SCAN_PUT(ATTR, NULL); I would create a structure and pass that as void* to pthread_create. Connect and share knowledge within a single location that is structured and easy to search. reinterpret_cast is a type of casting operator used in C++. 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. Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. What does casting to void* does when passing arguments to variadic functions? ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' Just edited. @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? 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" (. Terrible solution. Press question mark to learn the rest of the keyboard shortcuts. ", "? @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. 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]. However, you are also casting the result of this operation to (void*). Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. Why do small African island nations perform better than African continental nations, considering democracy and human development? Notifications. C/C++ , Cerror: cast to 'void *' from smaller integer type 'int'. This is an old C callback mechanism so you can't change that. How to get the error message from the error code returned by GetLastError()? A nit: in your version, the cast to void * is unnecessary. I think the solution 3> should be the correct one. From what I read about casting in the C11 standard, my feeling is, that it is arguable to emit a warning on an explicit conversion. } SCAN_END_SINGLE(ATTR) You should perform type conversion based on 64bit build system because the type "int" supports only -32768 ~ 32768. 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. 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. cast to 'void *' from smaller integer type 'int' But the problem has still happened. [that could be a TODO - not to delay solving the ICE]. @jackdoe: It's a waste of human life to write code that "you may need in the future". Implementing From will result in the Into implementation but not vice-versa. "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. 4. Type Conversions - C in a Nutshell [Book] - O'Reilly Online Learning ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' Don't pass your int as a void*, pass a int* to your int, so you can cast the void* to an int* and copy the dereferenced pointer to your int. You can convert the values from one type to another explicitly using the cast operator as follows (type_name) expression You need to pass an actual pointer. This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). (void *)i Error: cast to 'void *' from smaller integer type 'int'. 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). To learn more, see our tips on writing great answers. If you need to keep the returned address, just keep it as void*. Create an account to follow your favorite communities and start taking part in conversations. How to use Slater Type Orbitals as a basis functions in matrix method correctly? 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. C99 defines the types "intptr_t" and "uintptr_t" which do . 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;. What you do here is undefined behavior, and undefined behavior of very practical sort. On all of them int is 32bit, not 16bit. On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. [] ExplanatioUnlike static_cast, but like const_cast, the reinterpret_cast expression does not compile to any CPU instructions (except when converting between integers and pointers or on obscure architectures where pointer representation depends on its type). Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. Not the answer you're looking for? There is no "correct" way to store a 64-bit pointer in an 32-bit integer. INT31-C. Ensure that integer conversions do not result in lost or There's no proper way to cast this to int in general case. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. 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. Once you manage to make this cast, then what?! with ids being an array of ints and touch being a pointer. But this code pass the normal variable .. @Martin York: No, it doesn't depend on endiannness. 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. static_cast on the other hand should deny your stripping away the const qualifier. If this is the data to a thread procedure, then you quite commonly want to pass by value. Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). casting from int to void* and back to int. How to correctly cast a pointer to int in a 64-bit application? I have a two functions, one that returns an int, and one that takes a const void* as an argument. I'm using cocos2d-x-2.2.2. 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. for (i=0, j=0; jCasting type int to const void* - C / C++ 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. Whats the grammar of "For those whose stories they are"? Thanks for contributing an answer to Stack Overflow! Java Type Casting. Based on the design of this function, which modification is right. property that any valid pointer to void can be converted to this type, What is the difference between const int*, const int * const, and int const *? The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. The correct answer is, if one does not mind losing data precision. Casting a pointer to void* and back is valid use of reinterpret_cast<>. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? In such a case the programmer can use a void pointer to point to the location of the unknown data type. If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. Casting type void to uint8_t - Arduino Forum It's always a good practice to put your #define's in brackets to avoid such surprise. Visit Microsoft Q&A to post new questions. What is the point of Thrower's Bandolier? 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. 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. You can use any other pointer, or you can use (size_t), which is 64 bits. 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). What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. Mutually exclusive execution using std::atomic? Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. If the function had the correct signature you would not need to cast it explicitly. . Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? The following program casts a double to an int. The problem just occur with Xcode 5.1. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. You may declare a const int variable and cast its reference to the void*. Or, they are all wrong. (i.e. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. byte -> short -> char -> int -> long -> float -> double. Error while setting app icon and launch image in xcode 5.1. @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. