cast to 'void *' from smaller integer type 'int'

last post by: I'm looking for the name of the following casting style in order to do Should I re-do this cinched PEX connection? 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. You are just making it bigger by tricking the compiler and the ABI. There is no "correct" way to store a 64-bit pointer in an 32-bit integer. it often does reinterpret_cast(ptr). 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. How should a standardized and beautiful flowchart be designed? Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? @Martin York: No, it doesn't depend on endiannness. If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. Connect and share knowledge within a single location that is structured and easy to search. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? 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. it often does reinterpret_cast<uint32_t> (ptr). This is not even remotely "the correct answer". this question. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The next Access Europe Meeting is on Wed 3 May 2023. Find centralized, trusted content and collaborate around the technologies you use most. Why did US v. Assange skip the court of appeal? However, you are also casting the result of this operation to (void*). They should do their job unless your code is too tricky. Now, what happens when I run it with the thread sanitizer? Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. @DavidHeffernan I rephrased that sentence a little. Is a downhill scooter lighter than a downhill MTB with same performance? It does not because. Why is it shorter than a normal address? If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? MIP Model with relaxed integer constraints takes longer to solve than normal model, why? Since gcc compiles that you are performing arithmetic between void* and an int (1024). Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). a generic module (say some ADT implementation) that requires a by: William S Fulton | Write values of different data types in sequence in memory? He also rips off an arm to use as a sword. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? That could create all kinds of trouble. How can I control PNP and NPN transistors together from one pin? returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size); By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. equal to the original pointer: First you are using a define, which is not a variable. How can I control PNP and NPN transistors together from one pin? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Generating points along line with specifying the origin of point generation in QGIS. If the data types are compatible, then Java will perform the conversion automatically known as Automatic Type Conversion, and if not then they need to be cast or converted explicitly. You use the address-of operator & to do that. I agree passing a dynamically allocated pointer is fine (and I think the best way). Using an integer address (like &x) is probably wrong, indeed each modification you will execute on x will affect the pass behaviour. So make sure you understand what you are doing! The preprocesor absolutely will not perform arithmetic. i32 -> u32) is a no-op Casting from a larger integer to a smaller integer (e.g. I cannot reverse my upvote of user384706's answer, but it's wrong. To learn more, see our tips on writing great answers. Save this piece of code as mycast.hpp and add -include mycast.hpp to your Makefile. For example, a variable of type long (64-bit integer) can store any value that an int (32-bit integer) can store. (Also, check out how it prints "5" twice), passing a unique pointer to each thread wont race, and you can get/save any kind of information in the th struct. 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. The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. 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. The only. Just because you're altering. Find centralized, trusted content and collaborate around the technologies you use most. 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. Thanks in A colleague asked me something along the lines of the following today. Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? Use #include to define it. 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]. 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. 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Say I want to make You may declare a const int variable and cast its reference to the void*. 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 C / C++ Forums on Bytes. Did the drapes in old theatres actually say "ASBESTOS" on them? this way you won't get any warning. rev2023.5.1.43405. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. property that any valid pointer to void can be converted to this type, or, Array with multiple data types? Why don't we use the 7805 for car phone chargers? I agree that you should bite the bullet and fix the code to use the correct integer type. If a negative integer value is converted to an unsigned type, the resulting value corresponds to its 2's complement bitwise representation (i.e., If the conversion is from a floating-point type to an integer type, the value is truncated (the decimal part is removed). What does 'They're at four. Based on the design of this function, which modification is right. following block Hello, 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! However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. What is this brick with a round back and a stud on the side used for? You can use any other pointer, or you can use (size_t), which is 64 bits. 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. (i.e. This is what the second warning is telling you. Making statements based on opinion; back them up with references or personal experience. Why are players required to record the moves in World Championship Classical games? Connect and share knowledge within a single location that is structured and easy to search. 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 do I check if a string represents a number (float or int)? 