Is a PhD visitor considered as a visiting scholar. Making statements based on opinion; back them up with references or personal experience. A nit: in your version, the cast to void * is unnecessary. I wish that you write those answer first than the explanation. SQL Server does not automatically promote . Already on GitHub? Is it possible to create a concave light? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. to your account, [87/252] Compiling C object lib/libopenvswitch.a.p/odp-util.c.obj 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]. Half your pointer will be garbage. Disconnect between goals and daily tasksIs it me, or the industry? Fork 63. BUT converting a pointer to void* and back again is well supported (everywhere). then converted back to pointer to void, and the result will compare I think the solution 3> should be the correct one. 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; 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. ), Styling contours by colour and by line thickness in QGIS. The difference between a and &a is the type. warning C4311: 'type cast': pointer truncation from 'void *' to 'long' in ECPG test files. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? How to tell which packages are held back due to phased updates, 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. I am compiling this program in linux gcc compiler.. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. You are just making it bigger by tricking the compiler and the ABI. And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? The following program casts a double to an int. I'm trying to create a void* from an int. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. 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. What you do here is undefined behavior, and undefined behavior of very practical sort. 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. Whats the grammar of "For those whose stories they are"? But the problem has still happened. C++ how to get the address stored in a void pointer? 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). What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Just re-enforcing the old behavior of Xcode 5.0 and earlier versions, that already cut away parts of the address by casting it to int, won't introduce any new bugs and avoids the need to learn and understand lots of implementation-internal cocos code. Here, the Java first converts the int type data into the double type. To learn more, see our tips on writing great answers. As for the stack, I've written a few libraries using pthreds, thus I don't agree that what you describe "is quite often the case". The cast back to int * is not, though. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? The preprocessor will replace your code by this: This is unlikely what you are trying to do. (void *)i Error: cast to 'void *' from smaller integer type 'int'. 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. 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. that any valid pointer to void can be converted to this type, then @Xax: Here's a fixed version, without the race condition: gist.github.com/depp/241d6f839b799042c409, gist.github.com/depp/3f04508a88a114734195, How Intuit democratizes AI development across teams through reusability. 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. On all of them int is 32bit, not 16bit. rev2023.3.3.43278. rev2023.3.3.43278. 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. "-I.." "-Iinclude\openflow" "-I..\include\openflow" "-Iinclude\openvswitch" "-I..\include\openvsw What is the point of Thrower's Bandolier? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. lexborisov Modest Public. 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Here is my code: I already tried (void*)M_TABLE_SIZE but then I get an error that I cannot use the * operator. ../lib/odp-util.c:5601:9: note: expanded from macro 'SCAN_PUT' @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] What is the point of Thrower's Bandolier? this question. 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. Asking for help, clarification, or responding to other answers. Then I build my project, I get the error "Cast from pointer to smaller type 'int' loses information" in EAGLView.mm file (line 408) when 64-bit simulators (e.g. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' 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. } SCAN_END_SINGLE(ATTR) The calculated expression consists of two operations. Such pointers can be stored in 32-bit data types (for instance, int, DWORD). Why is there a voltage on my HDMI and coaxial cables? Why does setupterm terminate the program? A missing cast in the new fast > enumeration code. Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' (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 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). Is it possible to create a concave light? Can I tell police to wait and call a lawyer when served with a search warrant? How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. Mutually exclusive execution using std::atomic? 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. Note:You might receive a runtime exception if the pointer contains a value unsuitable for the context. 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. "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. The problem just occur with Xcode 5.1. Connect and share knowledge within a single location that is structured and easy to search. You can fix this error by replacing this line of code. How can this new ban on drag possibly be considered constitutional? How do I force make/GCC to show me the commands? 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. Find centralized, trusted content and collaborate around the technologies you use most. If the destination type is bool, this is a boolean conversion (see below). Type casting is when you assign a value of one primitive data type to another type. Difficulties with estimation of epsilon-delta limit proof. I'm trying to learn pthreads and thing that keeps bugging me is how do i really pass argument to the function. So you know you can cast it back like this. *sound/soc/codecs/tlv320aic32x4.c:1202:18: warning: cast to smaller integer type 'enum aic32x4_type' from 'void *' @ 2022-04-22 9:48 kernel test robot 0 siblings, 0 . */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. Well occasionally send you account related emails. 