Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Windows has 32 bit long only on 64 bit as well. what happens when we typecast normal variable to void* or any pointer variable? I would create a structure and pass that as void* to pthread_create. FAILED: lib/libopenvswitch.a.p/odp-util.c.obj Why is this sentence from The Great Gatsby grammatical? What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. -1, Uggh. I cannot reverse my upvote of user384706's answer, but it's wrong. 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. This page has been accessed 1,655,678 times. An open (void) pointer can hold a pointer of any type. The problem just occur with Xcode 5.1. Are there tables of wastage rates for different fruit and veg? 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. ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' We have to pass address of the variable to the function because in function definition argument is pointer variable. 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. How to get the error message from the error code returned by GetLastError()? 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. Implementation-dependent. linux c-pthreads: problem with local variables. See also this documentation.. From and Into are generally intended to be lossless, infalliable conversions.as on the other hand can discard data and lead to bugs in some situations, for example casting a u64 to a usize may truncate the value on a 32-bit host. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. this question. Asking for help, clarification, or responding to other answers. I'm trying to create a void* from an int. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. 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. Does Counterspell prevent from any further spells being cast on a given turn? To learn more, see our tips on writing great answers. 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. The value of float variable is= 37.75. Where does this (supposedly) Gibson quote come from? Pull requests. Taking the above declarations of A, D, ch of the . 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. The cast back to int * is not, though. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' a cast of which the programmer should be aware of what (s)he is doing. How do I set, clear, and toggle a single bit? Don't do that. Connect and share knowledge within a single location that is structured and easy to search. The result is the same as implicit conversion from the enum's underlying type to the destination type. What you do here is undefined behavior, and undefined behavior of very practical sort. 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. 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. Casting a pointer to void* and back is valid use of reinterpret_cast<>. 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 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. 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. This is what the second warning is telling you. I recall there was a TreeNode(int) early on prior to 1.0 release I can't remember why I removed it, if I should felt it was easy enough to cast to (void*) or if it was because it created type inference conflict at the call site. To learn more, see our tips on writing great answers. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? reinterpret_cast<void *>(42)). (i.e. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. Why does Mister Mxyzptlk need to have a weakness in the comics? How to use Slater Type Orbitals as a basis functions in matrix method correctly? You can convert the values from one type to another explicitly using the cast operator as follows (type_name) expression Why do academics stay as adjuncts for years rather than move around? Half your pointer will be garbage. Apparently the clang version in Xcode 5.1 and above is more strict about potential 32bit vs. 64 bit incompatibilities in source code than older clang versions have been. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). Using indicator constraint with two variables. Why is there a voltage on my HDMI and coaxial cables? Bulk update symbol size units from mm to map units in rule-based symbology. Error while setting app icon and launch image in xcode 5.1. 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). There is absolutely not gurantee that sizeof(int) <= sizeof(void*). 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. Already on GitHub? But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. 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. All character types are to be converted to an integer. In this case, casting the pointer back to an integer is meaningless, because . C / C++ Forums on Bytes. The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. */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. use $(ARCHS_STANDARD_32_BIT) at Architecture instead of $(ARCHS_STANDARD). You are right! how to cascade 2d int array to 2d void pointer array? What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? LLNL's tutorial is bad and they should feel bad. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. Pd = Pa; Similarly, Pc may be type cast to type int and assigned the value Pa. 1. 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. Converting a void* to an int is non-portable way that may work or may not! Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. The subreddit for the C programming language, Press J to jump to the feed. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? equal to the original pointer: First you are using a define, which is not a variable. 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. property that any valid pointer to void can be converted to this type, 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. 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. Remarks. ^~~~~~~~~~~~~~~~~~~ Your first example is risky because you have to be very careful about the object lifetimes. Most answers just try to extract 32 useless bits out of the argument. Then i can continue compiling. 