cast to void *' from smaller integer type 'int cast to void *' from smaller integer type 'int

Type casting is when you assign a value of one primitive data type to another type. Does a summoned creature play immediately after being summoned by a ready action? The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. I have looked around and can't seem to find any information on how to do this. To access the object value, use the * dereference operator: int * p; assert (p == null ); p = new int (5); assert (p != null ); assert (*p == 5); (*p)++; assert (*p == 6); If a pointer contains a null value, it is not pointing to a valid object. Once you manage to make this cast, then what?! ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' a cast of which the programmer should be aware of what (s)he is doing. In the first example, the variable c1 of the char type is converted to a temporary variable of the int type, because the second operand in the division operation, the constant 2, is of the higher type int. @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. this way you won't get any warning. 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. lexborisov Modest Public. You can use any other pointer, or you can use (size_t), which is 64 bits. What does it mean to convert int to void* or vice versa? @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. 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. this question. Here is my code: I already tried (void*)M_TABLE_SIZE but then I get an error that I cannot use the * operator. The problem is not with casting, but with the target type loosing half of the pointer. Most answers just try to extract 32 useless bits out of the argument. It's always a good practice to put your #define's in brackets to avoid such surprise. The value of float variable is= 37.75. 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. Making statements based on opinion; back them up with references or personal experience. So you know you can cast it back like this. Windows has 32 bit long only on 64 bit as well. to the original pointer: The following type designates an unsigned integer type with the If the value is ever used as pointer again that will prove to be an extremely bad idea. The main point is: a pointer has a platform dependent size. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Thank you all for your feedback. Create an account to follow your favorite communities and start taking part in conversations. 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. The cast back to int * is not, though. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); unsigned long call_fn = (unsigned long)FUNC; ^~~~~~~~~~~~~~~~~~~~~ There's no proper way to cast this to int in general case. What is the point of Thrower's Bandolier? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. 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 are getting warnings due to casting a void* to a type of a different size. The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. And, most of these will not even work on gcc4. ^~~~~~~~~~~~~~~~~~~~ Identify those arcade games from a 1983 Brazilian music video. [that could be a TODO - not to delay solving the ICE]. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. Implementing From will result in the Into implementation but not vice-versa. 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. This is not even remotely "the correct answer". byte -> short -> char -> int -> long -> float -> double. The text was updated successfully, but these errors were encountered: 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. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The difference between the phonemes /p/ and /b/ in Japanese. Thanks for contributing an answer to Stack Overflow! If the destination type is bool, this is a boolean conversion (see below). Casting arguments inside the function is a lot safer. How create a simple program using threads in C? If you preorder a special airline meal (e.g. Do new devs get fired if they can't solve a certain bug? 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. 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". You are correct, but cocos actually only uses that address as a unique id. Connect and share knowledge within a single location that is structured and easy to search. 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. Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. Don't do that. This is why you got Error 1 C2036, from your post. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. Not the answer you're looking for? 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. How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? 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. Such pointers can be stored in 32-bit data types (for instance, int, DWORD). Already on GitHub? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. this way I convert an int to a void* which is much better than converting a void* to an int. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Now, what happens when I run it with the thread sanitizer? Find centralized, trusted content and collaborate around the technologies you use most. This answer is incorrect for the reasons that have already been mentioned in the comment of, Error "Cast from pointer to smaller type 'int' loses information" in EAGLView.mm when update Xcode to 5.1 (5B130a), http://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models, http://stackoverflow.com/questions/18913906/xcode-5-and-ios-7-architecture-and-valid-architectures, How Intuit democratizes AI development across teams through reusability. But I'm nitpicking .. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. 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 To learn more, see our tips on writing great answers. Converting a void* to an int is non-portable way that may work or may not! The result is the same as implicit conversion from the enum's underlying type to the destination type. What is the purpose of non-series Shimano components? Next, when doing pointer arithmetic, the addition operation will use the pointer's type to determine how many bytes to add to it when incrementing it. Why does flowing off the end of a non-void function without returning a value not produce a compiler error? The correct answer is, if one does not mind losing data precision. I wish that you write those answer first than the explanation. Implicit Type Conversion is also known as 'automatic type conversion'. Before I update Xcode, my project still can build and run normally with all devices. SCAN_PUT_ATTR(key, ATTR, skey, FUNC); rev2023.3.3.43278. you can just change architecture to support 32 bit compilation by all below in in Build Settings. Using Kolmogorov complexity to measure difficulty of problems? Therefore, you need to change it to long long instead of long in windows for 64 bits. How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. But then you need to cast your arguments inside your thread function which is quite unsafe cf. *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 . rev2023.3.3.43278. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. vegan) just to try it, does this inconvenience the caterers and staff? p-util.c.obj "-c" ../lib/odp-util.c If you preorder a special airline meal (e.g. Any help with this is appreciated. */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. If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? XCode 5.1 is change all architecture to 64 bit. STR34-C. 