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. What does it mean to convert int to void* or vice versa? Thanks for contributing an answer to Stack Overflow! Returns a value of type new-type. ), For those who are interested. Why do small African island nations perform better than African continental nations, considering democracy and human development? 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 subscribe to this RSS feed, copy and paste this URL into your RSS reader. Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. All character types are to be converted to an integer. How do I check if a string represents a number (float or int)? property that any valid pointer to void can be converted to this type, Projects. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. FAILED: lib/libopenvswitch.a.p/odp-util.c.obj Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. how to cascade 2d int array to 2d void pointer array? B programing language is a language based on basic combined programming or a BCPL, and it is the precursor of the C programming language. Floating-point conversions How to use Slater Type Orbitals as a basis functions in matrix method correctly? If you need to keep the returned address, just keep it as void*. Acidity of alcohols and basicity of amines. what does it mean to convert int to void* or vice versa? Asking for help, clarification, or responding to other answers. I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . This page has been accessed 1,655,678 times. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. Connect and share knowledge within a single location that is structured and easy to search. From that point on, you are dealing with 32 bits. actually no, as int my be a smaller type than a pointer ;-) But, of course with int64_t it works fine. The text was updated successfully, but these errors were encountered: linux c-pthreads: problem with local variables. Find centralized, trusted content and collaborate around the technologies you use most. Not the answer you're looking for? Where does this (supposedly) Gibson quote come from? Find centralized, trusted content and collaborate around the technologies you use most. You are right! 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. 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. If this is the data to a thread procedure, then you quite commonly want to pass by value. If the sizes are different then endianess comes into play. C99 defines the types "intptr_t" and "uintptr_t" which do . I agree passing a dynamically allocated pointer is fine (and I think the best way). The following behavior-changing defect reports were applied retroactively to previously published C++ standards. Not the answer you're looking for? You use the address-of operator & to do that. If you cast an int pointer int, you might get back a different integer. It is commonly called a pointer to T and its type is T*. If your standard library (even if it is not C99) happens to provide these types - use them. But gcc always give me a warning, that i cannot cast an int to a void*. 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. Yesterday, I updated Xcode to the newest version (5.1 (5B130a)) to compatible with iOS 7.1. 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. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. The correct answer is, if one does not mind losing data precision. windows meson: cast to smaller integer type 'unsigned long' from 'void *'. Functions return bigint only if the parameter expression is a bigint data type. ", "? Thanks for contributing an answer to Stack Overflow! Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); I need to cast the int from the first function so that I can use it as an argument for the second function. 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. 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; Converting one datatype into another is known as type casting or, type-conversion. 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 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. byte -> short -> char -> int -> long -> float -> double. 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. I assumed that gcc makes a 65536 out of my define, but I was wrong. 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. 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 you won't get any warning. } SCAN_END_SINGLE(ATTR) For integer casts in specific, using into() signals that . 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! Remembering to delete the pointer after use so that we don't leak. 1. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. Safe downcast may be done with dynamic_cast. RNINGS" "-D_CRT_SECURE_NO_DEPRECATE" -MD -MQ lib/libopenvswitch.a.p/odp-util.c.obj -MF "lib\libopenvswitch.a.p\odp-util.c.obj.d" -o lib/libopenvswitch.a.p/od How to notate a grace note at the start of a bar with lilypond? 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. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Why is there a voltage on my HDMI and coaxial cables? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Infact I know several systems where that does not hold. To learn more, see our tips on writing great answers. @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. Therefore, you need to change it to long long instead of long in windows for 64 bits. There is absolutely not gurantee that sizeof(int) <= sizeof(void*). To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Connect and share knowledge within a single location that is structured and easy to search. There exist two main syntaxes for generic type-casting: functional and c-like: 1 2 3 4 double x = 10.3; int y; y = int (x); // functional notation y = (int) x; // c-like cast notation The functionality of these generic forms of type-casting is enough for most needs with fundamental data types. The problem is not with casting, but with the target type loosing half of the pointer. You are getting warnings due to casting a void* to a type of a different size. An open (void) pointer can hold a pointer of any type. converted back to pointer to void, and the result will compare equal Find centralized, trusted content and collaborate around the technologies you use most. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Using Kolmogorov complexity to measure difficulty of problems? */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. cast to 'double *' from smaller integer type 'unsigned int' The C compiler is gcc, clang version 3.9.1, target aarch64--linux-android, thread model posix. Typically, long or unsigned long is . The proper way is to cast it to another pointer type. Then i can continue compiling. for (i=0, j=0; j Are Bobby Flay's Parents Alive, Articles C