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

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. How can I control PNP and NPN transistors together from one pin? The most general answer is - in no way. I am an entry level C programmer. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. MIP Model with relaxed integer constraints takes longer to solve than normal model, why? It does not because. I'll edit accordingly. To learn more, see our tips on writing great answers. Interpreting non-statistically significant results: Do we have "no evidence" or "insufficient evidence" to reject the null? The semantics of numeric casts are: Casting between two integers of the same size (e.g. Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. Unfortunately, that hardware is 64-bit and the code contains many instances of pointer arithmetic that expects pointers to be 32-bit, i.e. Thank you all for your feedback. Why did US v. Assange skip the court of appeal? To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page. The following program casts a double to an int. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. 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). 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. How can I control PNP and NPN transistors together from one pin? Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. So instead I modified the implementation of malloc to ensure it never allocates memory above the 4GB limit. "Signpost" puzzle from Tatham's collection. Passing negative parameters to a wolframscript, Generating points along line with specifying the origin of point generation in QGIS. 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 allows you to reinterpret the void * as an int. The only. char **array; He also rips off an arm to use as a sword. How create a simple program using threads in C? A boy can regenerate, so demons eat him for years. 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. Storage management is an important module of database, which can be subdivided into memory management and external memory management. Generating points along line with specifying the origin of point generation in QGIS. Ubuntu won't accept my choice of password, Adding EV Charger (100A) in secondary panel (100A) fed off main (200A), Passing negative parameters to a wolframscript. What are the advantages of running a power tool on 240 V vs 120 V? what does it mean to convert int to void* or vice versa? If the sizes are different then endianess comes into play. Is pthread_join a must when using pthread in linux? 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. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. Use returnPtr[j] = (void *) ((long)ptr + i); ). No idea how it amassed 27 upvotes?! 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. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. 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. I assumed that gcc makes a 65536 out of my define, but I was wrong. 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 C (int)b is called an explicit conversion, i.e. If we had a video livestream of a clock being sent to Mars, what would we see? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. I have read in one of old posting that don't cast of pointer which rev2023.5.1.43405. 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" (. 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. 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. Run this code to find how Java handles division and what casting can do to the results. Why does setupterm terminate the program? Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? The preprocessor will replace your code by this: This is unlikely what you are trying to do. 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. @DietrichEpp can you explain what is race condition with using. Once you manage to make this cast, then what?! This is flat out wrong. But to answer your question: No, you can't disable it, though you can work around it. But then you need to cast your arguments inside your thread function which is quite unsafe cf. 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. Short story about swapping bodies as a job; the person who hires the main character misuses his body. pthread create managing values generated in function (in c), Establishing TCP socket connection between PHP client and C server on Ubuntu. Not the answer you're looking for? 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). Not the answer you're looking for? What is the correct method to cast an int to a void*? This is not a conversion at all. 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! The error I'm getting is: error: cast from pointer to smaller type 'uint32_t' (aka 'unsigned int') loses information. # * # (intptr_t) # # warning: cast to pointer from integer of different size # (intptr_t)IDE # (void*) . Yes, for the reason you mentioned that's the proper intermediate type. Pros: The problem with C casts is the ambiguity of the operation; sometimes you are doing a conversion (e.g., (int)3.5) and sometimes you are doing a cast (e.g., (int)"hello"); C++ casts avoid this. The correct answer is, if one does not mind losing data precision. 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. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. And, most of these will not even work on gcc4. Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul That's not a good idea if the original object (that was cast to void*) was an integer. I'm having a little bit of trouble regarding pointer casting in my program. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. You are right! Please start a new discussion. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . 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. */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. For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Were sorry. What were the most popular text editors for MS-DOS in the 1980s? Did the drapes in old theatres actually say "ASBESTOS" on them? Find centralized, trusted content and collaborate around the technologies you use most. "jacob navia" wrote: This question has probably been asked a million time, but here it comes By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. For integral types, this means the range of the source type is a proper subset of the range for the target type. c printf() C , {} . 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)). Generating points along line with specifying the origin of point generation in QGIS. Asking for help, clarification, or responding to other answers. 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? 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. For a fairly recent compiler (that supports C99) you should not store or represent address as plain int value. Thanks for contributing an answer to Stack Overflow! Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Asking for help, clarification, or responding to other answers. How do I count the number of sentences in C using ". 