Casting type void to uint8_t - Arduino Forum replace uint32_t by uintptr_t wholesale, then fix remaining cases one by one. 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. LettuceConnectionFactory was destroyed and cannot be used - CSDN There is no "correct" way to store a 64-bit pointer in an 32-bit integer. On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. cwindowccwindowsword[3]={"ab"};_ab charPersondebug, A, A, , "C" ???? #, Nov 14 '05 Type conversions - cplusplus.com following block Hello, Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. a generic module (say some ADT implementation) that requires a by: William S Fulton | 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 You use the address-of operator & to do that. 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. for (i=0, j=0; jClang warnings for an invalid casting? - The FreeBSD Forums To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. Mar 30, 2020 at 11:12am I assumed that gcc makes a 65536 out of my define, but I was wrong. This forum has migrated to Microsoft Q&A. "jacob navia" wrote: This question has probably been asked a million time, but here it comes How to get the error message from the error code returned by GetLastError()? Did the drapes in old theatres actually say "ASBESTOS" on them? Is it safe to publish research papers in cooperation with Russian academics? C# provides the is operator to enable you to test for compatibility before actually performing a cast. I would like to know the reason. So instead I modified the implementation of malloc to ensure it never allocates memory above the 4GB limit. rev2023.3.3.43278. 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. Since all pointers on 64-bit Windows are 64 bits, you are growing the data size from 32 bits backto 64 bits. 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. @Martin York: No, it doesn't depend on endiannness. "I think what you should do is actually pass the address of the variable to the function" Not necessarily. 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. 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. 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. @Shahbaz you could but I will not suggest to a C newbie to use globals. If the sizes are different then endianess comes into play. rev2023.5.1.43405. 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. void* -> integer -> void* rather than integer -> void* -> integer. 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. 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 Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. Does a password policy with a restriction of repeated characters increase security? If you need to keep the returned address, just keep it as void*. For integral types, this means the range of the source type is a proper subset of the range for the target type. 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. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Examples include conversions from smaller to larger integral types, and conversions from derived classes to base classes. Both languages have been widely adopted by How to plot text in color? Two MacBook Pro with same model number (A1286) but different year. u8 -> u32) will zero-extend if the source is unsigned sign-extend if the source is signed Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? The next Access Europe Meeting is on Wed 3 May 2023. 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. The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. Connect and share knowledge within a single location that is structured and easy to search. In some reference type conversions, the compiler cannot determine whether a cast will be valid. The -fms-extensions flag resolved the issue. My code is all over the place now but I appreciate you all helping me on my journey to mastery! Thanks in A colleague asked me something along the lines of the following today. Please start a new discussion. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. The preprocessor will replace your code by this: This is unlikely what you are trying to do. 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). 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 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! 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. it means that myData is a variable of type "pointer to uint8_t", but it doesn't point to anything yet. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. Not the answer you're looking for? I think the solution 3> should be the correct one. 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). Implicit conversions - cppreference.com And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. A nit: in your version, the cast to void * is unnecessary. What you do here is undefined behavior, and undefined behavior of very practical sort. This thread has been closed and replies have been disabled. @DavidHeffernan I rephrased that sentence a little. It is safer to not make assumptions, but rather check the type. I had this error while trying to cross compile the header from libstdc++ 5.4.0 with clang 7.0.1 for ARM. I saw on a couple of recent posts people saying that casting the return Why is it shorter than a normal address? What differentiates living as mere roommates from living in a marriage-like relationship? I don't understand why the following two cases produce different Hi, I've this question: suppose we have two differently typed pointers: Embedded hyperlinks in a thesis or research paper. "Signpost" puzzle from Tatham's collection. You could use this code, and it would do the same thing as casting ptr to (char*). Making statements based on opinion; back them up with references or personal experience. Instead of using a long cast, you should cast to size_t. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. From the question I presume the OP does. Episode about a group who book passage on a space ship controlled by an AI, who turns out to be a human who can't leave his ship? Find centralized, trusted content and collaborate around the technologies you use most. What is this brick with a round back and a stud on the side used for. Thanks for contributing an answer to Stack Overflow! What is this brick with a round back and a stud on the side used for? 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. what happens when we typecast normal variable to void* or any pointer variable? #, In a 64 bit machine with sizeof(int) == 4. Is pthread_join a must when using pthread in linux? It's not them. I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. Again, all of the answers above missed the point badly. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. converted back to pointer to void, and the result will compare equal The program will not compile without the cast. Use returnPtr[j] = (void *) ((long)ptr + i); ). long guarantees a pointer size on Linux on any machine. Storage management is an important module of database, which can be subdivided into memory management and external memory management. Thank you all for your feedback. 