How to find the size of an array (from a pointer pointing to the first element array)? This is an old C callback mechanism so you can't change that. There are two occurences in "SemaCast.cpp" -- one of which suggests it's sensitive to MS extensions, https://github.com/llvm-mirror/clang/blob/release_50/lib/Sema/SemaCast.cpp#L2112 I don't see how anything bad can happen . 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;. " is pointer to interface, not interface" confusion, Cast from uint8_t pointer to uint32_t integer compilation error. 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. The semantics of numeric casts are: Casting between two integers of the same size (e.g. For a complete list of supported explicit numeric conversions, see the Explicit numeric conversions section of the Built-in numeric conversions article. For example, a variable of type long (64-bit integer) can store any value that an int (32-bit integer) can store. Question is, how do I explain this to Clang? If the function had the correct signature you would not need to cast it explicitly. Technically, these casts should therefore be valid. Basically its a better version of (void *)i. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Types - D Programming Language Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. Why don't we use the 7805 for car phone chargers? there How should an excellent flowchart be drawn? Can I use the spell Immovable Object to create a castle which floats above the clouds? ', referring to the nuclear power plant in Ignalina, mean? Not the answer you're looking for? C / C++ Forums on Bytes. Say I want to make It's always a good practice to put your #define's in brackets to avoid such surprise. rev2023.5.1.43405. For more information, see How to safely cast using pattern matching and the as and is operators. Casting and type conversions - C# Programming Guide It is possible for a cast operation that compiles correctly to fail at run time. Asking for help, clarification, or responding to other answers. Was Aristarchus the first to propose heliocentrism? MIP Model with relaxed integer constraints takes longer to solve than normal model, why? 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. Casting a pointer to void* and back is valid use of reinterpret_cast<>. Did the drapes in old theatres actually say "ASBESTOS" on them? You need to cast the void* pointer to a char* pointer - and then dereference that char* pointer to give you the char that it points to! Generating points along line with specifying the origin of point generation in QGIS. If your standard library (even if it is not C99) happens to provide these types - use them. They should do their job unless your code is too tricky. again. I saw on a couple of recent posts people saying that casting the return Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, I would try to fix the code instead. You need to pass an actual pointer. what does it mean to convert int to void* or vice versa? 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. void* -> integer -> void* rather than integer -> void* -> integer. Unfortunately, that hardware is 64-bit and the code contains many instances of pointer arithmetic that expects pointers to be 32-bit, i.e. What were the most popular text editors for MS-DOS in the 1980s? Why did DOS-based Windows require HIMEM.SYS to boot? Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul 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. @jackdoe: It's a waste of human life to write code that "you may need in the future". A nit: in your version, the cast to void * is unnecessary. EXP36-C. Do not cast pointers into more strictly aligned pointer types Embedded hyperlinks in a thesis or research paper. There is no "correct" way to store a 64-bit pointer in an 32-bit integer. Use #include to define it. It's not them. Type conversion in Java with Examples - GeeksforGeeks I need to execute a SQL Server stored procedure from Java/Spring, and the SP has a try/catch block that logs errors to a table. It is safer to not make assumptions, but rather check the type. arrays - I get the error: "cast to smaller integer type 'int' from is there such a thing as "right to be heard"? The content you requested has been removed. (i.e. I've always been a little sketchy on the differences between static, Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. For more information, see Polymorphism. You are getting warnings due to casting a void* to a type of a different size. The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. u32 -> u8) will truncate Casting from a smaller integer to a larger integer (e.g. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Is there a way to disable it? I was able to disable this with -fms-extensions after getting this from someone on the Cpplang Slack: Looking at "DiagnosticSemaKinds.td" it shows up as err_bad_reinterpret_cast_small_int, https://github.com/llvm-mirror/clang/blob/release_50/include/clang/Basic/DiagnosticSemaKinds.td#L6193 [PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type warning The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. What is this brick with a round back and a stud on the side used for. what happens when we typecast normal variable to void* or any pointer variable? ", "!"? While working with Threads in C, I'm facing the warning, "warning: cast to pointer from integer of different size". This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. This is not a conversion at all. Why did US v. Assange skip the court of appeal? But to just truncate the integer value and not having to fix all the wrong uses of uint32_t just yet, you could use static_cast(reinterpret_cast(ptr)). MIP Model with relaxed integer constraints takes longer to solve than normal model, why? it means that myData is a variable of type "pointer to uint8_t", but it doesn't point to anything yet. That could create all kinds of trouble. value of malloc is bad, like: What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. You use the address-of operator & to do that. To avoid truncating your pointer, cast it to a type of identical size. But then you need to cast your arguments inside your thread function which is quite unsafe cf. How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. char **array; A good thing in general, but if you want to disable the warning, just do it. Why does setupterm terminate the program? Asking for help, clarification, or responding to other answers. Unfortunately, that hardware is 64-bit and the code contains many instances of pointer arithmetic that expects pointers to be 32-bit, i.e. Wrong. How to correctly cast a pointer to int in a 64-bit application? Thanks for contributing an answer to Stack Overflow! I need to convert the argument to an int for later use: The compiler (GCC version 4.2.4) returns the error: You can cast it to an intptr_t type. I want to learn the difference between the three type cast operators: Hi, And, most of these will not even work on gcc4. 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. Based on the design of this function, which modification is right. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. 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. Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. cast to void *' from smaller integer type 'int Join Bytes to post your question to a community of 472,246 software developers and data experts. The proper way is to cast it to another pointer type. However, this specific error is not due to a warning and I can't find any option to disable errors (makes sense, since most errors are fatal). Or you might need to assign a class variable to a variable of an interface type. Implicit conversions - cppreference.com Can I use my Coinbase address to receive bitcoin? 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). User without create permission can create a custom object from Managed package using Custom Rest API. */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j;
