It is easier to understand and write than any other assembly language. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. To learn more, see our tips on writing great answers. */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. Is pthread_join a must when using pthread in linux? 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 SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); What is the difference between const int*, const int * const, and int const *? this way I convert an int to a void* which is much better than converting a void* to an int. that any valid pointer to void can be converted to this type, then If pointers are 64 bits and ints are 32 bits, an int is too small to hold a pointer value. How to convert a factor to integer\numeric without loss of information? However even though their types are different, the address is going to be the same. There's probably little you can do except look or hope for a fixed 2.x version or upgrade to 3.x (I would assume it's 64-bit safe but this is just a guess, do research this issue before you upgrade). This is a fine way to pass integers to new pthreads, if that is what you need. vegan) just to try it, does this inconvenience the caterers and staff? [] ExplanatioUnlike static_cast, but like const_cast, the reinterpret_cast expression does not compile to any CPU instructions (except when converting between integers and pointers or on obscure architectures where pointer representation depends on its type). To subscribe to this RSS feed, copy and paste this URL into your RSS reader. No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. Before I update Xcode, my project still can build and run normally with all devices. 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 Martian regolith be easily melted with microwaves? windows meson: cast to smaller integer type 'unsigned long' from 'void *'. I am compiling this program in linux gcc compiler.. Error while setting app icon and launch image in xcode 5.1. this way you won't get any warning. Whats the grammar of "For those whose stories they are"? There's no proper way to cast this to int in general case. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. ^~~~~~~~~~~~~~~~~~~~ Recovering from a blunder I made while emailing a professor. Safe downcast may be done with dynamic_cast. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' 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; You can convert the values from one type to another explicitly using the cast operator as follows (type_name) expression So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Find centralized, trusted content and collaborate around the technologies you use most. 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. What is the purpose of non-series Shimano components? I have looked around and can't seem to find any information on how to do this. Wrong. SCAN_PUT_ATTR(key, ATTR, skey, FUNC); 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. Why is there a voltage on my HDMI and coaxial cables? Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). Asking for help, clarification, or responding to other answers. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. If the sizes are different then endianess comes into play. Such pointers can be stored in 32-bit data types (for instance, int, DWORD). I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. SCAN_PUT(ATTR, NULL); The correct answer is, if one does not mind losing data precision. If you are going to pass the address you typically need to exert some more control over the lifetime of the object. Star 675. In 64-bit programs, the size of the pointer is 64 bits, and cannot be put into the int type, which remains 32-bit in almost all systems. @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. what does it mean to convert int to void* or vice versa? return ((void **) returnPtr);} /* Matrix() */. This will only compile if the destination type is long enough. Connect and share knowledge within a single location that is structured and easy to search. Making statements based on opinion; back them up with references or personal experience. Why does Mister Mxyzptlk need to have a weakness in the comics? property that any valid pointer to void can be converted to this type, use $(ARCHS_STANDARD_32_BIT) at Architecture instead of $(ARCHS_STANDARD). A pointer converted to an integer of sufficient size and back to the same pointer type is guaranteed to have its original value, otherwise the resulting pointer cannot be dereferenced safely ( the round-trip conversion in the opposite direction is not guaranteed [.]) By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. byte -> short -> char -> int -> long -> float -> double. The result is the same as implicit conversion from the enum's underlying type to the destination type. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? The text was updated successfully, but these errors were encountered: You signed in with another tab or window. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. If your standard library (even if it is not C99) happens to provide these types - use them. } SCAN_END_SINGLE(ATTR) Disconnect between goals and daily tasksIs it me, or the industry? The only alternative is really to take time and fix all 64-bit code issues, of which there may be some non-trivial issues. with ids being an array of ints and touch being a pointer. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Xcode 5 and iOS 7: Architecture and Valid architectures, xcode build error: Semantic issue cast from pointer to smaller type 'int' loses information, Issues in handling touches on subviews(uiviews) in UIScrollView, Architecture linking error after Xcode 5.1 upgrade, iOS 7.1 gives error after updating to Xcode 5.1, Linker error in Xcode 5.1 with cocos2d-x 3 beta 2. It generally takes place when in an expression more than one data type is present. Maybe you can try this too. This forum has migrated to Microsoft Q&A. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? this question. @BlueMoon Thanks a lot! Thanks for contributing an answer to Stack Overflow! ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Linear regulator thermal information missing in datasheet. Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. Why is this sentence from The Great Gatsby grammatical? For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. 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. I would create a structure and pass that as void* to pthread_create. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Setting a buffer of char* with intermediate casting to int*. Connect and share knowledge within a single location that is structured and easy to search. In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. If the value in a pointer is cast to a different type and it does not have the correct alignment for the new type, the behavior is undefined. You use the address-of operator & to do that. reinterpret_cast<void *>(42)). 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. 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. Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul There is no "correct" way to store a 64-bit pointer in an 32-bit integer. returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size);