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. You can use any other pointer, or you can use (size_t), which is 64 bits. cast to void *' from smaller integer type 'int-tdecu credit scoretdecu credit score Is "I didn't think it was serious" usually a good defence against "duty to rescue"? Without RTTI your code will be cleaner | Sandor Dargo's Blog The most general answer is in no way. This option of Python is missing in matplotlibcpp within Visual Studio -> works only in b/w ! dynamic, and reinterpret casting. Find centralized, trusted content and collaborate around the technologies you use most. */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. this question. The following program casts a double to an int. So make sure you understand what you are doing! Therefore, you need to change it to long long instead of long in windows for 64 bits. You are right! The error message mentions the diagnostic responsible for error message, e.g. To learn more, see our tips on writing great answers. c - Cast int to void* - Stack Overflow pointer/reference to a derived class pointer/reference. The only. How to convert a factor to integer\numeric without loss of information? The Test method has an Animal parameter, thus explicitly casting the argument a to a Reptile makes a dangerous assumption. If any, how can the original function works without errors if we just ignore the warning. It's an int type guaranteed to be big enough to contain a pointer. How a top-ranked engineering school reimagined CS curriculum (Ep. Can my creature spell be countered if I cast a split second spell after it? What does it mean to convert int to void* or vice versa? Cerror: cast to 'void *' from smaller integer type 'int [Solved] Properly casting a `void*` to an integer in C++ That's not a good idea if the original object (that was cast to void*) was an integer. Casting int to void* : r/C_Programming - Reddit C++ how to get the address stored in a void pointer? This is not a conversion at all. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? The problem is not with casting, but with the target type loosing half of the pointer. 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. Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? 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 . Conversions with helper classes: To convert between non-compatible types, such as integers and System.DateTime objects, or hexadecimal strings and byte arrays, you can use the System.BitConverter class, the System.Convert class, and the Parse methods of the built-in numeric types, such as Int32.Parse. # * # (intptr_t) # # warning: cast to pointer from integer of different size # (intptr_t)IDE # (void*) . Needless to say, this will still be wrong. Put your define inside a bracket: without a problem. Canadian of Polish descent travel to Poland with Canadian passport. Why does flowing off the end of a non-void function without returning a value not produce a compiler error? 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. rev2023.5.1.43405. How should a standardized and beautiful flowchart be designed? c - type casting integer to void* - Stack Overflow For example, the string cannot be implicitly converted to int. No idea how it amassed 27 upvotes?! Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. MIP Model with relaxed integer constraints takes longer to solve than normal model, why? 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. For example, a variable of type long (64-bit integer) can store any value that an int (32-bit integer) can store. to the original pointer: The following type designates an unsigned integer type with the Asking for help, clarification, or responding to other answers. Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? Generating points along line with specifying the origin of point generation in QGIS. (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 Infact I know several systems where that does not hold. Half your pointer will be garbage. 472,096 Members | 2,054 Online. Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. this way you won't get any warning. i dynamic_cast safely converts pointers and references to classes up, down and sideways along the inheritance hierarchy - according to CppReference. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. It's always a good practice to put your #define's in brackets to avoid such surprise. So you know you can cast it back like this. Casting a pointer to void* and back is valid use of reinterpret_cast<>. comment:4 by Kurt Schwehr, 8 years ago r28216 removes OGDIDataset:: GetInternalHandle from trunk Please tell me error: cast from 'void*' to 'int' loses precision, How a top-ranked engineering school reimagined CS curriculum (Ep. Why don't we use the 7805 for car phone chargers? How to cast/convert pointer to reference in C++, clang error: unknown argument: '-mno-fused-madd' (python package installation failure). Were sorry. I think using intptr_t is the correct intermediate here, since it's guaranteed to be large enough to contain the integral value of the void*, and once I have an integer value I can then truncate it without causing the compiler to complain. Where can I find a clear diagram of the SPECK algorithm? Keep in mind that thrArg should exist till the myFcn() uses it. For more information, see User-defined conversion operators. For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. Boolean algebra of the lattice of subspaces of a vector space? How do I force make/GCC to show me the commands? Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" error: cast from 'void*' to 'int' loses precision - Stack Overflow By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. If we had a video livestream of a clock being sent to Mars, what would we see? So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. Yes, for the reason you mentioned that's the proper intermediate type. Cvoid*int - Alan_LJP - It is possible for a cast operation that compiles correctly to fail at run time. Short story about swapping bodies as a job; the person who hires the main character misuses his body. What would you do next year when you need to port it to yet another experimental hardware? 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 a top-ranked engineering school reimagined CS curriculum (Ep. But gcc always give me a warning, that i cannot cast an int to a void*. 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). cast to void *' from smaller integer type 'int Use #include to define it. This is a fine way to pass integers to new pthreads, if that is what you need. again. 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. Embedded hyperlinks in a thesis or research paper. But to answer your question: No, you can't disable it, though you can work around it. 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 example, you might have an integer variable that you need to pass to a method whose parameter is typed as double. 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. How to correctly type cast (void*)? - social.msdn.microsoft.com @Xax: Here's a fixed version, without the race condition: gist.github.com/depp/241d6f839b799042c409, gist.github.com/depp/3f04508a88a114734195, How a top-ranked engineering school reimagined CS curriculum (Ep. 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? When is casting void pointer needed in C? Asking for help, clarification, or responding to other answers. I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. Just because you're altering. Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? I'm working on a school project that involves porting a large piece of C++ code on an experimental piece of hardware. If you call your thread creation function like this, then the void* arriving inside of myFcn has the value of the int you put into it. How to correctly cast a pointer to int in a 64-bit application? In C (int)b is called an explicit conversion, i.e. However, if a conversion cannot be made without a risk of losing information, the compiler requires that you perform an explicit conversion, which is called a cast. The OP wanted to convert a pointer value to a int value, instead, most the answers, one way or the other, tried to wrongly convert the content of arg points to to a int value. I have read in one of old posting that don't cast of pointer which Visit Microsoft Q&A to post new questions. c - How to cast an integer to void pointer? - Stack Overflow I would create a structure and pass that as void* to pthread_create. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. how to convert void* to int - C++ Forum - cplusplus.com error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. 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. User-defined conversions: User-defined conversions are performed by special methods that you can define to enable explicit and implicit conversions between custom types that do not have a base classderived class relationship.
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