Can I use my Coinbase address to receive bitcoin? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Cerror: cast to 'void *' from smaller integer type 'int Not the answer you're looking for? Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. Casting is required when information might be lost in the conversion, or when the conversion might not succeed for other reasons. A boy can regenerate, so demons eat him for years. Short story about swapping bodies as a job; the person who hires the main character misuses his body. Just because you're altering. Don't do that. From the question I presume the OP does. Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. For more information, see How to convert a byte array to an int, How to convert a string to a number, and How to convert between hexadecimal strings and numeric types. 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. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. Were sorry. Or, they are all wrong. Then he wants to convert px to Hello, /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. Casting between types - The Rust Programming Language this question. "I think what you should do is actually pass the address of the variable to the function" Not necessarily. The error I'm getting is: error: cast from pointer to smaller type 'uint32_t' (aka 'unsigned int') loses information. Is "I didn't think it was serious" usually a good defence against "duty to rescue"? error: cast from 'void*' to 'int' loses precision - Stack Overflow Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? The compiler issues the "cast from integer to pointer of different size" warning whenever the value of an integer is converted to a pointer, especially when the memory allocated to a pointer is smaller than the memory allocated to an integer data type. How to correctly type cast (void*)? - social.msdn.microsoft.com What is this brick with a round back and a stud on the side used for? How can I control PNP and NPN transistors together from one pin? Please start a new discussion. If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? In the realm of Android development, two languages have consistently stood out: Java and Kotlin. C99 defines the types "intptr_t" and "uintptr_t" which do . Where can I find a clear diagram of the SPECK algorithm? Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? From that point on, you are dealing with 32 bits. INT31-C. Ensure that integer conversions do not result in lost or Who has a solution to casting from int to void* and back to int, http://www.ungerhu.com/jxh/clc.welcome.txt, http://benpfaff.org/writings/clc/off-topic.html. what does it mean to convert int to void* or vice versa? equal to the original pointer: First you are using a define, which is not a variable. Not the answer you're looking for? dynamic, and reinterpret casting. What differentiates living as mere roommates from living in a marriage-like relationship? For example, you might have an integer variable that you need to pass to a method whose parameter is typed as double. Terrible solution. You might want to typedef, You should change your code to handle this. Making statements based on opinion; back them up with references or personal experience. 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. c printf() C , {} . Referring to N1570 7.20.1.4/p1 (Integer types capable of holding object pointers): The following type designates a signed integer type with the property If this is the data to a thread procedure, then you quite commonly want to pass by value. Going through them one by one would be very tedious and since this is an experimental project anyway, I'm happy to settle for a "hackish" workaround. Because C# is statically-typed at compile time, after a variable is declared, it cannot be declared again or assigned a value of another type unless that type is implicitly convertible to the variable's type. this way I convert an int to a void* which is much better than converting a void* to an int. error: request for member '..' in '..' which is of non-class type. Keep in mind that thrArg should exist till the myFcn() uses it. You use the address-of operator & to do that int x = 10; void *pointer = &x; And in the function you get the value of the pointer by using the dereference operator *: int y = * ( (int *) pointer); Share Improve this answer Follow edited Apr 15, 2013 at 13:58 answered Apr 15, 2013 at 13:53 Some programmer dude 396k 35 399 609 1 For reference types, an implicit conversion always exists from a class to any one of its direct or indirect base classes or interfaces. I don't understand why the following two cases produce different Hi, I've this question: suppose we have two differently typed pointers: I am an entry level C programmer. The most general answer is in no way. 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. In some reference type conversions, the compiler cannot determine whether a cast will be valid. pointer/reference to a derived class pointer/reference. If you are going to pass the address you typically need to exert some more control over the lifetime of the object. 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. Find centralized, trusted content and collaborate around the technologies you use most. 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; cast to void *' from smaller integer type 'int cast to void *' from smaller integer type 'int. Connect and share knowledge within a single location that is structured and easy to search. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. [Solved] Properly casting a `void*` to an integer in C++ Therefore, after you declare i as an int, you cannot assign the string "Hello" to it, as the following code shows: However, you might sometimes need to copy a value into a variable or method parameter of another type. Disabling "cast from pointer to smaller type uint32_t" error in Clang Why did US v. Assange skip the court of appeal? Asking for help, clarification, or responding to other answers. The preprocesor absolutely will not perform arithmetic. 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. But to answer your question: No, you can't disable it, though you can work around it. These kinds of operations are called type conversions. This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. There's no proper way to cast this to int in general case. Which was the first Sci-Fi story to predict obnoxious "robo calls"? cwindowccwindowsword[3]={"ab"};_ab charPersondebug, A, A, , "C" ???? Going through them one by one would be very tedious and since this is an experimental project anyway, I'm happy to settle for a "hackish" workaround. Asking for help, clarification, or responding to other answers. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. Folder's list view has different sized fonts in different folders. 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 insert some debugging/logging logic to Reinterpret_cast if necessary. By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Which was the first Sci-Fi story to predict obnoxious "robo calls"? In C#, you can perform the following kinds of conversions: Implicit conversions: No special syntax is required because the conversion always succeeds and no data will be lost. Connect and share knowledge within a single location that is structured and easy to search. The error message mentions the diagnostic responsible for error message, e.g.