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). You may declare a const int variable and cast its reference to the void*. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Otherwise, if the original pointer value points to an object a, and there is an object b of the . Find centralized, trusted content and collaborate around the technologies you use most. 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. Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. ^~~~~~~~~~~~~~~~~~~ I assumed that gcc makes a 65536 out of my define, but I was wrong. 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). C99 defines the types "intptr_t" and "uintptr_t" which do . The preprocessor will replace your code by this: This is unlikely what you are trying to do. Replacing broken pins/legs on a DIP IC package, AC Op-amp integrator with DC Gain Control in LTspice. Can Martian regolith be easily melted with microwaves? Yeah, the tutorial is doing it wrong. GitHub. To learn more, see our tips on writing great answers. Then i can continue compiling. Projects. with ids being an array of ints and touch being a pointer. rev2023.3.3.43278. Instead of using a long cast, you should cast to size_t. windows meson: cast to smaller integer type 'unsigned long' from 'void *'. 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. @DietrichEpp can you explain what is race condition with using. 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. static_cast on the other hand should deny your stripping away the const qualifier. That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. Bulk update symbol size units from mm to map units in rule-based symbology. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. I need to cast the int from the first function so that I can use it as an argument for the second function. However even though their types are different, the address is going to be the same. Connect and share knowledge within a single location that is structured and easy to search. @Shahbaz you could but I will not suggest to a C newbie to use globals. It is purely a compile-time directive which instructs the compiler to treat expression as if it had . Safe downcast may be done with dynamic_cast. LLNL's tutorial is bad and they should feel bad. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Can I tell police to wait and call a lawyer when served with a search warrant? ", "!"? . The problem was there before, you just are being notified of it. Hence there is no loss in data. This is known as implicit type casting or type promotion, compiler automatically converts smaller data type to larger data type. 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. Just re-enforcing the old behavior of Xcode 5.0 and earlier versions, that already cut away parts of the address by casting it to int, won't introduce any new bugs and avoids the need to learn and understand lots of implementation-internal cocos code. Therefore it is perfectly valid for the compiler to throw an error for a line like. In my case, I was using a 32-bit value that needed to be passed to an OpenGL function as a void * representing an offset into a buffer. rev2023.3.3.43278. This page has been accessed 1,655,678 times. Thanks for contributing an answer to Stack Overflow! reinterpret_cast<void *>(42)). equal to the original pointer: First you are using a define, which is not a variable. what does it mean to convert int to void* or vice versa? Have a question about this project? 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). 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. No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : I'm trying to learn pthreads and thing that keeps bugging me is how do i really pass argument to the function. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. When is casting void pointer needed in C? This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. If the function had the correct signature you would not need to cast it explicitly. // 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. privacy statement. Using Kolmogorov complexity to measure difficulty of problems? C / C++ Forums on Bytes. Connect and share knowledge within a single location that is structured and easy to search. use $(ARCHS_STANDARD_32_BIT) at Architecture instead of $(ARCHS_STANDARD). 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. 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. Bulk update symbol size units from mm to map units in rule-based symbology. how to cascade 2d int array to 2d void pointer array? I am an entry level C programmer. vegan) just to try it, does this inconvenience the caterers and staff? If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. Implementation-dependent. The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. Click to see the query in the CodeQL repository. Here, the Java first converts the int type data into the double type. SCAN_PUT(ATTR, NULL); pthread passes the argument as a void*. There is no "correct" way to store a 64-bit pointer in an 32-bit integer. How to use Slater Type Orbitals as a basis functions in matrix method correctly? ), For those who are interested. Find centralized, trusted content and collaborate around the technologies you use most. Disconnect between goals and daily tasksIs it me, or the industry? You need to pass an actual pointer. 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. 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. 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. Why did Ukraine abstain from the UNHRC vote on China? If your standard library (even if it is not C99) happens to provide these types - use them. 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. Since all pointers on 64-bit Windows are 64 bits, you are growing the data size from 32 bits backto 64 bits. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' casting from int to void* and back to int. A cast specifies a conversion from one type to another. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Setting a buffer of char* with intermediate casting to int*. 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. 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. @BlueMoon Thanks a lot! An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. Yesterday, I updated Xcode to the newest version (5.1 (5B130a)) to compatible with iOS 7.1. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini 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. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. 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 Asking for help, clarification, or responding to other answers. (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. If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. Put your define inside a bracket: without a problem. This is an old C callback mechanism so you can't change that. Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. whether it was an actual problem is a different matter though. While working with Threads in C, I'm facing the warning, "warning: cast to pointer from integer of different size". Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). 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.