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. It's an int type guaranteed to be big enough to contain a pointer. However, you are also casting the result of this operation to (void*). This rule is particularly true for integer values that originate from untrusted sources and are used in any of the following ways: Integer operands of any pointer arithmetic, including array indexing By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Use #include to define it. long guarantees a pointer size on Linux on any machine. Why did DOS-based Windows require HIMEM.SYS to boot? Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. pointer/reference to a derived class pointer/reference. Making statements based on opinion; back them up with references or personal experience. The reinterpret_cast makes the int the size of a pointer and the warning will stop. what happens when we typecast normal variable to void* or any pointer variable? A nit: in your version, the cast to void * is unnecessary. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. this way you won't get any warning. #, In a 64 bit machine with sizeof(int) == 4. linux c-pthreads: problem with local variables. Definition: C++ introduced a different cast system from C that distinguishes the types of cast operations. The following program casts a double to an 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. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. Then he wants to convert px to Hello, Connect and share knowledge within a single location that is structured and easy to search. Can I use the spell Immovable Object to create a castle which floats above the clouds? Half your pointer will be garbage. The C Standard allows any object pointer to be cast to and from void *. replace uint32_t by uintptr_t wholesale, then fix remaining cases one by one. So,solution #3 works just fine. /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. 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 am looking to clean up the 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. To learn more, see our tips on writing great answers. 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. Examples include conversions from smaller to larger integral types, and conversions from derived classes to base classes. The proper way is to cast it to another pointer type. 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. 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. value of malloc is bad, like: Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, Setting a buffer of char* with intermediate casting to int*. With that declaration, you can later say: myData = "custom string"; That points the myData pointer to the address of your constant string. following block Hello, I had this error while trying to cross compile the header from libstdc++ 5.4.0 with clang 7.0.1 for ARM. Extracting arguments from a list of function calls. Making statements based on opinion; back them up with references or personal experience. As shown in the following example, a type cast that fails at run time will cause an InvalidCastException to be thrown. But this code pass the normal variable .. 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). When do you use in the accusative case? 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? 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. Rep Power: 3. Can I use an 11 watt LED bulb in a lamp rated for 8.6 watts maximum? And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, I would try to fix the code instead. To avoid truncating your pointer, cast it to a type of identical size. (void *)(long)i, Copyright 2011-2023 SegmentFault. 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. that any valid pointer to void can be converted to this type, then Why did US v. Assange skip the court of appeal? 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 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 . They should do their job unless your code is too tricky. property that any valid pointer to void can be converted to this type, Posted on Author Author MIP Model with relaxed integer constraints takes longer to solve than normal model, why? how to cascade 2d int array to 2d void pointer array? It's not them. Why is it shorter than a normal address? Can anybody explain how to pass an integer to a function which receives (void * ) as a parameter? It's always a good practice to put your #define's in brackets to avoid such surprise. This is not even remotely "the correct answer". @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. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. @DavidHeffernan I rephrased that sentence a little. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" The problem is not with casting, but with the target type loosing half of the pointer. Not the answer you're looking for? 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 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. How to find the size of an array (from a pointer pointing to the first element array)? Short story about swapping bodies as a job; the person who hires the main character misuses his body. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. 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! dynamic, and reinterpret casting. is there such a thing as "right to be heard"? Nov 14 '05 Is there a way to disable it? This is an old C callback mechanism so you can't change that. Offline ImPer Westermark over 12 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. A boy can regenerate, so demons eat him for years. I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. I don't understand why the following two cases produce different Hi, I've this question: suppose we have two differently typed pointers: Many errors come from warnings. The program will not compile without the cast. One could try -fms-extensions (hopefully not -fms-compatibility), but that would bring all the shebang with it. Which was the first Sci-Fi story to predict obnoxious "robo calls"? While working with Threads in C, I'm facing the warning, "warning: cast to pointer from integer of different size". Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, error: cast from void* to int loses precision, cast to pointer from integer of different size, pthread code. For some type X he has: Converting a void* to an int is non-portable way that may work or may not! error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. Convert integers, floating-point values and enum types to enum types. Folder's list view has different sized fonts in different folders. Most answers just try to extract 32 useless bits out of the argument. Can I use the spell Immovable Object to create a castle which floats above the clouds? These kinds of operations are called type conversions. Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? User without create permission can create a custom object from Managed package using Custom Rest API. Why don't we use the 7805 for car phone chargers? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. (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 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; Embedded hyperlinks in a thesis or research paper. For example, (double) 1/3 will give a double result instead of an int 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.

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