Implicit conversions - cppreference.com There is no "correct" way to store a 64-bit pointer in an 32-bit integer. (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 Identify those arcade games from a 1983 Brazilian music video. Can Martian regolith be easily melted with microwaves? ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' Disconnect between goals and daily tasksIs it me, or the industry? To learn more, see our tips on writing great answers. However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. 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). Type conversions - cplusplus.com Find centralized, trusted content and collaborate around the technologies you use most. This is flat out wrong. *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 . 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. that any valid pointer to void can be converted to this type, then Does Counterspell prevent from any further spells being cast on a given turn? He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. Does a summoned creature play immediately after being summoned by a ready action? If you are planning to use pthreads and you are planning to pass the pass function to pthread_create, you have to malloc/free the arguments you are planning to use (even if the threaded function just need a single int). 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. 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. ^~~~~~~~~~~~~~~~~~~~ @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. 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. Thanks for contributing an answer to Stack Overflow! Where does this (supposedly) Gibson quote come from? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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 . Connect and share knowledge within a single location that is structured and easy to search. 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. 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. reinterpret_cast conversion - cppreference.com Use of Void pointers in C programming language Using an integer address (like &x) is probably wrong, indeed each modification you will execute on x will affect the pass behaviour. long guarantees a pointer size on Linux on any machine. 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. I am an entry level C programmer. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? You are correct, but cocos actually only uses that address as a unique id. to your account, [87/252] Compiling C object lib/libopenvswitch.a.p/odp-util.c.obj Star 675. The preprocessor will replace your code by this: This is unlikely what you are trying to do. "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. Your first example is risky because you have to be very careful about the object lifetimes. SCAN_PUT(ATTR, NULL); Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. . Do new devs get fired if they can't solve a certain bug? You need to pass an actual pointer. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. INT31-C. Ensure that integer conversions do not result in lost or 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. Fork 63. For integer casts in specific, using into() signals that . ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' You should perform type conversion based on 64bit build system because the type "int" supports only -32768 ~ 32768. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. 10) A prvalue of type pointer to void (possibly cv-qualified) can be converted to pointer to any object type. How create a simple program using threads in C? Can Martian regolith be easily melted with microwaves? return ((void **) returnPtr);} /* Matrix() */. Thanks for contributing an answer to Stack Overflow! Again, all of the answers above missed the point badly. (int*)Pc = pa; After the execution of the above code all the three pointers, i.e., Pa, Pd, and Pc, point to the value 150. So make sure you understand what you are doing! 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". Asking for help, clarification, or responding to other answers. 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. This is a fine way to pass integers to new pthreads, if that is what you need. 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]. what does it mean to convert int to void* or vice versa? Find centralized, trusted content and collaborate around the technologies you use most. The program can be set in such a way to ask the user to inform the type of data and . 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). windows meson: cast to smaller integer type 'unsigned long' from 'void Here, the Java first converts the int type data into the double type. Casting and type conversions - C# Programming Guide Issues. On all of them int is 32bit, not 16bit. If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. If you are going to pass the address you typically need to exert some more control over the lifetime of the object. 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. [Solved] Properly casting a `void*` to an integer in C++ 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. 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. 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.. Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. Connect and share knowledge within a single location that is structured and easy to search. 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. Connect and share knowledge within a single location that is structured and easy to search. Why do small African island nations perform better than African continental nations, considering democracy and human development? When is casting void pointer needed in C? @DietrichEpp can you explain what is race condition with using. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. Why does Mister Mxyzptlk need to have a weakness in the comics? Usually that means the pointer is allocated with. Put your define inside a bracket: #define M_TABLE_SIZE (64*1024) Now, you can do: static const void* M_OFFSET = (void*) M_TABLE_SIZE; without a problem. In 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. We have to pass address of the variable to the function because in function definition argument is pointer variable. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. cast operators [edit] When an expression is used in the context where a value of a different type is expected, conversionmay occur: intn =1L;// expression 1L has type long, int is expectedn =2.1;// expression 2.1 has type double, int is expectedchar*p =malloc(10);// expression malloc(10) has type void*, char* is expected 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. then converted back to pointer to void, and the result will compare Implementation-dependent. If the destination type is bool, this is a boolean conversion (see below). 