../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. this question. Visit Microsoft Q&A to post new questions. And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. void* -> integer -> void* rather than integer -> void* -> integer. Mutually exclusive execution using std::atomic? @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? this way you won't get any warning. How do I align things in the following tabular environment? You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. Using indicator constraint with two variables. I understood, but that would introduce dynamic memory and ugly lifetime issues (an object allocated by one thread must be freed by some other) - all just to pass an. You can only do this if you use a synchronization primitive to ensure that there is no race condition. An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. On all of them int is 32bit, not 16bit. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Most answers just try to extract 32 useless bits out of the argument. Is a PhD visitor considered as a visiting scholar. Projects. 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. Safe downcast may be done with dynamic_cast. 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. When is casting void pointer needed in C? 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. The following program casts a double to an int. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. If the function had the correct signature you would not need to cast it explicitly. vegan) just to try it, does this inconvenience the caterers and staff? But gcc always give me a warning, that i cannot cast an int to a void*. It is purely a compile-time directive which instructs the compiler to treat expression as if it had . If this is the data to a thread procedure, then you quite commonly want to pass by value. Does a summoned creature play immediately after being summoned by a ready action? 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". ^~~~~~~~~~~~~~~~~~~ ../lib/odp-util.c:5601:9: note: expanded from macro 'SCAN_PUT' */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. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. - the incident has nothing to do with me; can I use this this way? Does Counterspell prevent from any further spells being cast on a given turn? The problem was there before, you just are being notified of it. If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. Using Kolmogorov complexity to measure difficulty of problems? How to use Slater Type Orbitals as a basis functions in matrix method correctly? Remembering to delete the pointer after use so that we don't leak. The most general answer is - in no way. It generally takes place when in an expression more than one data type is present. To avoid truncating your pointer, cast it to a type of identical size. ERROR: incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int', error: cast to 'string' (aka 'char *') from smaller integer type 'int' [-Werror,-Wint-to-pointer-cast], error: incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int' C, warning: initialization of 'unsigned char' from 'uint8_t *' {aka 'unsigned char *'} makes integer from pointer without a cast [-Wint-conversion], Minimising the environmental effects of my dyson brain. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Create an account to follow your favorite communities and start taking part in conversations. Referring to N1570 7.20.1.4/p1 (Integer types capable of holding object pointers): The following type designates a signed integer type with the property If you cast an int pointer int, you might get back a different integer. How to use Slater Type Orbitals as a basis functions in matrix method correctly? 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. You are correct, but cocos actually only uses that address as a unique id. I need to convert the argument to an int for later use: The compiler (GCC version 4.2.4) returns the error: You can cast it to an intptr_t type. "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. You use the address-of operator & to do that. For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : This page has been accessed 1,655,678 times. Have a question about this project? I'm only guessing here, but I think what you are supposed to do is actually pass the address of the variable to the function. Type casting is when you assign a value of one primitive data type to another type. Making statements based on opinion; back them up with references or personal experience. 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. return ((void **) returnPtr);} /* Matrix() */. *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 . If any, how can the original function works without errors if we just ignore the warning. A pointer converted to an integer of sufficient size and back to the same pointer type is guaranteed to have its original value, otherwise the resulting pointer cannot be dereferenced safely ( the round-trip conversion in the opposite direction is not guaranteed [.]) 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. Issues. Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. vegan) just to try it, does this inconvenience the caterers and staff? As a result of the integer division 3/2 we get the value 1, which is of the int type. B programing language is a language based on basic combined programming or a BCPL, and it is the precursor of the C programming language. 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. (int) pthread_self() 64int48intuintptr_t (unsigned int) Why does flowing off the end of a non-void function without returning a value not produce a compiler error? 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. 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. @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. The program can be set in such a way to ask the user to inform the type of data and . Wrong. 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 . Just edited. 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). Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. 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 the object expression refers or points to is actually a base class subobject of an object of type D, the result refers to the enclosing object of type D. Otherwise, the behavior is undefined: When the target type is bool (possibly cv-qualified), the result is false if the original value is zero and true for all other values. windows meson: cast to smaller integer type 'unsigned long' from 'void *'. I need to cast the int from the first function so that I can use it as an argument for the second function. to your account, [87/252] Compiling C object lib/libopenvswitch.a.p/odp-util.c.obj Therefore it is perfectly valid for the compiler to throw an error for a line like. Getting Command /bin/sh failed with exit code 65 Error with Xcode 5.1 . Before I update Xcode, my project still can build and run normally with all devices. : iPhone Retina 4-inch 64-bit) is selected. On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. GitHub. You are right! Why do academics stay as adjuncts for years rather than move around? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. There is absolutely not gurantee that sizeof(int) <= sizeof(void*). So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. Such pointers can be stored in 32-bit data types (for instance, int, DWORD). How to convert a factor to integer\numeric without loss of information? Typically, long or unsigned long is . Bulk update symbol size units from mm to map units in rule-based symbology. Bulk update symbol size units from mm to map units in rule-based symbology. Why did Ukraine abstain from the UNHRC vote on China? 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 Converting a void* to an int is non-portable way that may work or may not! So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. Here, the Java first converts the int type data into the double type. Replacing broken pins/legs on a DIP IC package, AC Op-amp integrator with DC Gain Control in LTspice. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" And, most of these will not even work on gcc4. 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. 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). How do I set, clear, and toggle a single bit? By clicking Sign up for GitHub, you agree to our terms of service and How Intuit democratizes AI development across teams through reusability. The preprocesor absolutely will not perform arithmetic. This is why you got Error 1 C2036, from your post. Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. Fork 63. If the destination type is bool, this is a boolean conversion (see below). A missing cast in the new fast > enumeration code. How to get the error message from the error code returned by GetLastError()? @Shahbaz you could but I will not suggest to a C newbie to use globals. rev2023.3.3.43278. In the case of Widening Type Casting, the lower data type (having smaller size) is converted into the higher data type (having larger size). Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. 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]. rev2023.3.3.43278. Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. To be honest, I think, clang is too restrictive here. Why is there a voltage on my HDMI and coaxial cables? use $(ARCHS_STANDARD_32_BIT) at Architecture instead of $(ARCHS_STANDARD). The difference between a and &a is the type. A nit: in your version, the cast to void * is unnecessary. Usually that means the pointer is allocated with. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' This is what the second warning is telling you. You can fix this error by replacing this line of code. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. (i.e. 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. Does melting sea ices rises global sea level? I agree passing a dynamically allocated pointer is fine (and I think the best way). Is it suspicious or odd to stand by the gate of a GA airport watching the planes? Since all pointers on 64-bit Windows are 64 bits, you are growing the data size from 32 bits backto 64 bits. unsigned long call_fn = (unsigned long)FUNC; Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin? ", "? ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. XCode 5.1 is change all architecture to 64 bit. converted back to pointer to void, and the result will compare equal Offline ImPer Westermark over 11 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. Identify those arcade games from a 1983 Brazilian music video. 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. How create a simple program using threads in C? 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". Use returnPtr[j] = (void *) ((long)ptr + i); ). a cast of which the programmer should be aware of what (s)he is doing. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. Please help me compile Chez Scheme. What does casting to void* does when passing arguments to variadic functions? ncdu: What's going on with this second size column? What you do here is undefined behavior, and undefined behavior of very practical sort. So,solution #3 works just fine. How to notate a grace note at the start of a bar with lilypond? This is not even remotely "the correct answer". 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; Can Martian regolith be easily melted with microwaves? There's no proper way to cast this to int in general case. To learn more, see our tips on writing great answers. 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! 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. 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.