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. Yes, for the reason you mentioned that's the proper intermediate type. Interpreting non-statistically significant results: Do we have "no evidence" or "insufficient evidence" to reject the null? If the sizes are different then endianess comes into play. cwindowccwindowsword[3]={"ab"};_ab charPersondebug, A, A, , "C" ???? There is absolutely not gurantee that sizeof(int) <= sizeof(void*). 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. 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. Keep in mind that thrArg should exist till the myFcn() uses it. What differentiates living as mere roommates from living in a marriage-like relationship? If the function had the correct signature you would not need to cast it explicitly. Find centralized, trusted content and collaborate around the technologies you use most. ', referring to the nuclear power plant in Ignalina, mean? The preprocessor will replace your code by this: This is unlikely what you are trying to do. No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. Which was the first Sci-Fi story to predict obnoxious "robo calls"? Visit Microsoft Q&A to post new questions. Unfortunately, that hardware is 64-bit and the code contains many instances of pointer arithmetic that expects pointers to be 32-bit, i.e. I had this error while trying to cross compile the header from libstdc++ 5.4.0 with clang 7.0.1 for ARM. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. 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 I wish your idea worked. If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. "Signpost" puzzle from Tatham's collection. ERROR: incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int', error: cast to 'string' (aka 'char *') from smaller integer type 'int' [-Werror,-Wint-to-pointer-cast], error: incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int' C, warning: initialization of 'unsigned char' from 'uint8_t *' {aka 'unsigned char *'} makes integer from pointer without a cast [-Wint-conversion], Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Can I use the spell Immovable Object to create a castle which floats above the clouds? Why does Acts not mention the deaths of Peter and Paul? Not the answer you're looking for? 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. Find centralized, trusted content and collaborate around the technologies you use most. Connect and share knowledge within a single location that is structured and easy to search. With that declaration, you can later say: myData = "custom string"; That points the myData pointer to the address of your constant string. 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 . What is this brick with a round back and a stud on the side used for. Embedded hyperlinks in a thesis or research paper. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. For example, you might have an integer variable that you need to pass to a method whose parameter is typed as double. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. You can insert some debugging/logging logic to Reinterpret_cast if necessary. Question is, how do I explain this to Clang? Thanks for contributing an answer to Stack Overflow! Folder's list view has different sized fonts in different folders. But then you need to cast your arguments inside your thread function which is quite unsafe cf. My code is all over the place now but I appreciate you all helping me on my journey to mastery! Both languages have been widely adopted by How to plot text in color? 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. @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. For example, the string cannot be implicitly converted to int. Why does Acts not mention the deaths of Peter and Paul? My blogs h2 and other tags are in these manner. Converting a void* to an int is non-portable way that may work or may not! Just edited. But gcc always give me a warning, that i cannot cast an int to a void*. Asking for help, clarification, or responding to other answers. Usually that means the pointer is allocated with. 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. One could try -fms-extensions (hopefully not -fms-compatibility), but that would bring all the shebang with it. Put your define inside a bracket: without a problem. Canadian of Polish descent travel to Poland with Canadian passport. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. 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). 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" (. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. Rep Power: 3. MIP Model with relaxed integer constraints takes longer to solve than normal model, why? This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). Thanks for contributing an answer to Stack Overflow! */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; Thanks for pointing that out. pointer/reference to a derived class pointer/reference. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. [-Wextra-tokens] (if it doesn't, remove the -fno-diagnostics-show-option flag). And in the function you get the value of the pointer by using the dereference operator *: Please read why glib provide macros for this kind of conversions, there's no need to repeat the text here. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. Explanation Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility . Is it safe to publish research papers in cooperation with Russian academics? Syntax static_cast< new-type > ( expression ) Returns a value of type new-type . By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use. Why is it shorter than a normal address? User without create permission can create a custom object from Managed package using Custom Rest API. 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. Needless to say, this will still be wrong. 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. @jackdoe: It's a waste of human life to write code that "you may need in the future". The following program casts a double to an int. I am an entry level C programmer. Since the culprit is probably something like -Wall which enables many warnings you should keep on, you should selectively disable this single warning. For reference types, an implicit conversion always exists from a class to any one of its direct or indirect base classes or interfaces. 