Implicit conversions - cppreference.com What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? [Solved] Properly casting a `void*` to an integer in C++ Where does this (supposedly) Gibson quote come from? The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. If your standard library (even if it is not C99) happens to provide these types - use them. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Setting a buffer of char* with intermediate casting to int*. Asking for help, clarification, or responding to other answers. AC Op-amp integrator with DC Gain Control in LTspice. 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;. windows meson: cast to smaller integer type 'unsigned long' from 'void I assumed that gcc makes a 65536 out of my define, but I was wrong. Use returnPtr[j] = (void *) ((long)ptr + i); ). But the problem has still happened. /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. Again, all of the answers above missed the point badly. this way I convert an int to a void* which is much better than converting a void* to an int. reinterpret_cast conversion - cppreference.com STR34-C. Cast characters to unsigned char before converting to larger 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. Not the answer you're looking for? "clang" "-Ilib\libopenvswitch.a.p" "-Ilib" "-I..\lib" "-I." casting from int to void* and back to int. static_cast on the other hand should deny your stripping away the const qualifier. Therefore it is perfectly valid for the compiler to throw an error for a line like. whether it was an actual problem is a different matter though. Such a downcast makes no runtime checks to ensure that the object's runtime type is actually D, and may only be used safely if this precondition is guaranteed by other means, such as when implementing static polymorphism. Since all pointers on 64-bit Windows are 64 bits, you are growing the data size from 32 bits backto 64 bits. Don't do that. Sign in [mst-vhost:vhost 5/52] drivers/block/virtio_blk.c:539:21: warning The text was updated successfully, but these errors were encountered: You signed in with another tab or window. The preprocesor absolutely will not perform arithmetic. What you do here is undefined behavior, and undefined behavior of very practical sort. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. Infact I know several systems where that does not hold. Visit Microsoft Q&A to post new questions. 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. C / C++ Forums on Bytes. Typecasting - Data Types - Language Basics - MQL4 Reference 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Use of Void pointers in C programming language 471,961 Members | 900 Online. Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. 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 Fork 63. This is not even remotely "the correct answer". If any, how can the original function works without errors if we just ignore the warning. Not the answer you're looking for? Does Counterspell prevent from any further spells being cast on a given turn? Keep in mind that thrArg should exist till the myFcn() uses it. The mapping in pointer<->integer casts is implementation defined, but the intent was that if the pointer type is large enough and isn't forcefully aligned (, But that's different. In 64-bit programs, the size of the pointer is 64 bits, and cannot be put into the int type, which remains 32-bit in almost all systems. There's no proper way to cast this to int in general case. Making statements based on opinion; back them up with references or personal experience. For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. Why did Ukraine abstain from the UNHRC vote on China? If pointers are 64 bits and ints are 32 bits, an int is too small to hold a pointer value. Casting a pointer to void* and back is valid use of reinterpret_cast<>. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. From what I read about casting in the C11 standard, my feeling is, that it is arguable to emit a warning on an explicit conversion. This returns the first 32 bits of the pointer which may be the top or the bottom depending on big versus little endian, as comment #2 said. An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. Connect and share knowledge within a single location that is structured and easy to search. No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. Converting one datatype into another is known as type casting or, type-conversion. How create a simple program using threads in C? Once you manage to make this cast, then what?! You are getting warnings due to casting a void* to a type of a different size. How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' Now, what happens when I run it with the thread sanitizer? Create an account to follow your favorite communities and start taking part in conversations. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. Here, the Java first converts the int type data into the double type. a is of type int[4], which can be implicitly cast to int* (ie, a pointer to an int) &a is of type int(*)[4] (ie: a pointer to an array of 4 ints). The most general answer is - in no way. For example, the main thread could wait for all of the other threads to end before terminating. Note the difference between the type casting of a variable and type casting of a pointer. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' [PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type warning Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. Does Counterspell prevent from any further spells being cast on a given turn? The calculated expression consists of two operations. LLNL's tutorial is bad and they should feel bad. What is the correct method to cast an int to a void*? Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. what does it mean to convert int to void* or vice versa? void* -> integer -> void* rather than integer -> void* -> integer. I need to cast the int from the first function so that I can use it as an argument for the second function. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. While working with Threads in C, I'm facing the warning, "warning: cast to pointer from integer of different size". Half your pointer will be garbage. The reinterpret_cast makes the int the size of a pointer and the warning will stop. How to use Slater Type Orbitals as a basis functions in matrix method correctly? Thanks for pointing that out. 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. From the question I presume the OP does. How to correctly cast a pointer to int in a 64-bit application? Why do small African island nations perform better than African continental nations, considering democracy and human development? } SCAN_END_SINGLE(ATTR) Type Casting in C Language with Examples - Dot Net Tutorials Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul casting from int to void* and back to int - C / C++ I'm trying to create a void* from an int. For integer casts in specific, using into() signals that . Just want to point out that the purpose of threads is, +1 absolutely true, but if you take you time to write struct {}, you can save a lot of troubles in the future when you want to receive/send more data then just an int. clang11 report error: cast to smaller integer type #82 - GitHub Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. Any help with this is appreciated. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Clang warnings for an invalid casting? - The FreeBSD Forums Windows has 32 bit long only on 64 bit as well. Why is there a voltage on my HDMI and coaxial cables? The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. 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. @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? However, you are also casting the result of this operation to (void*). 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. Can Martian regolith be easily melted with microwaves? Java Type Casting. Casting type void to uint8_t - Arduino Forum The preprocessor will replace your code by this: This is unlikely what you are trying to do. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SCAN_PUT_ATTR(mask, ATTR, smask, FUNC); reinterpret_cast is a type of casting operator used in C++. If the function had the correct signature you would not need to cast it explicitly. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Does melting sea ices rises global sea level? Do new devs get fired if they can't solve a certain bug? 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). Casting int to void* : r/C_Programming - reddit If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. Can anybody explain how to pass an integer to a function which receives (void * ) as a parameter? Note:You might receive a runtime exception if the pointer contains a value unsuitable for the context. 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". As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. 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. 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. Changing the type of ids would be the cleanest solution, but I decided against it when being confronted with this issue myself, as it only introduced a lot of issues with other code that is relying on ids being an int-array. If you 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). 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 . The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. How do I align things in the following tabular environment? 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 - the incident has nothing to do with me; can I use this this way? Narrowing Casting (manually) - converting a larger type to a . Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. ), Styling contours by colour and by line thickness in QGIS. C - Type Casting - tutorialspoint.com Why does flowing off the end of a non-void function without returning a value not produce a compiler error? x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. Pull requests. B programing language is a language based on basic combined programming or a BCPL, and it is the precursor of the C programming language. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? 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. 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. If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. How to correctly cast a pointer to int in a 64-bit application? Implementation-dependent. ), For those who are interested. Otherwise, if the original pointer value points to an object a, and there is an object b of the . 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. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. Replacing broken pins/legs on a DIP IC package, AC Op-amp integrator with DC Gain Control in LTspice. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. Replacing broken pins/legs on a DIP IC package, How to handle a hobby that makes income in US. Casting arguments inside the function is a lot safer. error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). 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; In such a case the programmer can use a void pointer to point to the location of the unknown data type. 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. How Intuit democratizes AI development across teams through reusability. 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. vegan) just to try it, does this inconvenience the caterers and staff? windows meson: cast to 'HANDLE' (aka 'void *') from smaller integer Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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.
