Not the answer you're looking for? What I am saying is that it would be safer to use new(5) rather than 5 and deal with it appropriately at the other end. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. 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. Actions. (void *)i Error: cast to 'void *' from smaller integer type 'int'. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. The following program casts a double to an int. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? 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], Minimising the environmental effects of my dyson brain. I cannot reverse my upvote of user384706's answer, but it's wrong. Replacing broken pins/legs on a DIP IC package, AC Op-amp integrator with DC Gain Control in LTspice. Thanks for contributing an answer to Stack Overflow! Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. What is the difference between const int*, const int * const, and int const *? SCAN_PUT_ATTR(key, ATTR, skey, FUNC); What is the purpose of non-series Shimano components? ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' For integer casts in specific, using into() signals that . a cast of which the programmer should be aware of what (s)he is doing. C / C++ Forums on Bytes. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Making statements based on opinion; back them up with references or personal experience. rev2023.3.3.43278. Does Counterspell prevent from any further spells being cast on a given turn? unsigned long call_fn = (unsigned long)FUNC; And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Why do small African island nations perform better than African continental nations, considering democracy and human development? ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' It's an int type guaranteed to be big enough to contain a pointer. 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 [.]) 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]. Bulk update symbol size units from mm to map units in rule-based symbology. error: cast from pointer to smaller type 'unsigned int' loses information. Terrible solution. Thanks. Typically, long or unsigned long is . It is commonly called a pointer to T and its type is T*. Bulk update symbol size units from mm to map units in rule-based symbology. You can only do this if you use a synchronization primitive to ensure that there is no race condition. Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. Why does flowing off the end of a non-void function without returning a value not produce a compiler error? "clang" "-Ilib\libopenvswitch.a.p" "-Ilib" "-I..\lib" "-I." 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. Not the answer you're looking for? 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. 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. 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; Don't do that. pthread create managing values generated in function (in c), Establishing TCP socket connection between PHP client and C server on Ubuntu. 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 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. Implementation-dependent. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. SCAN_PUT(ATTR, NULL); 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). Using printf with a pointer to float gives an error, Meaning of int (*) (int *) = 5 (or any integer value), Casting int to void* loses precision, and what is the solution in required cases, Acidity of alcohols and basicity of amines. ), For those who are interested. 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. What happens if you typecast as unsigned first? Such pointers can be stored in 32-bit data types (for instance, int, DWORD). How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. In such condition type conversion (type promotion) takes place to avoid loss of data. Bulk update symbol size units from mm to map units in rule-based symbology. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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: I am using size_t here, because it is always having the same size as a pointer, no matter the platform. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. Acidity of alcohols and basicity of amines. BUT converting a pointer to void* and back again is well supported (everywhere). If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. Find centralized, trusted content and collaborate around the technologies you use most. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. Maybe you can try this too. This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). A cast specifies a conversion from one type to another. Why is there a voltage on my HDMI and coaxial cables? Therefore it is perfectly valid for the compiler to throw an error for a line like. Noncompliant Code Example (memset())For historical reasons, certain C Standard functions accept an argument of type int and convert it to either unsigned char or plain char. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? Why do academics stay as adjuncts for years rather than move around? Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. How to convert a factor to integer\numeric without loss of information? This is not even remotely "the correct answer". C/C++ , Cerror: cast to 'void *' from smaller integer type 'int'. To learn more, see our tips on writing great answers. If you need to keep the returned address, just keep it as void*. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. If the original type is a void *, converting to an int may lose date on platforms where sizeof(void *) != sizeof(int) (which is true of LP64 programming model). -1, Uggh. @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. 1. A cast converts an object or value from one type to another. Making statements based on opinion; back them up with references or personal experience. All character types are to be converted to an integer. converted back to pointer to void, and the result will compare equal This is a fine way to pass integers to new pthreads, if that is what you need. In C (int)b is called an explicit conversion, i.e. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] This is not a conversion at all. I don't see how anything bad can happen . This allows you to reinterpret the void * as an int. What I am trying to emphasis that conversion from int to pointer and back again can be frough with problems as you move from platform to platform. Connect and share knowledge within a single location that is structured and easy to search. Implementing From will result in the Into implementation but not vice-versa. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). For the Nozomi from Shinagawa to Osaka, say on a Saturday afternoon, would tickets/seats typically be available - or would you need to book? On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. : iPhone Retina 4-inch 64-bit) is selected. So reinterpret_cast has casted it to long type and then static_cast safely casts long to int, if you are ready do truncte the data. Where does this (supposedly) Gibson quote come from? - the incident has nothing to do with me; can I use this this way? Is it possible to create a concave light? Functions return bigint only if the parameter expression is a bigint data type. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' Not the answer you're looking for? reinterpret_cast is a type of casting operator used in C++. And then assign it to the double variable. 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. How do I force make/GCC to show me the commands? To avoid truncating your pointer, cast it to a type of identical size. What video game is Charlie playing in Poker Face S01E07? The program can be set in such a way to ask the user to inform the type of data and . Converting one datatype into another is known as type casting or, type-conversion. 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. 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. And when assigning to a void pointer, all type information is lost. If the original pointer value represents an address of a byte in memory that does not satisfy the alignment requirement of the target type, then the resulting pointer value is unspecified. AC Op-amp integrator with DC Gain Control in LTspice. Have a question about this project? Thanks for contributing an answer to Stack Overflow! If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. @BlueMoon Thanks a lot! Therefore, you need to change it to long long instead of long in windows for 64 bits. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. And, most of these will not even work on gcc4. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The result is the same as implicit conversion from the enum's underlying type to the destination type. If we want to get the exact value of 7/5 then we need explicit casting from int to float: Example: int x=7, y=5; Don't do that. Does a summoned creature play immediately after being summoned by a ready action? So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. GitHub. Is it possible to create a concave light? What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? Keep in mind that thrArg should exist till the myFcn() uses it. How do I count the number of sentences in C using ". 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. If the sizes are different then endianess comes into play. 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. We have to pass address of the variable to the function because in function definition argument is pointer variable. Can Martian regolith be easily melted with microwaves? I think the solution 3> should be the correct one. It modifies >> Wconversion-real.c, Wconversion-real-integer.c and pr35635.c to be more >> specific > > If the patch passes existing tests, I'd be inclined to leave them > tests alone and add new ones that are specific to what this patch > changes. If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. You can convert the values from one type to another explicitly using the cast operator as follows (type_name) expression Thus as a result it may be less error prone to generate a pointer dynamcially and use that. warning C4311: 'type cast': pointer truncation from 'void *' to 'long' in ECPG test files. Narrowing Casting (manually) - converting a larger type to a . What is the point of Thrower's Bandolier? In simple example code like this it's very easy to convince yourself that there's no problem, but in more elaborate real-world scenarios it's very easy to make this mistake inadvertently. Click to see the query in the CodeQL repository. An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. Mutually exclusive execution using std::atomic? rev2023.3.3.43278. Wrong. But I'm nitpicking .. All float types are to be converted to double. 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. Is a PhD visitor considered as a visiting scholar. byte -> short -> char -> int -> long -> float -> double. Use #include to define it. Using Kolmogorov complexity to measure difficulty of problems? You are getting warnings due to casting a void* to a type of a different size. This will only compile if the destination type is long enough. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ to your account, [87/252] Compiling C object lib/libopenvswitch.a.p/odp-util.c.obj If the destination type is bool, this is a boolean conversion (see below). Just edited. Can I tell police to wait and call a lawyer when served with a search warrant? 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 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 do I align things in the following tabular environment? This page has been accessed 1,655,678 times. Does Counterspell prevent from any further spells being cast on a given turn? If any, how can the original function works without errors if we just ignore the warning. vegan) just to try it, does this inconvenience the caterers and staff? If int is no larger than pointer to void then one way to store the value is by simply copying the bytes: int i . This solution is in accordance with INT18-C. Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. Here, the Java first converts the int type data into the double type. Note:You might receive a runtime exception if the pointer contains a value unsuitable for the context. You can use any other pointer, or you can use (size_t), which is 64 bits. A missing cast in the new fast > enumeration code. 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. You need to pass an actual pointer. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. You may declare a const int variable and cast its reference to the void*. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. what does it mean to convert int to void* or vice versa? [that could be a TODO - not to delay solving the ICE]. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? SQL Server does not automatically promote . 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. 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. Asking for help, clarification, or responding to other answers. To learn more, see our tips on writing great answers. You think by casting it here that you are avoiding the problem! To subscribe to this RSS feed, copy and paste this URL into your RSS reader. LLNL's tutorial is bad and they should feel bad. A nit: in your version, the cast to void * is unnecessary. Notifications. Asking for help, clarification, or responding to other answers. Remembering to delete the pointer after use so that we don't leak. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. (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 c pthreads 4 10.3k 2 21 2015-06-05 Any help with this is appreciated. . Find centralized, trusted content and collaborate around the technologies you use most. Otherwise, if the original pointer value points to an object a, and there is an object b of the . I'm trying to learn pthreads and thing that keeps bugging me is how do i really pass argument to the function. Sign in An open (void) pointer can hold a pointer of any type. This forum has migrated to Microsoft Q&A. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. I assumed that gcc makes a 65536 out of my define, but I was wrong. Find centralized, trusted content and collaborate around the technologies you use most. Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. The main point is: a pointer has a platform dependent size. I am compiling this program in linux gcc compiler.. Whats the grammar of "For those whose stories they are"? The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. that any valid pointer to void can be converted to this type, then The value of float variable is= 37.75. Please help me compile Chez Scheme. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? The problem is not with casting, but with the target type loosing half of the pointer. 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. to the original pointer: The following type designates an unsigned integer type with the How Intuit democratizes AI development across teams through reusability. Cast characters to unsigned char before converting to larger integer sizes Created by Robert Seacord, last modified by Jill Britton on Oct 03, 2022 Signed character data must be converted to unsigned char before being assigned or converted to a larger signed type. Apparently the clang version in Xcode 5.1 and above is more strict about potential 32bit vs. 64 bit incompatibilities in source code than older clang versions have been. The subreddit for the C programming language, Press J to jump to the feed. ^~~~~~~~~~~~~~~~~~~~ Now, what happens when I run it with the thread sanitizer? How create a simple program using threads in C? To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. @Shahbaz you could but I will not suggest to a C newbie to use globals. Why does Mister Mxyzptlk need to have a weakness in the comics? . Here is my code: I already tried (void*)M_TABLE_SIZE but then I get an error that I cannot use the * operator. } SCAN_END_SINGLE(ATTR) "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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. (i.e. *PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type warning @ 2023-01-23 13:28 Hans de Goede 2023-01-23 13:56 ` Hans de Goede 0 siblings, 1 reply; 2+ messages in thread From: Hans de Goede @ 2023-01-23 13:28 UTC (permalink / raw) To: Mark Gross Cc: Hans de Goede, Andy Shevchenko, platform-driver-x86, kernel test robot Fix the following . */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. 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! 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; 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 . Hence there is no loss in data. ), Styling contours by colour and by line thickness in QGIS. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. To be honest, I think, clang is too restrictive here. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Asking for help, clarification, or responding to other answers. If you preorder a special airline meal (e.g. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. In the first example, the variable c1 of the char type is converted to a temporary variable of the int type, because the second operand in the division operation, the constant 2, is of the higher type int. 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. Already on GitHub? If the function had the correct signature you would not need to cast it explicitly. So make sure you understand what you are doing! this way you won't get any warning. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Setting a buffer of char* with intermediate casting to int*. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. 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. On all of them int is 32bit, not 16bit. How to notate a grace note at the start of a bar with lilypond? Thanks for contributing an answer to Stack Overflow! Then i can continue compiling. You are right! I'm trying to create a void* from an int. On many systems, an 8-bit unsigned int can be stored at any address while an unsigned 32-bit int must be aligned on an address that is a multiple of 4.
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