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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). What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? 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 But I don't want to edit code in "EAGLView.mm" because it's a "library file". ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. Otherwise, if the original pointer value points to an object a, and there is an object b of the . error: cast from pointer to smaller type 'unsigned int' loses information. C99 defines the types "intptr_t" and "uintptr_t" which do . Implicit Type Conversion is also known as 'automatic type conversion'. This is an old C callback mechanism so you can't change that. When is casting void pointer needed in C? There is absolutely not gurantee that sizeof(int) <= sizeof(void*). On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. The text was updated successfully, but these errors were encountered: You signed in with another tab or window. Acidity of alcohols and basicity of amines. return ((void **) returnPtr);} /* Matrix() */. 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 . long guarantees a pointer size on Linux on any machine. Why do small African island nations perform better than African continental nations, considering democracy and human development? static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). Thanks for contributing an answer to Stack Overflow! what does it mean to convert int to void* or vice versa? If the function had the correct signature you would not need to cast it explicitly. How to get the error message from the error code returned by GetLastError()? 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. Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Can I tell police to wait and call a lawyer when served with a search warrant? Why does setupterm terminate the program? Implementing From will result in the Into implementation but not vice-versa. ^~~~~~~~~~~~~~~~~~~~ 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. 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. eg. On all of them int is 32bit, not 16bit. This is a fine way to pass integers to new pthreads, if that is what you need. Does a summoned creature play immediately after being summoned by a ready action? ", "!"? What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. You are getting warnings due to casting a void* to a type of a different size. 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. And then assign it to the double variable. If you cast an int pointer int, you might get back a different integer. 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. Using Kolmogorov complexity to measure difficulty of problems? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Infact I know several systems where that does not hold. A void pointer can be really useful if the programmer is not sure about the data type of data inputted by the end user. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. ^~~~~~~~~~~~~~~~~~~~~ The following behavior-changing defect reports were applied retroactively to previously published C++ standards. For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. For example, the main thread could wait for all of the other threads to end before terminating. Remarks. Any help with this is appreciated. 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). It is done by the compiler on its own, without any external trigger from the user. It's always a good practice to put your #define's in brackets to avoid such surprise. Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. 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, error: cast from void* to int loses precision, cast to pointer from integer of different size, pthread code. "After the incident", I started to be more careful not to trip over things. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. Disconnect between goals and daily tasksIs it me, or the industry? How to notate a grace note at the start of a bar with lilypond? BUT converting a pointer to void* and back again is well supported (everywhere). A nit: in your version, the cast to void * is unnecessary. Safe downcast may be done with dynamic_cast. (int) pthread_self() 64int48intuintptr_t (unsigned int) } SCAN_END_SINGLE(ATTR) 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. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? Are there tables of wastage rates for different fruit and veg? You should perform type conversion based on 64bit build system because the type "int" supports only -32768 ~ 32768. @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? 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; A missing cast in the new fast > enumeration code. this way you won't get any warning. Why is there a voltage on my HDMI and coaxial cables? Thanks for contributing an answer to Stack Overflow! If you preorder a special airline meal (e.g. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Find centralized, trusted content and collaborate around the technologies you use most. 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]. The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. Using an integer address (like &x) is probably wrong, indeed each modification you will execute on x will affect the pass behaviour. Have a question about this project? In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. with ids being an array of ints and touch being a pointer. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. Projects. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. If any, how can the original function works without errors if we just ignore the warning. 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 difference between a and &a is the type. A nit: in your version, the cast to void * is unnecessary. You are getting warnings due to casting a void* to a type of a different size. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. (i.e. 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. (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. 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. You can fix this error by replacing this line of code. What you do here is undefined behavior, and undefined behavior of very practical sort. The difference between the phonemes /p/ and /b/ in Japanese. Is it possible to create a concave light? Identify those arcade games from a 1983 Brazilian music video. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Usually that means the pointer is allocated with. The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. Getting Command /bin/sh failed with exit code 65 Error with Xcode 5.1 . C/C++ , Cerror: cast to 'void *' from smaller integer type 'int'. 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). Don't do that. B programing language is a language based on basic combined programming or a BCPL, and it is the precursor of the C programming language. What is the correct method to cast an int to a void*? Narrowing Casting (manually) - converting a larger type to a . should we also have a diagnostic for the (presumed) user error? I'm using cocos2d-x-2.2.2. equal to the original pointer: First you are using a define, which is not a variable. Do new devs get fired if they can't solve a certain bug? He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. Find centralized, trusted content and collaborate around the technologies you use most. Put your define inside a bracket: without a problem. a cast of which the programmer should be aware of what (s)he is doing. 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. You can use any other pointer, or you can use (size_t), which is 64 bits. 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. this question. (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 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). 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. 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. There's probably little you can do except look or hope for a fixed 2.x version or upgrade to 3.x (I would assume it's 64-bit safe but this is just a guess, do research this issue before you upgrade). 