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). 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. Since gcc compiles that you are performing arithmetic between void* and an int (1024). ", "!"? SCAN_PUT(ATTR, NULL); How can this new ban on drag possibly be considered constitutional? The text was updated successfully, but these errors were encountered: You signed in with another tab or window. All float types are to be converted to double. 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. 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. windows meson: cast to 'HANDLE' (aka 'void *') from smaller integer To learn more, see our tips on writing great answers. c - Cast int to void* - Stack Overflow For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. 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. 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. Why is there a voltage on my HDMI and coaxial cables? I'm unfamiliar with XCode, but the solution should be something like follows: Most of the "solutions" above can lose part of the pointer address when casting to a smaller type. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. How do I check if a string represents a number (float or int)? 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. How to convert a factor to integer\numeric without loss of information? 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. Casting an open pointer to other pointer types and casting other pointer types to an open pointer does not result in a compile time error. My code is all over the place now but I appreciate you all helping me on my journey to mastery! [that could be a TODO - not to delay solving the ICE]. -1, Uggh. That's not a good idea if the original object (that was cast to void*) was an integer. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. cast to 'void *' from smaller integer type 'int' That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. C++ Tutorial => Conversion between pointer and integer } SCAN_END_SINGLE(ATTR) Typically, long or unsigned long is . Asking for help, clarification, or responding to other answers. Well occasionally send you account related emails. Re: [PATCH, PR 53001] Re: Patch to split out new warning flag for Compile error on Android ARM Issue #163 cisco/ChezScheme The problem was there before, you just are being notified of it. As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' If any, how can the original function works without errors if we just ignore the warning. Not the answer you're looking for? Linear regulator thermal information missing in datasheet. I cannot reverse my upvote of user384706's answer, but it's wrong. x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. Next, when doing pointer arithmetic, the addition operation will use the pointer's type to determine how many bytes to add to it when incrementing it. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Terrible solution. A cast converts an object or value from one type to another. Casting type void to uint8_t - Arduino Forum ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. static_cast conversion - cppreference.com In this case, casting the pointer back to an integer is meaningless, because . For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] Thanks for contributing an answer to Stack Overflow! Recovering from a blunder I made while emailing a professor. @jackdoe: It's a waste of human life to write code that "you may need in the future". LLNL's tutorial is bad and they should feel bad. C - Type Casting - tutorialspoint.com 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. "clang" "-Ilib\libopenvswitch.a.p" "-Ilib" "-I..\lib" "-I." BUT converting a pointer to void* and back again is well supported (everywhere). Thank you all for your feedback. I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. 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 Sign in What is the correct method to cast an int to a void*? Windows has 32 bit long only on 64 bit as well. The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. This allows you to reinterpret the void * as an int. Implicit Type Conversion in C with Examples - GeeksforGeeks By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Is a PhD visitor considered as a visiting scholar. And then assign it to the double variable. "After the incident", I started to be more careful not to trip over things.
SCAN_PUT_ATTR(key, ATTR, skey, FUNC); Whats the grammar of "For those whose stories they are"? "-I.." "-Iinclude\openflow" "-I..\include\openflow" "-Iinclude\openvswitch" "-I..\include\openvsw Already on GitHub? This is not even remotely "the correct answer". casting from int to void* and back to int. @DavidHeffernan I rephrased that sentence a little. 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
Using indicator constraint with two variables. cast to void *' from smaller integer type 'int You use the address-of operator & to do that. c - How to cast an integer to void pointer? - Stack Overflow How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? If pointers are 64 bits and ints are 32 bits, an int is too small to hold a pointer value. 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. this question. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Types - D Programming Language ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This is why you got Error 1 C2036, from your post. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. Converts between types using a combination of implicit and user-defined conversions. I have a two functions, one that returns an int, and one that takes a const void* as an argument. In such a case the programmer can use a void pointer to point to the location of the unknown data type. 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. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. I'm trying to create a void* from an int. This solution is in accordance with INT18-C. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. rev2023.3.3.43278. 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. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Or, they are all wrong. As a result of the integer division 3/2 we get the value 1, which is of the int type. If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. AC Op-amp integrator with DC Gain Control in LTspice.