They should do their job unless your code is too tricky. . Casting a pointer to void* and back is valid use of reinterpret_cast<>. You can use any other pointer, or you can use (size_t), which is 64 bits. Don't do that.
This is not a conversion at all. Many errors come from warnings. 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. How to convert a factor to integer\numeric without loss of information? this way I convert an int to a void* which is much better than converting a void* to an int. For example, (double) 1/3 will give a double result instead of an int one. Based on the design of this function, which modification is right. I want to learn the difference between the three type cast operators: Hi, Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, I would try to fix the code instead. If the result lies outside the range of representable values by the type, the conversion causes, Otherwise, if the conversion is between numeric types of the same kind (integer-to-integer or floating-to-floating), the conversion is valid, but the value is. The Test method has an Animal parameter, thus explicitly casting the argument a to a Reptile makes a dangerous assumption. I saw on a couple of recent posts people saying that casting the return Not the answer you're looking for? For example, a variable of type long (64-bit integer) can store any value that an int (32-bit integer) can store. Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. Question is, how do I explain this to Clang? Needless to say, this will still be wrong. Asking for help, clarification, or responding to other answers. Is a downhill scooter lighter than a downhill MTB with same performance? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. I've always been a little sketchy on the differences between static, You might want to typedef, You should change your code to handle this. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. Can my creature spell be countered if I cast a split second spell after it? Canadian of Polish descent travel to Poland with Canadian passport. */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j;
Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? User without create permission can create a custom object from Managed package using Custom Rest API. for saving RAM), use union, and make sure, if the mem address is treated as an int only if you know it was last set as an int. It is commonly called a pointer to T and its type is T*. A boy can regenerate, so demons eat him for years. There's no proper way to cast this to int in general case. Casting arguments inside the function is a lot safer. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. rev2023.5.1.43405. The proper way is to cast it to another pointer type. Did the drapes in old theatres actually say "ASBESTOS" on them? For example, the string cannot be implicitly converted to int. Visit Microsoft Q&A to post new questions. C / C++ Forums on Bytes. Can anybody explain how to pass an integer to a function which receives (void * ) as a parameter? What is this brick with a round back and a stud on the side used for. For more information, see How to safely cast using pattern matching and the as and is operators. To learn more, see our tips on writing great answers. To avoid truncating your pointer, cast it to a type of identical size. Asking for help, clarification, or responding to other answers. Making statements based on opinion; back them up with references or personal experience. struct foo *foo; u8 -> u32) will zero-extend if the source is unsigned sign-extend if the source is signed Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul (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, , i Should I re-do this cinched PEX connection? Please help me with the right way to convert void* to int in c++ Mar 30, 2020 at 10:44am George P (5286) Maybe try reinterpret_cast? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Which ability is most related to insanity: Wisdom, Charisma, Constitution, or Intelligence? For some type X he has: Two MacBook Pro with same model number (A1286) but different year. Thanks for contributing an answer to Stack Overflow! What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. A good thing in general, but if you want to disable the warning, just do it. The preprocesor absolutely will not perform arithmetic. I hit this same problem in a project without C++11, and worked around it like this: Thanks for contributing an answer to Stack Overflow! I am looking to clean up the For example, assigning an int value to a long variable. rev2023.3.3.43278. cwindowccwindowsword[3]={"ab"};_ab charPersondebug, A, A, , "C" ???? This is a fine way to pass integers to new pthreads, if that is what you need. The most general answer is - in no way. Converting a void* to an int is non-portable way that may work or may not! 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. The semantics of numeric casts are: Casting between two integers of the same size (e.g. for (i=0, j=0; j works only in b/w ! What is the difference between const int*, const int * const, and int const *? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. or, Array with multiple data types? Is there any known 80-bit collision attack? @Martin York: No, it doesn't depend on endiannness. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Use returnPtr[j] = (void *) ((long)ptr + i); ). You can also convert values from one type to another explicitly using the cast operator (see Chapter 5 ): ( type_name) expression In the following example, the cast operator causes the division of one integer variable by another to be performed as a floating-point operation: int sum = 22, count = 5; double mean = (double)sum / count; 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. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, xcode build error: Semantic issue cast from pointer to smaller type 'int' loses information. Casting int to void* loses precision, and what is the solution in required cases, c++: cast from "const variable*" to "uint32" loses precision, cast from 'char*' to 'int' loses precision. @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. For a complete list of supported explicit numeric conversions, see the Explicit numeric conversions section of the Built-in numeric conversions article. This is flat out wrong. i Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. pcs leave before deros; chris banchero brother; tc dimension custom barrels; cast void pointer to char array. Generating points along line with specifying the origin of point generation in QGIS. I don't understand why the following two cases produce different Hi, I've this question: suppose we have two differently typed pointers: 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). Save this piece of code as mycast.hpp and add -include mycast.hpp to your Makefile. There is absolutely not gurantee that sizeof(int) <= sizeof(void*). Join Bytes to post your question to a community of 472,246 software developers and data experts. The compiler is perfectly correct & accurate! Can I use my Coinbase address to receive bitcoin? Convert integers, floating-point values and enum types to enum types. rev2023.5.1.43405. 