vegan) just to try it, does this inconvenience the caterers and staff? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. 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. itch" "-I..\include\windows" "-Iinclude" "-I..\include" "-I..\datapath-windows\include" "-IC:\PTHREADS-BUILT\include" "-Xclang" "-fcolor-diagnostics" "-pipe" Implementation-dependent. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? What does casting to void* does when passing arguments to variadic functions? If your standard library (even if it is not C99) happens to provide these types - use them. 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. The difference between the phonemes /p/ and /b/ in Japanese. If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, You should be doing int x = *((int *)arg); You are casting from void * to int that is why you get the warning. Any help with this is appreciated. Why does Mister Mxyzptlk need to have a weakness in the comics? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. And, most of these will not even work on gcc4. [that could be a TODO - not to delay solving the ICE]. There's no proper way to cast this to int in general case. To be honest, I think, clang is too restrictive here. Star 675. Usually that means the pointer is allocated with. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. Windows has 32 bit long only on 64 bit as well. Yeah, the tutorial is doing it wrong. Why is there a voltage on my HDMI and coaxial cables? It solved my problem too. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. 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). error: cast from pointer to smaller type 'unsigned int' loses information. Whats the grammar of "For those whose stories they are"? Disconnect between goals and daily tasksIs it me, or the industry? 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. SCAN_PUT_ATTR(mask, ATTR, smask, FUNC); 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. Hence there is no loss in data. Your first example is risky because you have to be very careful about the object lifetimes. To cast such pointers to 32-bit types and vice versa special functions are used: void * Handle64ToHandle ( const void * POINTER_64 h ) void * POINTER_64 HandleToHandle64 ( const void *h ) long HandleToLong ( const void *h ) unsigned long HandleToUlong ( const void *h ) 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). rev2023.3.3.43278. 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 convert a factor to integer\numeric without loss of information? Is it possible to create a concave light? 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. Disconnect between goals and daily tasksIs it me, or the industry? Then i can continue compiling. But gcc always give me a warning, that i cannot cast an int to a void*. Wrong. And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. I cannot reverse my upvote of user384706's answer, but it's wrong. Instead of using a long cast, you should cast to size_t. Making statements based on opinion; back them up with references or personal experience. This page was last modified on 12 February 2023, at 18:25. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. C / C++ Forums on Bytes. I have a two functions, one that returns an int, and one that takes a const void* as an argument. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. Acidity of alcohols and basicity of amines. This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). this way I convert an int to a void* which is much better than converting a void* to an int. 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 STR34-C. For example, the main thread could wait for all of the other threads to end before terminating. Asking for help, clarification, or responding to other answers. Most answers just try to extract 32 useless bits out of the argument. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. 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. Press question mark to learn the rest of the keyboard shortcuts. Asking for help, clarification, or responding to other answers. 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. "-I.." "-Iinclude\openflow" "-I..\include\openflow" "-Iinclude\openvswitch" "-I..\include\openvsw There is absolutely not gurantee that sizeof(int) <= sizeof(void*). Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. Pull requests. A missing cast in the new fast > enumeration code. What is the point of Thrower's Bandolier? Update: Today, i download the latest version of cocos2d-x (cocos2d-x 2.2.3). use $(ARCHS_STANDARD_32_BIT) at Architecture instead of $(ARCHS_STANDARD). unsigned long call_fn = (unsigned long)FUNC; Does Counterspell prevent from any further spells being cast on a given turn? Thank you all for your feedback. Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. What is the purpose of non-series Shimano components? Properly casting a `void*` to an integer in C++ 24,193 Solution 1 I think using intptr_t is the correct intermediate here, since it's guaranteed to be large enough to contain the integral value of the void*, and once I have an integer value I can then truncate it without causing the compiler to complain. Thanks for pointing that out. Half your pointer will be garbage. All float types are to be converted to double. ^~~~~~~~~~~~~~~~~~~~ Is pthread_join a must when using pthread in linux? I'm trying to create a void* from an int. To learn more, see our tips on writing great answers. Yeah, the tutorial is doing it wrong. In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. How to use Slater Type Orbitals as a basis functions in matrix method correctly? 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. 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. 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. Is it possible to create a concave light? Api says this is how i should create thread: So if I want to pass an int what I think I should do is: The second example assumes that a pointer is wide enough to store an int. What you do here is undefined behavior, and undefined behavior of very practical sort. 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). Bulk update symbol size units from mm to map units in rule-based symbology. You can also convert values from one type to another explicitly using the cast operator (see Chapter 5 ): ( type_name) expression In the following example, the cast operator causes the division of one integer variable by another to be performed as a floating-point operation: int sum = 22, count = 5; double mean = (double)sum / count; property that any valid pointer to void can be converted to this type, What happens if you typecast as unsigned first? Why does flowing off the end of a non-void function without returning a value not produce a compiler error? ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' My code is all over the place now but I appreciate you all helping me on my journey to mastery! 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. This page has been accessed 1,655,678 times. Pd = Pa; Similarly, Pc may be type cast to type int and assigned the value Pa. 1. This is why you got Error 1 C2036, from your post. Projects. Why do small African island nations perform better than African continental nations, considering democracy and human development? 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. The text was updated successfully, but these errors were encountered: *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 . Therefore, you need to change it to long long instead of long in windows for 64 bits. How create a simple program using threads in C? The bigint data type is intended for use when integer values might exceed the range that is supported by the int data type.. bigint fits between smallmoney and int in the data type precedence chart.. However, you are also casting the result of this operation to (void*). I think the solution 3> should be the correct one. It is purely a compile-time directive which instructs the compiler to treat expression as if it had . "clang" "-Ilib\libopenvswitch.a.p" "-Ilib" "-I..