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. "I think what you should do is actually pass the address of the variable to the function" Not necessarily. The mapping in pointer<->integer casts is implementation defined, but the intent was that if the pointer type is large enough and isn't forcefully aligned (, But that's different. A nit: in your version, the cast to void * is unnecessary. Implementation-dependent. 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. 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. ), For those who are interested. Thanks for pointing that out. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. For the Nozomi from Shinagawa to Osaka, say on a Saturday afternoon, would tickets/seats typically be available - or would you need to book? You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. 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 It's an int type guaranteed to be big enough to contain a pointer. The following behavior-changing defect reports were applied retroactively to previously published C++ standards. rev2023.3.3.43278. Why is there a voltage on my HDMI and coaxial cables? Getting Command /bin/sh failed with exit code 65 Error with Xcode 5.1 . a cast of which the programmer should be aware of what (s)he is doing. Thanks for contributing an answer to Stack Overflow! However the actual code in question contains an explicit c-style cast to int. Usually that means the pointer is allocated with. 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. For integer casts in specific, using into() signals that . @DavidHeffernan I rephrased that sentence a little. 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. What does it mean to convert int to void* or vice versa? How do I set, clear, and toggle a single bit? iphone - Error "Cast from pointer to smaller type 'int' loses Put your define inside a bracket: without a problem. Pull requests. reinterpret_cast conversion - cppreference.com Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. (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 Remembering to delete the pointer after use so that we don't leak. Remarks. 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). If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. In the case of Widening Type Casting, the lower data type (having smaller size) is converted into the higher data type (having larger size). From that point on, you are dealing with 32 bits. Acidity of alcohols and basicity of amines. In C (int)b is called an explicit conversion, i.e. Are there tables of wastage rates for different fruit and veg? This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. Asking for help, clarification, or responding to other answers. The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. The difference between the phonemes /p/ and /b/ in Japanese. We have to pass address of the variable to the function because in function definition argument is pointer variable. SCAN_PUT_ATTR(mask, ATTR, smask, FUNC); Casting int to void* : r/C_Programming - reddit 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. And, most of these will not even work on gcc4. The cast back to int * is not, though. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). casting from int to void* and back to int - C / C++ 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. Sign in And in this context, it is very very very common to see programmers lazily type cast the. 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. ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' How to convert a factor to integer\numeric without loss of information? Can I tell police to wait and call a lawyer when served with a search warrant? C - Type Casting - tutorialspoint.com I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. 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. [Solved] Properly casting a `void*` to an integer in C++ STR34-C. Cast characters to unsigned char before converting to larger Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. That's not a good idea if the original object (that was cast to void*) was an integer. If you cast an int pointer int, you might get back a different integer. I assumed that gcc makes a 65536 out of my define, but I was wrong. 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). and how to print the thread id of 2d array argument? Asking for help, clarification, or responding to other answers. 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. -1, Uggh. Yeah, the tutorial is doing it wrong. Returns a value of type new-type. What is the purpose of non-series Shimano components? But I don't want to edit code in "EAGLView.mm" because it's a "library file". Converting one datatype into another is known as type casting or, type-conversion. this way you won't get any warning. This page was last modified on 12 February 2023, at 18:25. When is casting void pointer needed in C? 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. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? Connect and share knowledge within a single location that is structured and easy to search. C++ Tutorial => Conversion between pointer and integer 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. Asking for help, clarification, or responding to other answers. SCAN_PUT_ATTR(key, ATTR, skey, FUNC); that any valid pointer to void can be converted to this type, then However even though their types are different, the address is going to be the same. To avoid truncating your pointer, cast it to a type of identical size. You are correct, but cocos actually only uses that address as a unique id. 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. Can Martian regolith be easily melted with microwaves? Safe downcast may be done with dynamic_cast. Cast a smaller integer to a larger integer - community - The Rust Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. To learn more, see our tips on writing great answers. Now, what happens when I run it with the thread sanitizer? The result is the same as implicit conversion from the enum's underlying type to the destination type. And then assign it to the double variable. You can only do this if you use a synchronization primitive to ensure that there is no race condition. "clang" "-Ilib\libopenvswitch.a.p" "-Ilib" "-I..\lib" "-I." even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. Issues. AC Op-amp integrator with DC Gain Control in LTspice. Use of Void pointers in C programming language Type conversions - cplusplus.com If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. This is not even remotely "the correct answer". My code is all over the place now but I appreciate you all helping me on my journey to mastery! Recovering from a blunder I made while emailing a professor. ^~~~~~~~~~~~~~~~~~~~~ RNINGS" "-D_CRT_SECURE_NO_DEPRECATE" -MD -MQ lib/libopenvswitch.a.p/odp-util.c.obj -MF "lib\libopenvswitch.a.p\odp-util.c.obj.d" -o lib/libopenvswitch.a.p/od

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