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. I am compiling this program in linux gcc compiler.. Casting int to void* loses precision, and what is the solution in required cases, c++: cast from "const variable*" to "uint32" loses precision, Recovering from a blunder I made while emailing a professor, Relation between transaction data and transaction id. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. 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. rev2023.3.3.43278. Thanks for contributing an answer to Stack Overflow! 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. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Xcode 5 and iOS 7: Architecture and Valid architectures, xcode build error: Semantic issue cast from pointer to smaller type 'int' loses information, Issues in handling touches on subviews(uiviews) in UIScrollView, Architecture linking error after Xcode 5.1 upgrade, iOS 7.1 gives error after updating to Xcode 5.1, Linker error in Xcode 5.1 with cocos2d-x 3 beta 2. Connect and share knowledge within a single location that is structured and easy to search. static_cast on the other hand should deny your stripping away the const qualifier. Well occasionally send you account related emails. p-util.c.obj "-c" ../lib/odp-util.c I need to cast the int from the first function so that I can use it as an argument for the second function. This is known as implicit type casting or type promotion, compiler automatically converts smaller data type to larger data type. GitHub Skip to content Product Solutions Open Source Pricing Sign in Sign up smadaminov / ovs-dpdk-meson-issues Public Notifications Fork 1 Star 1 Code Issues 66 Pull requests Actions Projects 1 Security Insights New issue Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. STR34-C. Not the answer you're looking for? I don't see how anything bad can happen . However the actual code in question contains an explicit c-style cast to int. If you preorder a special airline meal (e.g. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. @DietrichEpp can you explain what is race condition with using. The most general answer is - in no way. 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. Based on the design of this function, which modification is right. In C (int)b is called an explicit conversion, i.e. I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . What does casting to void* does when passing arguments to variadic functions? Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. My code is all over the place now but I appreciate you all helping me on my journey to mastery! Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? 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; Can I tell police to wait and call a lawyer when served with a search warrant? Thanks for contributing an answer to Stack Overflow! For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. Star 675. 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). And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. For a fairly recent compiler (that supports C99) you should not store or represent address as plain int value. If int is no larger than pointer to void then one way to store the value is by simply copying the bytes: int i . You may declare a const int variable and cast its reference to the void*. How create a simple program using threads in C? Find centralized, trusted content and collaborate around the technologies you use most. 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. */ >> -bool >> +enum conversion_safety >> unsafe_conversion_p (tree type, tree expr, bool . Noncompliant Code Example (memset())For historical reasons, certain C Standard functions accept an argument of type int and convert it to either unsigned char or plain char. Making statements based on opinion; back them up with references or personal experience. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. 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 proper way is to cast it to another pointer type. Find centralized, trusted content and collaborate around the technologies you use most. Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul As a result of the integer division 3/2 we get the value 1, which is of the int type. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. And then assign it to the double variable. Update: Today, i download the latest version of cocos2d-x (cocos2d-x 2.2.3). Note:You might receive a runtime exception if the pointer contains a value unsuitable for the context. this way you won't get any warning. A long long would not work for 32bit systems and a long would not work for 64 bit Windows (while 64bit Unix and Unix-like systems like OS X use the LP64 data model, in which a long is 64bit, 64bit Windows uses the LLP64 data model, in which a long has a size of 32bit (http://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models)). Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. that any valid pointer to void can be converted to this type, then Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? The main point is: a pointer has a platform dependent size. Thanks for contributing an answer to Stack Overflow! 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. rev2023.3.3.43278. 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. The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. You can use any other pointer, or you can use (size_t), which is 64 bits. In such a case the programmer can use a void pointer to point to the location of the unknown data type. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). "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 can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' This will only compile if the destination type is long enough. That's not a good idea if the original object (that was cast to void*) was an integer. 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. What is the correct method to cast an int to a void*? For integer casts in specific, using into() signals that . How can this new ban on drag possibly be considered constitutional? @BlueMoon Thanks a lot! Actions. casting from int to void* and back to int. AC Op-amp integrator with DC Gain Control in LTspice. I wish that you write those answer first than the explanation. "I think what you should do is actually pass the address of the variable to the function" Not necessarily.
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