There is no "correct" way to store a 64-bit pointer in an 32-bit integer. @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Find centralized, trusted content and collaborate around the technologies you use most. Keep in mind that thrArg should exist till the myFcn() uses it. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Projects. Thanks for contributing an answer to Stack Overflow! 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. What is the purpose of non-series Shimano components? An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. 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. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] The difference between the phonemes /p/ and /b/ in Japanese. The following behavior-changing defect reports were applied retroactively to previously published C++ standards. @jackdoe: It's a waste of human life to write code that "you may need in the future". For example, the main thread could wait for all of the other threads to end before terminating. Narrowing Casting (manually) - converting a larger type to a . You think by casting it here that you are avoiding the problem! All float types are to be converted to double. vegan) just to try it, does this inconvenience the caterers and staff? Why is there a voltage on my HDMI and coaxial cables? Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? 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. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. (void *)i Error: cast to 'void *' from smaller integer type 'int'. c - Cast int to void* - Stack Overflow ", "!"? In the best case this will give the same results as the original code, with no advantages, but in the worst case it will fail in multiple catastrophic ways (type punning, endianness, less efficient, etc. You are getting warnings due to casting a void* to a type of a different size. You can use any other pointer, or you can use (size_t), which is 64 bits. @DietrichEpp can you explain what is race condition with using. The subreddit for the C programming language, Press J to jump to the feed. static_cast conversion - cppreference.com 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. 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. But then you need to cast your arguments inside your thread function which is quite unsafe cf. How to use Slater Type Orbitals as a basis functions in matrix method correctly? 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 So make sure you understand what you are doing! Connect and share knowledge within a single location that is structured and easy to search. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. (i.e. 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. Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. There's no proper way to cast this to int in general case. The only alternative is really to take time and fix all 64-bit code issues, of which there may be some non-trivial issues. Pull requests. 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. ", "? What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. to your account, [87/252] Compiling C object lib/libopenvswitch.a.p/odp-util.c.obj Why did Ukraine abstain from the UNHRC vote on China? I assumed that gcc makes a 65536 out of my define, but I was wrong. And when assigning to a void pointer, all type information is lost. sound/soc/codecs/tlv320aic32x4.c:1202:18: warning: cast to smaller Just edited. Find centralized, trusted content and collaborate around the technologies you use most. (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 Now, what happens when I run it with the thread sanitizer? This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. 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). I wish that you write those answer first than the explanation. warning C4311: 'type cast': pointer truncation from 'void *' to 'long' in ECPG test files. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. While working with Threads in C, I'm facing the warning, "warning: cast to pointer from integer of different size". This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). SQL Server does not automatically promote . My code is all over the place now but I appreciate you all helping me on my journey to mastery! It was derived from the BCPL, and the name of the b language is possibly from the BCPL contraction. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. 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. For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. @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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Implementing From will result in the Into implementation but not vice-versa. Asking for help, clarification, or responding to other answers. windows meson: cast to smaller integer type 'unsigned long' from 'void Does melting sea ices rises global sea level? Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. What I am saying is that it would be safer to use new(5) rather than 5 and deal with it appropriately at the other end. that any valid pointer to void can be converted to this type, then STR34-C. rev2023.3.3.43278. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. 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. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' The result is the same as implicit conversion from the enum's underlying type to the destination type. 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). Such pointers can be stored in 32-bit data types (for instance, int, DWORD). What is the point of Thrower's Bandolier? You can only do this if you use a synchronization primitive to ensure that there is no race condition. You may declare a const int variable and cast its reference to the void*. Well occasionally send you account related emails. Why is this sentence from The Great Gatsby grammatical? (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. This is known as implicit type casting or type promotion, compiler automatically converts smaller data type to larger data type. this way I convert an int to a void* which is much better than converting a void* to an int. Safe downcast may be done with dynamic_cast. @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. C99 defines the types "intptr_t" and "uintptr_t" which do . On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. for (i=0, j=0; jType Casting Of Pointers in C - Computer Notes 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. C - Type Casting - tutorialspoint.com To learn more, see our tips on writing great answers. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini Hence there is no loss in data. Create an account to follow your favorite communities and start taking part in conversations. You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : Thank you all for your feedback. 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. 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. Types - D Programming Language How do I set, clear, and toggle a single bit? Why is there a voltage on my HDMI and coaxial cables? 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. @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. Changing the type of ids would be the cleanest solution, but I decided against it when being confronted with this issue myself, as it only introduced a lot of issues with other code that is relying on ids being an int-array. casting from int to void* and back to int. Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul But assuming that it is, as long as the caller and the callee agree, you can do that sort of thing. How do I align things in the following tabular environment? So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. eg. The difference between a and &a is the type. ^~~~~~~~~~~~~~~~~~~~~ You are right! 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. Remembering to delete the pointer after use so that we don't leak. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' What video game is Charlie playing in Poker Face S01E07? The calculated expression consists of two operations. This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. And, most of these will not even work on gcc4. and how to print the thread id of 2d array argument? ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' Is it possible to create a concave light? windows meson: cast to smaller integer type 'unsigned long' from 'void *'. If the destination type is bool, this is a boolean conversion (see below). 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. 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.. 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. Returns a value of type new-type. Clang warnings for an invalid casting? - The FreeBSD Forums Visit Microsoft Q&A to post new questions. As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). There are ways to prevent this: pass a dynamic allocated argument if your not the passing thread is not static or if your argument is a local variable, otherwise there is no issue. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. No idea how it amassed 27 upvotes?! It is commonly called a pointer to T and its type is T*. Replacing broken pins/legs on a DIP IC package, AC Op-amp integrator with DC Gain Control in LTspice. For the Nozomi from Shinagawa to Osaka, say on a Saturday afternoon, would tickets/seats typically be available - or would you need to book? If any, how can the original function works without errors if we just ignore the warning. Note the difference between the type casting of a variable and type casting of a pointer. The value of float variable is= 37.75. How Intuit democratizes AI development across teams through reusability. Windows has 32 bit long only on 64 bit as well. 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. When is casting void pointer needed in C? Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? vegan) just to try it, does this inconvenience the caterers and staff? 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). Not the answer you're looking for? 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.