\lib" "-I." Create an account to follow your favorite communities and start taking part in conversations. long guarantees a pointer size on Linux on any machine. Using an integer address (like &x) is probably wrong, indeed each modification you will execute on x will affect the pass behaviour. What is the difference between const int*, const int * const, and int const *? If int is no larger than pointer to void then one way to store the value is by simply copying the bytes: int i . SCAN_PUT_ATTR(key, ATTR, skey, FUNC); 10) A prvalue of type pointer to void (possibly cv-qualified) can be converted to pointer to any object type. For a fairly recent compiler (that supports C99) you should not store or represent address as plain int value. 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. Mutually exclusive execution using std::atomic? The subreddit for the C programming language, Press J to jump to the feed. @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. What is the point of Thrower's Bandolier? Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, error: cast from void* to int loses precision, cast to pointer from integer of different size, pthread code. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini How Intuit democratizes AI development across teams through reusability. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? B language was designed to develop . So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. Why does setupterm terminate the program? The correct answer is, if one does not mind losing data precision. Making statements based on opinion; back them up with references or personal experience. ), For those who are interested. converted back to pointer to void, and the result will compare equal As a result of the integer division 3/2 we get the value 1, which is of the int type. A cast converts an object or value from one type to another. Find centralized, trusted content and collaborate around the technologies you use most. to your account, [87/252] Compiling C object lib/libopenvswitch.a.p/odp-util.c.obj ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Find centralized, trusted content and collaborate around the technologies you use most. this question. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. Remarks. Any expression can be cast to type void (which means that the result of the expression is ignored), but it's not legal to cast an expression of type void to type int not least because the result of such a cast wouldn't make any sense. (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. Floating-point conversions C++ how to get the address stored in a void pointer? So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. SCAN_PUT(ATTR, NULL); Just edited. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? How Intuit democratizes AI development across teams through reusability. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. If the destination type is bool, this is a boolean conversion (see below). This allows you to reinterpret the void * as an int. From the question I presume the OP does. 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;. rev2023.3.3.43278. linux c-pthreads: problem with local variables. eg. Since gcc compiles that you are performing arithmetic between void* and an int (1024). warning C4311: 'type cast': pointer truncation from 'void *' to 'long' in ECPG test files. How can this new ban on drag possibly be considered constitutional? This is an old C callback mechanism so you can't change that. The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. It's an int type guaranteed to be big enough to contain a pointer. Mutually exclusive execution using std::atomic? What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? The proper way is to cast it to another pointer type. (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 FAILED: lib/libopenvswitch.a.p/odp-util.c.obj Connect and share knowledge within a single location that is structured and easy to search. 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. 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. 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. How to use Slater Type Orbitals as a basis functions in matrix method correctly? This is what the second warning is telling you. If that happens soon after the call to pthread_create() then you have a race condition, because there's a chance that the thread will attempt to read x's value after it's life has ended, which invokes undefined behavior. The most general answer is - in no way. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. 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. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Well occasionally send you account related emails. Bulk update symbol size units from mm to map units in rule-based symbology. Making statements based on opinion; back them up with references or personal experience. The result is the same as implicit conversion from the enum's underlying type to the destination type. ../lib/odp-util.c:5601:9: note: expanded from macro 'SCAN_PUT' 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. [] 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). ncdu: What's going on with this second size column? On all of them int is 32bit, not 16bit. Where does this (supposedly) Gibson quote come from? It was derived from the BCPL, and the name of the b language is possibly from the BCPL contraction. Since all pointers on 64-bit Windows are 64 bits, you are growing the data size from 32 bits backto 64 bits. How to notate a grace note at the start of a bar with lilypond? Difficulties with estimation of epsilon-delta limit proof. Maybe you can try this too. ../lib/odp-util.c:5489:33: note: expanded from macro 'SCAN_PUT_ATTR' Converts between types using a combination of implicit and user-defined conversions. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. rev2023.3.3.43278. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); What is the purpose of non-series Shimano components? How do I set, clear, and toggle a single bit? How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. Asking for help, clarification, or responding to other answers. 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 By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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 difference between a and &a is the type. You could use this code, and it would do the same thing as casting ptr to (char*). 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. 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" (. 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. This solution is in accordance with INT18-C. to the original pointer: The following type designates an unsigned integer type with the Whats the grammar of "For those whose stories they are"? actually no, as int my be a smaller type than a pointer ;-) But, of course with int64_t it works fine. void* -> integer -> void* rather than integer -> void* -> integer. If you preorder a special airline meal (e.g. I don't see how anything bad can happen . Narrowing Casting (manually) - converting a larger type to a . For integer casts in specific, using into() signals that . 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. with ids being an array of ints and touch being a pointer. Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. I agree passing a dynamically allocated pointer is fine (and I think the best way). Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. Recovering from a blunder I made while emailing a professor. We have to pass address of the variable to the function because in function definition argument is pointer variable. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] . 471,961 Members | 900 Online. 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. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Setting a buffer of char* with intermediate casting to int*. "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.
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