You could use this code, and it would do the same thing as casting ptr to (char*). How can I control PNP and NPN transistors together from one pin? I wish your idea worked. ), For those who are interested. -1, Uggh. One could try -fms-extensions (hopefully not -fms-compatibility), but that would bring all the shebang with it. 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). I can easily imagine a situation where rewriting code using, Disabling "cast from pointer to smaller type uint32_t" error in Clang, https://github.com/llvm-mirror/clang/blob/release_50/include/clang/Basic/DiagnosticSemaKinds.td#L6193, https://github.com/llvm-mirror/clang/blob/release_50/lib/Sema/SemaCast.cpp#L2112, How a top-ranked engineering school reimagined CS curriculum (Ep. The problem is not with casting, but with the target type loosing half of the pointer. For example, if the pointers in a system are stored in 16 bits, but integers are stored in 8 bits, a total of 8 bits would be lost in the . Typical examples include numeric conversion to a type that has less precision or a smaller range, and conversion of a base-class instance to a derived class. is returned by the malloc. What is the correct method to cast an int to a void*? @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. More info about Internet Explorer and Microsoft Edge, How to convert between hexadecimal strings and numeric types, How to safely cast using pattern matching and the as and is operators. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. Thanks for pointing that out. Explanation Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility . For a complete list of all implicit numeric conversions, see the Implicit numeric conversions section of the Built-in numeric conversions article. i Most answers just try to extract 32 useless bits out of the argument. Asking for help, clarification, or responding to other answers. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. 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. Thanks in A colleague asked me something along the lines of the following today. pthread create managing values generated in function (in c), Establishing TCP socket connection between PHP client and C server on Ubuntu. It keeps throwing this exact error message even though both types are 32 bits wide. Can anybody explain how to pass an integer to a function which receives (void * ) as a parameter? If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. how about using uintptr_t, most of your pointer arithmetic may still works. 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. Which reverse polarity protection is better and why? 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. How to set, clear, and toggle a single bit? Explicit conversions (casts): Explicit conversions require a cast expression. c - Cast int to void* - Stack Overflow Definition: C++ introduced a different cast system from C that distinguishes the types of cast operations. Rep Power: 3. Why does Acts not mention the deaths of Peter and Paul? long guarantees a pointer size on Linux on any machine. Find centralized, trusted content and collaborate around the technologies you use most. I'm trying to create a void* from an int. to the original pointer: The following type designates an unsigned integer type with the How to cast/convert pointer to reference in C++, clang error: unknown argument: '-mno-fused-madd' (python package installation failure). rev2023.5.1.43405. Extracting arguments from a list of function calls. For reference types, an explicit cast is required if you need to convert from a base type to a derived type: A cast operation between reference types does not change the run-time type of the underlying object; it only changes the type of the value that is being used as a reference to that object. 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. Needless to say, this will still be wrong. it often does reinterpret_cast(ptr). Many errors come from warnings. rev2023.5.1.43405. Offline ImPer Westermark over 12 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. some reading around on it and why it is sometimes used. 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 ability is most related to insanity: Wisdom, Charisma, Constitution, or Intelligence? Run this code to find how Java handles division and what casting can do to the results. You can use any other pointer, or you can use (size_t), which is 64 bits. Since the culprit is probably something like -Wall which enables many warnings you should keep on, you should selectively disable this single warning. 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). @DavidHeffernan I rephrased that sentence a little. replace uint32_t by uintptr_t wholesale, then fix remaining cases one by one. I am using the UDF of the Ansys Manual Book as a base for what I intended, but I am trying to incorporate a second component to my condensable mixture, being methanol . for (i=0, j=0; j