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. This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s). This forum has migrated to Microsoft Q&A. dynamic, and reinterpret casting. For integral types, this means the range of the source type is a proper subset of the range for the target type. 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. cast to void *' from smaller integer type 'int cast to void *' from smaller integer type 'int. rev2023.5.1.43405. How to get the error message from the error code returned by GetLastError()? Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? How to cast a void pointer to any other type in C || #C Programming language || Coding is Life 487 03 : 37 Unable to cast object of type 'System DateTime' to type 'System String' SharpCoder 336 10 : 53 Tkinter window geometry to manage height width and zoom out using state and resizable () option plus2net 107 Author by david.brazdil 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. @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. In 64-bit programs, the size of the pointer is 64 bits and it cannot be put into the int type that remains 32-bit almost in all the systems. 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. 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;. it often does reinterpret_cast<uint32_t> (ptr). If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. how to cascade 2d int array to 2d void pointer array? Find centralized, trusted content and collaborate around the technologies you use most. Or you might need to assign a class variable to a variable of an interface type. Why does setupterm terminate the program? I have a question about casting a function pointer. this question. You can use any other pointer, or you can use (size_t), which is 64 bits. There's no proper way to cast this to int in general case. linux c-pthreads: problem with local variables. How do I check if a string represents a number (float or int)? But gcc always give me a warning, that i cannot cast an int to a void*. It seems both static_cast and dynamic_cast can cast a base class How to cast/convert pointer to reference in C++, clang error: unknown argument: '-mno-fused-madd' (python package installation failure). Integer conversions, both implicit and explicit (using a cast), must be guaranteed not to result in lost or misinterpreted data. Find centralized, trusted content and collaborate around the technologies you use most. C99 defines the types "intptr_t" and "uintptr_t" which do . I'm trying to create a void* from an int. Solution 1. I agree passing a dynamically allocated pointer is fine (and I think the best way). Interpreting non-statistically significant results: Do we have "no evidence" or "insufficient evidence" to reject the null? MIP Model with relaxed integer constraints takes longer to solve than normal model, why? The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. Basically its a better version of (void *)i. How can I control PNP and NPN transistors together from one pin? Why are players required to record the moves in World Championship Classical games? I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. pthread passes the argument as a void*. As a result, it is possible to silently convert from one pointer type to another without the compiler diagnosing the problem by storing or casting a pointer to void * and then storing or casting it to the final type. Asking for help, clarification, or responding to other answers. 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. Which was the first Sci-Fi story to predict obnoxious "robo calls"? 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. What I am trying to emphasis that conversion from int to pointer and back again can be frough with problems as you move from platform to platform. We have to pass address of the variable to the function because in function definition argument is pointer variable. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. Storage management is an important module of database, which can be subdivided into memory management and external memory management. I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. Not the answer you're looking for? LLNL's tutorial is bad and they should feel bad. Is "I didn't think it was serious" usually a good defence against "duty to rescue"? Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. C++ how to get the address stored in a void pointer? How create a simple program using threads in C? If your standard library (even if it is not C99) happens to provide these types - use them. Please start a new discussion. converted back to pointer to void, and the result will compare equal So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. Wrong. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. Yeah, the tutorial is doing it wrong. MIP Model with relaxed integer constraints takes longer to solve than normal model, why? Infact I know several systems where that does not hold. If you need to keep the returned address, just keep it as void*. 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. Casting is required when information might be lost in the conversion, or when the conversion might not succeed for other reasons. Your strategy will not work for stack-allocated objects, be careful!! C# provides the is operator to enable you to test for compatibility before actually performing a cast. 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. What differentiates living as mere roommates from living in a marriage-like relationship? Short story about swapping bodies as a job; the person who hires the main character misuses his body. How to find the size of an array (from a pointer pointing to the first element array)? 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. 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. That could create all kinds of trouble. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. Is it safe to publish research papers in cooperation with Russian academics? 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. Widening or Automatic Type Conversion If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. 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. I would create a structure and pass that as void* to pthread_create. As shown in the following example, a type cast that fails at run time will cause an InvalidCastException to be thrown. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. It keeps throwing this exact error message even though both types are 32 bits wide. OP said he doesn't want it. What is this brick with a round back and a stud on the side used for? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. I'll edit accordingly. Explanation Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility .
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