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. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. 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). linux c-pthreads: problem with local variables. This option of Python is missing in matplotlibcpp within Visual Studio -> works only in b/w ! I would like to know the reason. The content you requested has been removed. If we had a video livestream of a clock being sent to Mars, what would we see? void* -> integer -> void* rather than integer -> void* -> integer. What you do here is undefined behavior, and undefined behavior of very practical sort. 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;. How to convert a factor to integer\numeric without loss of information? Since all pointers on 64-bit Windows are 64 bits, you are growing the data size from 32 bits backto 64 bits. So,solution #3 works just fine. The main point is: a pointer has a platform dependent size. You think by casting it here that you are avoiding the problem! In this case, casting the pointer back to an integer is meaningless, because . By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Is pthread_join a must when using pthread in linux? 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 How to correctly cast a pointer to int in a 64-bit application? Find centralized, trusted content and collaborate around the technologies you use most. @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. You need to pass an actual pointer. @DietrichEpp can you explain what is race condition with using. Casting a pointer to void* and back is valid use of reinterpret_cast<>. there How should an excellent flowchart be drawn? cast to void *' from smaller integer type 'int-tdecu credit scoretdecu credit score Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Not the answer you're looking for? If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. So you know you can cast it back like this. It keeps throwing this exact error message even though both types are 32 bits wide. 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. Is there any known 80-bit collision attack? 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. 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 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. 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. 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? It's always a good practice to put your #define's in brackets to avoid such surprise. What is this brick with a round back and a stud on the side used for? rev2023.5.1.43405. On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Can anybody explain how to pass an integer to a function which receives (void * ) as a parameter? The error I'm getting is: error: cast from pointer to smaller type 'uint32_t' (aka 'unsigned int') loses information. No idea how it amassed 27 upvotes?! Can I use an 11 watt LED bulb in a lamp rated for 8.6 watts maximum? 1) zero or one conversion from the following set: lvalue-to-rvalue conversion, array-to-pointer conversion, and function-to-pointer conversion; 2) zero or one numeric promotion or numeric conversion; 3) zero or one function pointer conversion; (since C++17) 4) zero or one qualification conversion. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. 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 . It seems both static_cast and dynamic_cast can cast a base class On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? 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). How to force Unity Editor/TestRunner to run at full speed when in background? Posted on Author Author does lazarbeam have a wife; Books. 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. Making statements based on opinion; back them up with references or personal experience. (void *)(long)i, Copyright 2011-2023 SegmentFault. Say you hack this successfully. 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. 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. u32 -> u8) will truncate Casting from a smaller integer to a larger integer (e.g. 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. Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul 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. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. From: Hans de Goede <hdegoede@redhat.com> To: Mark Gross <mgross@linux.intel.com> Cc: Hans de Goede <hdegoede@redhat.com>, Andy Shevchenko <andy@infradead.org>, platform-driver-x86@vger.kernel.org, kernel test robot <lkp@intel.com> Subject: [PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type warning Date: Mon, 23 Jan 2023 14:28:24 +0100 [thread overview] Message-ID: <20230123132824. . Not the answer you're looking for? For more information, see Polymorphism. 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. C# provides the is operator to enable you to test for compatibility before actually performing a cast. Is a downhill scooter lighter than a downhill MTB with same performance? I saw on a couple of recent posts people saying that casting the return To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. ), For those who are interested. If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. Asking for help, clarification, or responding to other answers. To learn more, see our tips on writing great answers. For more information, see User-defined conversion operators. A nit: in your version, the cast to void * is unnecessary. For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. The Test method has an Animal parameter, thus explicitly casting the argument a to a Reptile makes a dangerous assumption. How can I control PNP and NPN transistors together from one pin? Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. A good thing in general, but if you want to disable the warning, just do it. If int is no larger than pointer to void then one way to store the value is by simply copying the bytes: int i . Can you still use Commanders Strike if the only attack available to forego is an attack against an ally?