But then you need to cast your arguments inside your thread function which is quite unsafe cf. drivers/gpu/drm/mediatek/mtk_disp_ovl_adaptor.c:415:10: warning: cast Not the answer you're looking for? a generic module (say some ADT implementation) that requires a by: William S Fulton |
Could a subterranean river or aquifer generate enough continuous momentum to power a waterwheel for the purpose of producing electricity? 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. This is not a conversion at all. 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. reinterpret_cast<void *>(42)). */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j;
How to Cast a void* ponter to a char without a warning? 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. I am running into the same problem where I am using Clang's static analyzer and clang-tidy to scan code on a 64-bit system that is targeted for a 32-bit system. Explicit conversions (casts): Explicit conversions require a cast expression. It is safer to not make assumptions, but rather check the type. I'm working on a school project that involves porting a large piece of C++ code on an experimental piece of hardware. Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? To learn more, see our tips on writing great answers. 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). Don't do that. In the realm of Android development, two languages have consistently stood out: Java and Kotlin. This allows you to reinterpret the void * as an int. 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, Short story about swapping bodies as a job; the person who hires the main character misuses his body. Why are players required to record the moves in World Championship Classical games? #, In a 64 bit machine with sizeof(int) == 4. This code is a bit odd (but a void* can certainly host a int on all architectures on which GDAL can be compiled), and certainly unused by anyone, so you could just remove the GetInternalHandle () implementation as well if you prefer. 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. You can use any other pointer, or you can use (size_t), which is 64 bits. Examples include conversions from smaller to larger integral types, and conversions from derived classes to base classes. I agree that you should bite the bullet and fix the code to use the correct integer type. Two MacBook Pro with same model number (A1286) but different year. rev2023.5.1.43405. This is what the second warning is telling you. 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. For a fairly recent compiler (that supports C99) you should not store or represent address as plain int value. Generating points along line with specifying the origin of point generation in QGIS. */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. 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. Casting type void to uint8_t - Arduino Forum "Signpost" puzzle from Tatham's collection. what does it mean to convert int to void* or vice versa? Unfortunately, that hardware is 64-bit and the code contains many instances of pointer arithmetic that expects pointers to be 32-bit, i.e. 1.6. Casting and Ranges of Variables AP CSAwesome Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? You might want to typedef, You should change your code to handle this. For some type X he has: Remembering to delete the pointer after use so that we don't leak. Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? But gcc always give me a warning, that i cannot cast an int to a void*. 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 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). And in this context, it is very very very common to see programmers lazily type cast the. Making statements based on opinion; back them up with references or personal experience. I don't understand why the following two cases produce different Hi, I've this question: suppose we have two differently typed pointers: Implementation-dependent. I had this error while trying to cross compile the header from libstdc++ 5.4.0 with clang 7.0.1 for ARM. One could try -fms-extensions (hopefully not -fms-compatibility), but that would bring all the shebang with it. @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. It's always a good practice to put your #define's in brackets to avoid such surprise. Short story about swapping bodies as a job; the person who hires the main character misuses his body. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. error: request for member '..' in '..' which is of non-class type. To avoid truncating your pointer, cast it to a type of identical size. How to find the size of an array (from a pointer pointing to the first element array)? Just because you're altering. And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. The casting operators (int) and (double) are used right next to a number or variable to create a temporary value converted to a different data type. Which reverse polarity protection is better and why? From the question I presume the OP does. I don't see how anything bad can happen . Asking for help, clarification, or responding to other answers. pthread passes the argument as a void*. A nit: in your version, the cast to void * is unnecessary. dynamic_cast safely converts pointers and references to classes up, down and sideways along the inheritance hierarchy - according to CppReference. error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. Is a downhill scooter lighter than a downhill MTB with same performance? void *ptr; int n = (int)ptr; So in c++ i tried below int n = atoi (static_cast<const char*> (ptr)); This crashes when i run. 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. 4. Type Conversions - C in a Nutshell [Book] - O'Reilly Online Learning Mar 30, 2020 at 11:12am or, Array with multiple data types? Keep in mind that thrArg should exist till the myFcn() uses it. what happens when we typecast normal variable to void* or any pointer variable? How to correctly cast a pointer to int in a 64-bit application? To avoid truncating your pointer, cast it to a type of identical size. For more information, see the Conversions section of the C# language specification. (i.e. What is "cast from integer to pointer of different size" warning? This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). 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. 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. Canadian of Polish descent travel to Poland with Canadian passport. arduino ide - Incompatible types in assignment of 'uint8_t {aka then converted back to pointer to void, and the result will compare 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)). Making statements based on opinion; back them up with references or personal experience. Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, I would try to fix the code instead. /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. 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. 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. The -fms-extensions flag resolved the issue. The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. For the second example you can make sure that sizeof (int) <= sizeof (void *) by using a static_assert -- this way at least you'll get a notice about it. rev2023.5.1.43405. Why is it shorter than a normal address? So you know you can cast it back like this. c - How to cast an integer to void pointer? - Stack Overflow If we had a video livestream of a clock being sent to Mars, what would we see? Posted on Author Author Passing negative parameters to a wolframscript, Generating points along line with specifying the origin of point generation in QGIS. 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. "jacob navia" wrote: This question has probably been asked a million time, but here it comes Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. X* px = new X; INT36-C. Converting a pointer to integer or integer to pointer Thanks for contributing an answer to Stack Overflow! If the types are from the same inheritance tree, then you should either use dynamic_casts or even better, you should benefit from dynamic dispatching.. dynamic_cast is slightly better, but still should be avoided. for (i=0, j=0; j works only in b/w ! I am compiling this program in linux gcc compiler.. Just want to point out that the purpose of threads is, +1 absolutely true, but if you take you time to write struct {}, you can save a lot of troubles in the future when you want to receive/send more data then just an int. Was Aristarchus the first to propose heliocentrism? I'm not sure how to tell Clang (it's tools, really) that the platform is a 32-bit platform and to stop complaining. 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. a cast of which the programmer should be aware of what (s)he is doing. Thanks for contributing an answer to Stack Overflow! However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted.
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