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As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. 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. I don't see how anything bad can happen . I'm trying to learn pthreads and thing that keeps bugging me is how do i really pass argument to the function. Otherwise, if the original pointer value points to an object a, and there is an object b of the . 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. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). This is what the second warning is telling you. I'm trying to create a void* from an int. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. Hence there is no loss in data. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Basically its a better version of (void *)i. Does melting sea ices rises global sea level? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. In the case of Widening Type Casting, the lower data type (having smaller size) is converted into the higher data type (having larger size). What you do here is undefined behavior, and undefined behavior of very practical sort. SCAN_PUT(ATTR, NULL); Now, what happens when I run it with the thread sanitizer? Linear regulator thermal information missing in datasheet. Disconnect between goals and daily tasksIs it me, or the industry? Actions. In such condition type conversion (type promotion) takes place to avoid loss of data. If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. The subreddit for the C programming language, Press J to jump to the feed. I agree passing a dynamically allocated pointer is fine (and I think the best way). Well occasionally send you account related emails. you can just change architecture to support 32 bit compilation by all below in in Build Settings. @Martin York: No, it doesn't depend on endiannness. You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : Converting one datatype into another is known as type casting or, type-conversion. This is why you got Error 1 C2036, from your post. use $(ARCHS_STANDARD_32_BIT) at Architecture instead of $(ARCHS_STANDARD). */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; Taking the above declarations of A, D, ch of the . 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. this way you won't get any warning. equal to the original pointer: First you are using a define, which is not a variable. and how to print the thread id of 2d array argument? Acidity of alcohols and basicity of amines. If you call your thread creation function like this, then the void* arriving inside of myFcn has the value of the int you put into it. reinterpret_cast<void *>(42)). This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. 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. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini But the problem has still happened. Then i can continue compiling. 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. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). "clang" "-Ilib\libopenvswitch.a.p" "-Ilib" "-I..\lib" "-I." This is an old C callback mechanism so you can't change that. How do I set, clear, and toggle a single bit? C/C++ , Cerror: cast to 'void *' from smaller integer type 'int'. LLNL's tutorial is bad and they should feel bad. Mutually exclusive execution using std::atomic? This is not a conversion at all. Connect and share knowledge within a single location that is structured and easy to search. You need to pass an actual pointer. If this is the data to a thread procedure, then you quite commonly want to pass by value. The proper way is to cast it to another pointer type. returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size); Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. You should perform type conversion based on 64bit build system because the type "int" supports only -32768 ~ 32768. Find centralized, trusted content and collaborate around the technologies you use most. Why does setupterm terminate the program? You are getting warnings due to casting a void* to a type of a different size. 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. 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). Such pointers can be stored in 32-bit data types (for instance, int, DWORD). Here is my code: I already tried (void*)M_TABLE_SIZE but then I get an error that I cannot use the * operator. Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. a cast of which the programmer should be aware of what (s)he is doing. @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? There is absolutely not gurantee that sizeof(int) <= sizeof(void*). 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. SCAN_PUT_ATTR(key, ATTR, skey, FUNC); converted back to pointer to void, and the result will compare equal Windows has 32 bit long only on 64 bit as well. By clicking Sign up for GitHub, you agree to our terms of service and Implementing From will result in the Into implementation but not vice-versa. 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 [.]) On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? It's always a good practice to put your #define's in brackets to avoid such surprise. 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. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? SQL Server does not automatically promote . Remembering to delete the pointer after use so that we don't leak. This is known as implicit type casting or type promotion, compiler automatically converts smaller data type to larger data type. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? My code is all over the place now but I appreciate you all helping me on my journey to mastery! 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. 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. ../lib/odp-util.c:5601:9: note: expanded from macro 'SCAN_PUT' Pd = Pa; Similarly, Pc may be type cast to type int and assigned the value Pa. 1. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. SCAN_PUT(ATTR, NULL); To avoid truncating your pointer, cast it to a type of identical size. Whats the grammar of "For those whose stories they are"? I am an entry level C programmer. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. @DavidHeffernan I rephrased that sentence a little. This answer is incorrect for the reasons that have already been mentioned in the comment of, Error "Cast from pointer to smaller type 'int' loses information" in EAGLView.mm when update Xcode to 5.1 (5B130a), http://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models, http://stackoverflow.com/questions/18913906/xcode-5-and-ios-7-architecture-and-valid-architectures, How Intuit democratizes AI development across teams through reusability. 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". Can I tell police to wait and call a lawyer when served with a search warrant? Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. what does it mean to convert int to void* or vice versa? He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. 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. Replacing broken pins/legs on a DIP IC package, How to handle a hobby that makes income in US. Most answers just try to extract 32 useless bits out of the argument. Asking for help, clarification, or responding to other answers. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. B language was designed to develop . Why did Ukraine abstain from the UNHRC vote on China? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. I have looked around and can't seem to find any information on how to do this. Thanks for contributing an answer to Stack Overflow! 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. You can fix this error by replacing this line of code. This solution is in accordance with INT18-C. B programing language is a language based on basic combined programming or a BCPL, and it is the precursor of the C programming language. Can Martian regolith be easily melted with microwaves? Thanks for contributing an answer to Stack Overflow! It is purely a compile-time directive which instructs the compiler to treat expression as if it had . How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. 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 From that point on, you are dealing with 32 bits. 1. then converted back to pointer to void, and the result will compare Sign up for a free GitHub account to open an issue and contact its maintainers and the community. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. how to cascade 2d int array to 2d void pointer array? */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. *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 . You can use any other pointer, or you can use (size_t), which is 64 bits. So,solution #3 works just fine. 