This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. It's an int type guaranteed to be big enough to contain a pointer. Pull requests. If the destination type is bool, this is a boolean conversion (see below). LLNL's tutorial is bad and they should feel bad. 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! Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. void* -> integer -> void* rather than integer -> void* -> integer. 1. Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. Therefore, you need to change it to long long instead of long in windows for 64 bits. Visit Microsoft Q&A to post new questions. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. and how to print the thread id of 2d array argument? The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. 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. Casting arguments inside the function is a lot safer. tialized" "-Wno-format" "-Wno-incompatible-pointer-types" "-Werror" "-dM" "-U_MSC_VER" "-D_TIMESPEC_DEFINED" "-D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_SECURE_NO_WA actually no, as int my be a smaller type than a pointer ;-) But, of course with int64_t it works fine. You need to pass an actual pointer. Changing the type of ids would be the cleanest solution, but I decided against it when being confronted with this issue myself, as it only introduced a lot of issues with other code that is relying on ids being an int-array. If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] That could create all kinds of trouble. All character types are to be converted to an integer. How to use Slater Type Orbitals as a basis functions in matrix method correctly? Why do small African island nations perform better than African continental nations, considering democracy and human development? However the actual code in question contains an explicit c-style cast to int. Using Kolmogorov complexity to measure difficulty of problems? As a result of the integer division 3/2 we get the value 1, which is of the int type. The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS, AC Op-amp integrator with DC Gain Control in LTspice, Identify those arcade games from a 1983 Brazilian music video. a cast of which the programmer should be aware of what (s)he is doing. In such condition type conversion (type promotion) takes place to avoid loss of data. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? If the source type is bool, the value false is converted to zero and the value true is converted to the value one of the destination type (note that if the destination type is int, this is an integer promotion, not an integer conversion). rev2023.3.3.43278. "-I.." "-Iinclude\openflow" "-I..\include\openflow" "-Iinclude\openvswitch" "-I..\include\openvsw Is it suspicious or odd to stand by the gate of a GA airport watching the planes? Don't do that. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? 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. 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. (i.e. this way you won't get any warning. The subreddit for the C programming language, Press J to jump to the feed. ^~~~~~~~~~~~~~~~~~~~ Where does this (supposedly) Gibson quote come from? The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. This page has been accessed 1,655,678 times. To be honest, I think, clang is too restrictive here. Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] It is commonly called a pointer to T and its type is T*. } SCAN_END_SINGLE(ATTR) Where does this (supposedly) Gibson quote come from? Is it possible to create a concave light? Note the difference between the type casting of a variable and type casting of a pointer. As with all cast expressions, the result is: Two objects a and b are pointer-interconvertible if: static_cast may also be used to disambiguate function overloads by performing a function-to-pointer conversion to specific type, as in. It is done by the compiler on its own, without any external trigger from the user. So make sure you understand what you are doing! Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. rev2023.3.3.43278. What happens if you typecast as unsigned first? The value of float variable is= 37.75. I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. Just edited. On all of them int is 32bit, not 16bit. Floating-point conversions How to get the error message from the error code returned by GetLastError()? If you preorder a special airline meal (e.g. For example, the main thread could wait for all of the other threads to end before terminating. GitHub. This is known as implicit type casting or type promotion, compiler automatically converts smaller data type to larger data type. a is of type int[4], which can be implicitly cast to int* (ie, a pointer to an int) &a is of type int(*)[4] (ie: a pointer to an array of 4 ints). The cast back to int * is not, though. Identify those arcade games from a 1983 Brazilian music video, Relation between transaction data and transaction id, The difference between the phonemes /p/ and /b/ in Japanese. That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. You should perform type conversion based on 64bit build system because the type "int" supports only -32768 ~ 32768. (int) pthread_self() 64int48intuintptr_t (unsigned int) Can I tell police to wait and call a lawyer when served with a search warrant? The problem was there before, you just are being notified of it. If you preorder a special airline meal (e.g. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. For integer casts in specific, using into() signals that . 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. Connect and share knowledge within a single location that is structured and easy to search. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. Yeah, the tutorial is doing it wrong. Why does flowing off the end of a non-void function without returning a value not produce a compiler error? static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). 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. 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;. "After the incident", I started to be more careful not to trip over things. What is the correct method to cast an int to a void*? 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 394k 35 393 602 1 If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. Use #include to define it. