anything bad can happen . Don't do that. Visit Microsoft Q&A to post new questions. C/C++ , Cerror: cast to 'void *' from smaller integer type 'int'. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. The program can be set in such a way to ask the user to inform the type of data and . 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. rev2023.3.3.43278. Mutually exclusive execution using std::atomic? 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. Find centralized, trusted content and collaborate around the technologies you use most. that any valid pointer to void can be converted to this type, then You are correct, but cocos actually only uses that address as a unique id. STR34-C. Bulk update symbol size units from mm to map units in rule-based symbology. 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. You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : There is absolutely not gurantee that sizeof(int) <= sizeof(void*). 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. Asking for help, clarification, or responding to other answers. I would create a structure and pass that as void* to pthread_create. Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. Asking for help, clarification, or responding to other answers. It is purely a compile-time directive which instructs the compiler to treat expression as if it had . This returns the first 32 bits of the pointer which may be the top or the bottom depending on big versus little endian, as comment #2 said. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. What is the point of Thrower's Bandolier? SCAN_PUT(ATTR, NULL); Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. For example, the main thread could wait for all of the other threads to end before terminating. You may declare a const int variable and cast its reference to the void*. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. unsigned long call_fn = (unsigned long)FUNC; AC Op-amp integrator with DC Gain Control in LTspice. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Otherwise, if the original pointer value points to an object a, and there is an object b of the . 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". Connect and share knowledge within a single location that is structured and easy to search. A nit: in your version, the cast to void * is unnecessary. See also this documentation.. From and Into are generally intended to be lossless, infalliable conversions.as on the other hand can discard data and lead to bugs in some situations, for example casting a u64 to a usize may truncate the value on a 32-bit host. *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 . To learn more, see our tips on writing great answers. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. B language was designed to develop . I'm trying to create a void* from an int. There exist two main syntaxes for generic type-casting: functional and c-like: 1 2 3 4 double x = 10.3; int y; y = int (x); // functional notation y = (int) x; // c-like cast notation The functionality of these generic forms of type-casting is enough for most needs with fundamental data types. 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. You use the address-of operator & to do that. BUT converting a pointer to void* and back again is well supported (everywhere). I'm only guessing here, but I think what you are supposed to do is actually pass the address of the variable to the function. Why do small African island nations perform better than African continental nations, considering democracy and human development? If the function had the correct signature you would not need to cast it explicitly. 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. What does casting to void* does when passing arguments to variadic functions? Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. Thank you all for your feedback. If you cast an int pointer int, you might get back a different integer. "clang" "-Ilib\libopenvswitch.a.p" "-Ilib" "-I..\lib" "-I." Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? 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 The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. That's not a good idea if the original object (that was cast to void*) was an integer. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). This page was last modified on 12 February 2023, at 18:25. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ property that any valid pointer to void can be converted to this type, I cannot reverse my upvote of user384706's answer, but it's wrong. (void *)i Error: cast to 'void *' from smaller integer type 'int' PS: UBUNTUCLANG3.5 clang -O0 -std=gnu11 -march=native -lm -lpthread pagerank.c -o pagerank c pthreads 4 10.3k 2 21 2015-06-05 But I'm nitpicking .. 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. Fork 63. If any, how can the original function works without errors if we just ignore the warning. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. 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" (. Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. @Martin York: No, it doesn't depend on endiannness. Connect and share knowledge within a single location that is structured and easy to search. If you need to keep the returned address, just keep it as void*. Before I update Xcode, my project still can build and run normally with all devices. Error while setting app icon and launch image in xcode 5.1. void* -> integer -> void* rather than integer -> void* -> integer. You need to pass an actual pointer. Returns a value of type new-type. 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. 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. If the value is ever used as pointer again that will prove to be an extremely bad idea. 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. For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. eg. Not the answer you're looking for? Why is there a voltage on my HDMI and coaxial cables? 10) A prvalue of type pointer to void (possibly cv-qualified) can be converted to pointer to any object type. 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. Don't do that. 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. Not the answer you're looking for? How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. Already on GitHub? 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. 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)). Safe downcast may be done with dynamic_cast. Bulk update symbol size units from mm to map units in rule-based symbology. // OK: lvalue denoting the original d object, // UB: the b subobject is not a base class subobject, // 6. array-to-pointer followed by upcast, https://en.cppreference.com/mwiki/index.php?title=cpp/language/static_cast&oldid=147983, when converting a 'pointer to object' to 'pointer to, the conversion from floating-point values, the conversion from bit-fields to rvalue references, the conversion from integral or enumeration values to enumeration, the conversion from integral or enumeration values to, the conversion from a member of base class type to, a standard-layout class object with no data members, a non-standard-layout union object and a non-static data, for base-to-derived pointer conversions and, the conversion to enumeration types with fixed underlying type, a standard-layout class might have a non-pointer-interconvertible, If the underlying type is not fixed, the behavior is undefined if the value of, If the underlying type is fixed, the result is the same as, one is a union object and the other is a non-static data member of that object, or. 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. Keep in mind that thrArg should exist till the myFcn() uses it. what does it mean to convert int to void* or vice versa? Making statements based on opinion; back them up with references or personal experience. An open (void) pointer can hold a pointer of any type. 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;. Disconnect between goals and daily tasksIs it me, or the industry? Casting arguments inside the function is a lot safer. You can only do this if you use a synchronization primitive to ensure that there is no race condition. How to correctly cast a pointer to int in a 64-bit application? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. The main point is: a pointer has a platform dependent size. The subreddit for the C programming language, Press J to jump to the feed. Thanks for contributing an answer to Stack Overflow! I am an entry level C programmer. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? @Shahbaz you could but I will not suggest to a C newbie to use globals. Connect and share knowledge within a single location that is structured and easy to search. Identify those arcade games from a 1983 Brazilian music video. Can I tell police to wait and call a lawyer when served with a search warrant? ^~~~~~~~~~~~~~~~~~~~ How Intuit democratizes AI development across teams through reusability. This is why you got Error 1 C2036, from your post. I have a two functions, one that returns an int, and one that takes a const void* as an argument. 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). The proper way is to cast it to another pointer type. What is the purpose of non-series Shimano components? ../lib/odp-util.c:5601:9: note: expanded from macro 'SCAN_PUT' 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. To learn more, see our tips on writing great answers. To avoid truncating your pointer, cast it to a type of identical size. pthread passes the argument as a void*. Converting one datatype into another is known as type casting or, type-conversion. It is easier to understand and write than any other assembly language. 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. B programing language is a language based on basic combined programming or a BCPL, and it is the precursor of the C programming language. rev2023.3.3.43278. I'm trying to learn pthreads and thing that keeps bugging me is how do i really pass argument to the function. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? And, most of these will not even work on gcc4. It solved my problem too. You could use this code, and it would do the same thing as casting ptr to (char*). } SCAN_END_SINGLE(ATTR) I have looked around and can't seem to find any information on how to do this. return ((void **) returnPtr);} /* Matrix() */. The int data type is the primary integer data type in SQL Server. Put your define inside a bracket: without a problem. If int is no larger than pointer to void then one way to store the value is by simply copying the bytes: int i . How to notate a grace note at the start of a bar with lilypond? you can just change architecture to support 32 bit compilation by all below in in Build Settings. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Does Counterspell prevent from any further spells being cast on a given turn? 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. Your first example is risky because you have to be very careful about the object lifetimes. 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. error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't.
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