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. byte -> short -> char -> int -> long -> float -> double. Why is this sentence from The Great Gatsby grammatical? Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. Narrowing Casting (manually) - converting a larger type to a . Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? 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; this way I convert an int to a void* which is much better than converting a void* to an int. 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. Infact I know several systems where that does not hold. I need to cast the int from the first function so that I can use it as an argument for the second function. A cast specifies a conversion from one type to another. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Before I update Xcode, my project still can build and run normally with all devices. Just edited. AC Op-amp integrator with DC Gain Control in LTspice. 10) A prvalue of type pointer to void (possibly cv-qualified) can be converted to pointer to any object type. You are getting warnings due to casting a void* to a type of a different size. How to use Slater Type Orbitals as a basis functions in matrix method correctly? ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' Bulk update symbol size units from mm to map units in rule-based symbology. 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. No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. 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). What is the difference between const int*, const int * const, and int const *? 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. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. Can Martian regolith be easily melted with microwaves? Is it possible to create a concave light? // OK: lvalue denoting the original d object, // UB: the b subobject is not a base class subobject, // 6. array-to-pointer followed by upcast, https://en.cppreference.com/mwiki/index.php?title=cpp/language/static_cast&oldid=147983, when converting a 'pointer to object' to 'pointer to, the conversion from floating-point values, the conversion from bit-fields to rvalue references, the conversion from integral or enumeration values to enumeration, the conversion from integral or enumeration values to, the conversion from a member of base class type to, a standard-layout class object with no data members, a non-standard-layout union object and a non-static data, for base-to-derived pointer conversions and, the conversion to enumeration types with fixed underlying type, a standard-layout class might have a non-pointer-interconvertible, If the underlying type is not fixed, the behavior is undefined if the value of, If the underlying type is fixed, the result is the same as, one is a union object and the other is a non-static data member of that object, or. The OP wanted to convert a pointer value to a int value, instead, most the answers, one way or the other, tried to wrongly convert the content of arg points to to a int value. Click to see the query in the CodeQL repository. ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' The text was updated successfully, but these errors were encountered: 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. I assumed that gcc makes a 65536 out of my define, but I was wrong. The calculated expression consists of two operations. A missing cast in the new fast > enumeration code. "After the incident", I started to be more careful not to trip over things. Not the answer you're looking for? Remarks. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? C99 defines the types "intptr_t" and "uintptr_t" which do . ncdu: What's going on with this second size column? It is done by the compiler on its own, without any external trigger from the user. And, most of these will not even work on gcc4. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. What is the purpose of non-series Shimano components? The most general answer is - in no way. } 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. Connect and share knowledge within a single location that is structured and easy to search. 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 eg. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. If it's anything like cocos2d-iphone v2.x and just based on this slice of code in a core class I wager it's safe to say that cocos2d-x 2.x also is not compatible with 64 bit code, and you can expect all kinds of issues (not just compile-time but also runtime). Have a question about this project? Thanks. How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? From the question I presume the OP does. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Recovering from a blunder I made while emailing a professor. Making statements based on opinion; back them up with references or personal experience. The only alternative is really to take time and fix all 64-bit code issues, of which there may be some non-trivial issues. Floating-point conversions This is flat out wrong. Why do academics stay as adjuncts for years rather than move around? Therefore, you need to change it to long long instead of long in windows for 64 bits. 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. rev2023.3.3.43278. Difficulties with estimation of epsilon-delta limit proof. Based on the design of this function, which modification is right. Can I tell police to wait and call a lawyer when served with a search warrant? Converts between types using a combination of implicit and user-defined conversions. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] 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. Already on GitHub? 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. Find centralized, trusted content and collaborate around the technologies you use most. C / C++ Forums on Bytes. 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. Why do small African island nations perform better than African continental nations, considering democracy and human development? 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; But I don't want to edit code in "EAGLView.mm" because it's a "library file". 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. To learn more, see our tips on writing great answers. Connect and share knowledge within a single location that is structured and easy to search. vegan) just to try it, does this inconvenience the caterers and staff? Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. 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. Connect and share knowledge within a single location that is structured and easy to search. Thanks for contributing an answer to Stack Overflow! 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.. 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. ^~~~~~~~~~~~~~~~~~~~ How do I align things in the following tabular environment? rev2023.3.3.43278. 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. 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;. You can only do this if you use a synchronization primitive to ensure that there is no race condition. @jackdoe: It's a waste of human life to write code that "you may need in the future". C++ how to get the address stored in a void pointer? Where does this (supposedly) Gibson quote come from? I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. How to notate a grace note at the start of a bar with lilypond? If the value is ever used as pointer again that will prove to be an extremely bad idea. 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. If you need to keep the returned address, just keep it as void*. All character types are to be converted to an integer. That could create all kinds of trouble. A nit: in your version, the cast to void * is unnecessary. You are right! Is it possible to create a concave light? If any, how can the original function works without errors if we just ignore the warning. Using indicator constraint with two variables. "I think what you should do is actually pass the address of the variable to the function" Not necessarily. If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. rev2023.3.3.43278. FAILED: lib/libopenvswitch.a.p/odp-util.c.obj Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? 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. Yesterday, I updated Xcode to the newest version (5.1 (5B130a)) to compatible with iOS 7.1. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. 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. The difference between a and &a is the type.