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. how to cascade 2d int array to 2d void pointer array? Don't do that. Why is there a voltage on my HDMI and coaxial cables? The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. GitHub Skip to content Product Solutions Open Source Pricing Sign in Sign up smadaminov / ovs-dpdk-meson-issues Public Notifications Fork 1 Star 1 Code Issues 66 Pull requests Actions Projects 1 Security Insights New issue In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' Functions return bigint only if the parameter expression is a bigint data type. However, you are also casting the result of this operation to (void*). How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. what does it mean to convert int to void* or vice versa? LLNL's tutorial is bad and they should feel bad. Find centralized, trusted content and collaborate around the technologies you use most. For the remaining integral types, the result is the value of the enum if it can be represented by the target type and unspecified otherwise. If your standard library (even if it is not C99) happens to provide these types - use them. Remarks. The following behavior-changing defect reports were applied retroactively to previously published C++ standards. The program can be set in such a way to ask the user to inform the type of data and . Bulk update symbol size units from mm to map units in rule-based symbology. For a fairly recent compiler (that supports C99) you should not store or represent address as plain int value. Here is some piece of code where that error occur: /cocos2d-x-2.2.2/cocos2dx/platform/ios/EAGLView.mm:408:18: Cast from pointer to smaller type 'int' loses information. If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. You are right! Projects. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. p-util.c.obj "-c" ../lib/odp-util.c Connect and share knowledge within a single location that is structured and easy to search. What is the point of Thrower's Bandolier? converted back to pointer to void, and the result will compare equal C99 defines the types "intptr_t" and "uintptr_t" which do . This answer is incorrect for the reasons that have already been mentioned in the comment of, Error "Cast from pointer to smaller type 'int' loses information" in EAGLView.mm when update Xcode to 5.1 (5B130a), http://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models, http://stackoverflow.com/questions/18913906/xcode-5-and-ios-7-architecture-and-valid-architectures, How Intuit democratizes AI development across teams through reusability. Casting int to void* loses precision, and what is the solution in required cases, c++: cast from "const variable*" to "uint32" loses precision, Recovering from a blunder I made while emailing a professor, Relation between transaction data and transaction id. Infact I know several systems where that does not hold. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Implicit Type Conversion is also known as 'automatic type conversion'. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. I don't see how anything bad can happen . This is what the second warning is telling you. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. 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. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. : iPhone Retina 4-inch 64-bit) is selected. Does Counterspell prevent from any further spells being cast on a given turn? 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 Intuit democratizes AI development across teams through reusability. Update: Today, i download the latest version of cocos2d-x (cocos2d-x 2.2.3). A nit: in your version, the cast to void * is unnecessary. to your account, [87/252] Compiling C object lib/libopenvswitch.a.p/odp-util.c.obj 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. Put your define inside a bracket: without a problem. Usually that means the pointer is allocated with. Asking for help, clarification, or responding to other answers. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. How to use Slater Type Orbitals as a basis functions in matrix method correctly? You can use any other pointer, or you can use (size_t), which is 64 bits. Can Martian regolith be easily melted with microwaves? 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. When is casting void pointer needed in C? "because the type "int" supports only -32768 ~ 32768" This is not true for any modern desktop or mobile OS or any OS that is targeted by cocos2d-x. But the problem has still happened. Difficulties with estimation of epsilon-delta limit proof. Hence there is no loss in data. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). How can this new ban on drag possibly be considered constitutional? The proper way is to cast it to another pointer type. A cast converts an object or value from one type to another. Create an account to follow your favorite communities and start taking part in conversations. To learn more, see our tips on writing great answers. Returns a value of type new-type. Why do academics stay as adjuncts for years rather than move around? Netdev Archive on lore.kernel.org help / color / mirror / Atom feed * [mst-vhost:vhost 5/52] drivers/block/virtio_blk.c:539:21: warning: assignment to 'void *' from . @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. If the object expression refers or points to is actually a base class subobject of an object of type D, the result refers to the enclosing object of type D. Otherwise, the behavior is undefined: When the target type is bool (possibly cv-qualified), the result is false if the original value is zero and true for all other values. How Intuit democratizes AI development across teams through reusability. unsigned long call_fn = (unsigned long)FUNC; Sign up for a free GitHub account to open an issue and contact its maintainers and the community. SQL Server does not automatically promote . Thanks for pointing that out. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? Mutually exclusive execution using std::atomic? Replacing broken pins/legs on a DIP IC package, How to handle a hobby that makes income in US. ^~~~~~~~~~~~~~~~~~~~~ ", "? Find centralized, trusted content and collaborate around the technologies you use most. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? You could use this code, and it would do the same thing as casting ptr to (char*). 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. I assumed that gcc makes a 65536 out of my define, but I was wrong. rev2023.3.3.43278. Casting a pointer to void* and back is valid use of reinterpret_cast<>. Basically its a better version of (void *)i. But I'm nitpicking .. How do I force make/GCC to show me the commands? Evaluate integer expressions in a larger size before comparing or assigning to that size.Note that (time_+t)-1 also complies with INT31-C-EX3. warning C4311: 'type cast': pointer truncation from 'void *' to 'long' in ECPG test files. Yesterday, I updated Xcode to the newest version (5.1 (5B130a)) to compatible with iOS 7.1. How do I check if a string represents a number (float or int)? @jackdoe: It's a waste of human life to write code that "you may need in the future". Using indicator constraint with two variables. How can this new ban on drag possibly be considered constitutional? 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;
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