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. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' @DietrichEpp can you explain what is race condition with using. The following program casts a double to an int. (int) pthread_self() 64int48intuintptr_t (unsigned int) Casting arguments inside the function is a lot safer. 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). Infact I know several systems where that does not hold. How to correctly cast a pointer to int in a 64-bit application? ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' to your account, [87/252] Compiling C object lib/libopenvswitch.a.p/odp-util.c.obj 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 way you won't get any warning. 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. Find centralized, trusted content and collaborate around the technologies you use most. C/C++ , Cerror: cast to 'void *' from smaller integer type 'int'. Pull requests. If you are going to pass the address you typically need to exert some more control over the lifetime of the object. Type casting is when you assign a value of one primitive data type to another type. Using an integer address (like &x) is probably wrong, indeed each modification you will execute on x will affect the pass behaviour. Then i can continue compiling. (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. A cast converts an object or value from one type to another. I have looked around and can't seem to find any information on how to do this. For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. 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. ^~~~~~~~~~~~~~~~~~~~~ Create an account to follow your favorite communities and start taking part in conversations. Making statements based on opinion; back them up with references or personal experience. 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). ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] windows meson: cast to smaller integer type 'unsigned long' from 'void *'. Connect and share knowledge within a single location that is structured and easy to search. 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. whether it was an actual problem is a different matter though. From that point on, you are dealing with 32 bits. A sane compiler may throw a warning on lines like this but by no way it should throw an error, because this code is NOT wrong, it is just potentially error-prone, but can be perfectly valid. This is why you got Error 1 C2036, from your post. Is a PhD visitor considered as a visiting scholar. Do new devs get fired if they can't solve a certain bug? 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. You need to pass an actual pointer. The program can be set in such a way to ask the user to inform the type of data and . Does a summoned creature play immediately after being summoned by a ready action? a cast of which the programmer should be aware of what (s)he is doing. The text was updated successfully, but these errors were encountered: You signed in with another tab or window. If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. Asking for help, clarification, or responding to other answers. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. 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. Your first example is risky because you have to be very careful about the object lifetimes. This will only compile if the destination type is long enough. Find centralized, trusted content and collaborate around the technologies you use most. Java Type Casting. Here, the Java first converts the int type data into the double type. I'm using cocos2d-x-2.2.2. And, most of these will not even work on gcc4. 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. for saving RAM), use union, and make sure, if the mem address is treated as an int only if you know it was last set as an int. On many systems, an 8-bit unsigned int can be stored at any address while an unsigned 32-bit int must be aligned on an address that is a multiple of 4. ), For those who are interested. 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. And in this context, it is very very very common to see programmers lazily type cast the. 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. I personally upvoted this answer because by it's first line of text it helped me to understand the reason of this strange error message and what am I, poor idiot, doing :D. Not valid on Windows 64 - long is still 32-bit but pointers are 64-bit. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. I'm trying to create a void* from an int. There is no "correct" way to store a 64-bit pointer in an 32-bit integer. rev2023.3.3.43278. Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. rev2023.3.3.43278. Note the difference between the type casting of a variable and type casting of a pointer. Not the answer you're looking for? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. Why is this sentence from The Great Gatsby grammatical? This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. Now, what happens when I run it with the thread sanitizer? It solved my problem too. 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. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ To learn more, see our tips on writing great answers. That's not a good idea if the original object (that was cast to void*) was an integer. But assuming that it is, as long as the caller and the callee agree, you can do that sort of thing. Therefore it is perfectly valid for the compiler to throw an error for a line like. rev2023.3.3.43278. 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. Such pointers can be stored in 32-bit data types (for instance, int, DWORD). By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. ^~~~~~~~~~~~~~~~~~~~ Hence there is no loss in data. and how to print the thread id of 2d array argument? Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. What is the purpose of non-series Shimano components? How do I force make/GCC to show me the commands? How do I align things in the following tabular environment? [] 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). . Safe downcast may be done with dynamic_cast. SCAN_PUT_ATTR(key, ATTR, skey, FUNC); In C (int)b is called an explicit conversion, i.e. Why do small African island nations perform better than African continental nations, considering democracy and human development? ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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. ^~~~~~~~~~~~~~~~~~~ Asking for help, clarification, or responding to other answers. Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. This is an old C callback mechanism so you can't change that. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. This page was last modified on 12 February 2023, at 18:25. C++ how to get the address stored in a void pointer? For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. 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; If you cast an int pointer int, you might get back a different integer. Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. 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 Linear regulator thermal information missing in datasheet. Don't do that. Replacing broken pins/legs on a DIP IC package, How to handle a hobby that makes income in US. Recovering from a blunder I made while emailing a professor. Use returnPtr[j] = (void *) ((long)ptr + i); ). 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]. /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. 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. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. You could use this code, and it would do the same thing as casting ptr to (char*). ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. you can just change architecture to support 32 bit compilation by all below in in Build Settings. Is pthread_join a must when using pthread in linux? Or, they are all wrong. Using Kolmogorov complexity to measure difficulty of problems? Have a question about this project? What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Windows has 32 bit long only on 64 bit as well. 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. I have a two functions, one that returns an int, and one that takes a const void* as an argument. Maybe you can try this too. 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. If you preorder a special airline meal (e.g. Making statements based on opinion; back them up with references or personal experience. use $(ARCHS_STANDARD_32_BIT) at Architecture instead of $(ARCHS_STANDARD). Find centralized, trusted content and collaborate around the technologies you use most. The text was updated successfully, but these errors were encountered: Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. Can I tell police to wait and call a lawyer when served with a search warrant? Thanks for contributing an answer to Stack Overflow! @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? Well occasionally send you account related emails. ^~~~~~~~~~~~~~~~~~~~ A nit: in your version, the cast to void * is unnecessary. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Setting a buffer of char* with intermediate casting to int*. "After the incident", I started to be more careful not to trip over things. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? ), Styling contours by colour and by line thickness in QGIS. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" This solution is in accordance with INT18-C. 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. Making statements based on opinion; back them up with references or personal experience. ", "!"? error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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. In a 64bit build a pointer is 64bit (contrary to a 32bit build, where it is 32bit), while an int is 32bit, so this assignment stores a 64bit value in a 32bit storage, which may result in a loss of information. This is what the second warning is telling you. If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. Mutually exclusive execution using std::atomic? 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. All float types are to be converted to double. Connect and share knowledge within a single location that is structured and easy to search. should we also have a diagnostic for the (presumed) user error? } SCAN_END_SINGLE(ATTR) 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). ../lib/odp-util.c:5601:9: note: expanded from macro 'SCAN_PUT' 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. 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. 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. rev2023.3.3.43278. Converting a void* to an int is non-portable way that may work or may not! My code is all over the place now but I appreciate you all helping me on my journey to mastery! 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). How to notate a grace note at the start of a bar with lilypond? It is purely a compile-time directive which instructs the compiler to treat expression as if it had . In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. Wrong. Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. byte -> short -> char -> int -> long -> float -> double. If the function had the correct signature you would not need to cast it explicitly. what happens when we typecast normal variable to void* or any pointer variable? Thanks for contributing an answer to Stack Overflow! 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. Yesterday, I updated Xcode to the newest version (5.1 (5B130a)) to compatible with iOS 7.1. */ >> -bool >> +enum conversion_safety >> unsafe_conversion_p (tree type, tree expr, bool . */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. I am an entry level C programmer. 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. The result is the same as implicit conversion from the enum's underlying type to the destination type. The only alternative is really to take time and fix all 64-bit code issues, of which there may be some non-trivial issues. 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 . It is commonly called a pointer to T and its type is T*. 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. Note:You might receive a runtime exception if the pointer contains a value unsuitable for the context. It's always a good practice to put your #define's in brackets to avoid such surprise. Does melting sea ices rises global sea level? 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; For example, the main thread could wait for all of the other threads to end before terminating. No idea how it amassed 27 upvotes?! I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? But I don't want to edit code in "EAGLView.mm" because it's a "library file". for (i=0, j=0; j Marilyn Hawrys Simons, Articles C