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, the Java first converts the int type data into the double type. SCAN_PUT(ATTR, NULL); It's an int type guaranteed to be big enough to contain a pointer. I cannot reverse my upvote of user384706's answer, but it's wrong. */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; How do I count the number of sentences in C using ". How do I align things in the following tabular environment? This explicit cast clearly tells the compiler "Shut up, I know that this code does not look correct, but I do know what I am doing". As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? Making statements based on opinion; back them up with references or personal experience. Windows has 32 bit long only on 64 bit as well. Update: Today, i download the latest version of cocos2d-x (cocos2d-x 2.2.3). 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. And when assigning to a void pointer, all type information is lost. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. - the incident has nothing to do with me; can I use this this way? and how to print the thread id of 2d array argument? Floating-point conversions If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. rev2023.3.3.43278. I don't see how anything bad can happen . Yeah, the tutorial is doing it wrong. use $(ARCHS_STANDARD_32_BIT) at Architecture instead of $(ARCHS_STANDARD). Pd = Pa; Similarly, Pc may be type cast to type int and assigned the value Pa. 1. Half your pointer will be garbage. How do I force make/GCC to show me the commands? 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. Casting arguments inside the function is a lot safer. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' 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. The problem was there before, you just are being notified of it. To learn more, see our tips on writing great answers. Making statements based on opinion; back them up with references or personal experience. Making statements based on opinion; back them up with references or personal experience. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? This is why you got Error 1 C2036, from your post. Your first example is risky because you have to be very careful about the object lifetimes. Sign in 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. 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 rev2023.3.3.43278. Keep in mind that thrArg should exist till the myFcn() uses it. Note the difference between the type casting of a variable and type casting of a pointer. 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. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' To learn more, see our tips on writing great answers. Why is this sentence from The Great Gatsby grammatical? 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. Recovering from a blunder I made while emailing a professor. 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. this way you won't get any warning. Since gcc compiles that you are performing arithmetic between void* and an int (1024). Star 675. Can Martian regolith be easily melted with microwaves? static_cast on the other hand should deny your stripping away the const qualifier. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. How do I check if a string represents a number (float or int)? @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. (void *)i Error: cast to 'void *' from smaller integer type 'int'. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. Typically, long or unsigned long is . 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. Can Martian regolith be easily melted with microwaves? Mutually exclusive execution using std::atomic? But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. 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 cast back to int * is not, though. 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. tialized" "-Wno-format" "-Wno-incompatible-pointer-types" "-Werror" "-dM" "-U_MSC_VER" "-D_TIMESPEC_DEFINED" "-D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_SECURE_NO_WA The result is the same as implicit conversion from the enum's underlying type to the destination type. To learn more, see our tips on writing great answers. What does casting to void* does when passing arguments to variadic functions? ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] But the problem has still happened. SCAN_PUT_ATTR(key, ATTR, skey, FUNC); SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); "clang" "-Ilib\libopenvswitch.a.p" "-Ilib" "-I..\lib" "-I." Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. 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. Just edited. Does Counterspell prevent from any further spells being cast on a given turn? So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? 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 Most answers just try to extract 32 useless bits out of the argument. The preprocesor absolutely will not perform arithmetic. You can only do this if you use a synchronization primitive to ensure that there is no race condition. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. There's no proper way to cast this to int in general case. How to convert a factor to integer\numeric without loss of information? The correct answer is, if one does not mind losing data precision. You are right! 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. Converting a void* to an int is non-portable way that may work or may not! For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. Find centralized, trusted content and collaborate around the technologies you use most. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? 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.. If the sizes are different then endianess comes into play. Notifications. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. The most general answer is - in no way. How to correctly cast a pointer to int in a 64-bit application? @BlueMoon Thanks a lot! 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. This allows you to reinterpret the void * as an int. From the question I presume the OP does. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Press question mark to learn the rest of the keyboard shortcuts. Why does Mister Mxyzptlk need to have a weakness in the comics? Yesterday, I updated Xcode to the newest version (5.1 (5B130a)) to compatible with iOS 7.1. ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' 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 am an entry level C programmer. Fork 63. If you are going to pass the address you typically need to exert some more control over the lifetime of the object. you can just change architecture to support 32 bit compilation by all below in in Build Settings. The only alternative is really to take time and fix all 64-bit code issues, of which there may be some non-trivial issues. If the destination type is bool, this is a boolean conversion (see below). The proper way is to cast it to another pointer type. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? To learn more, see our tips on writing great answers. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. } SCAN_END_SINGLE(ATTR) privacy statement. windows meson: cast to smaller integer type 'unsigned long' from 'void *'. Don't do that. In C (int)b is called an explicit conversion, i.e. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); casting from int to void* and back to int. to your account, [87/252] Compiling C object lib/libopenvswitch.a.p/odp-util.c.obj Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. In this case, casting the pointer back to an integer is meaningless, because . But then you need to cast your arguments inside your thread function which is quite unsafe cf. 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). Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? */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.