You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. Thanks for contributing an answer to Stack Overflow! . -1, Uggh. This page has been accessed 1,655,678 times. Bulk update symbol size units from mm to map units in rule-based symbology. In simple example code like this it's very easy to convince yourself that there's no problem, but in more elaborate real-world scenarios it's very easy to make this mistake inadvertently. If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. // 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. Identify those arcade games from a 1983 Brazilian music video, Relation between transaction data and transaction id, The difference between the phonemes /p/ and /b/ in Japanese. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? 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. You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : Windows has 32 bit long only on 64 bit as well. "I think what you should do is actually pass the address of the variable to the function" Not necessarily. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. Why is this sentence from The Great Gatsby grammatical? Why does setupterm terminate the program? This is what the second warning is telling you. This is not a conversion at all. Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. Wrong. Why is there a voltage on my HDMI and coaxial cables? 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). 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. What is the purpose of non-series Shimano components? Why is there a voltage on my HDMI and coaxial cables? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Mutually exclusive execution using std::atomic? 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. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. with ids being an array of ints and touch being a pointer. 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. LLNL's tutorial is bad and they should feel bad. 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. The problem was there before, you just are being notified of it. You think by casting it here that you are avoiding the problem! pthread passes the argument as a void*. Connect and share knowledge within a single location that is structured and easy to search. Again, all of the answers above missed the point badly. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Find centralized, trusted content and collaborate around the technologies you use most. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. this question. @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? The compiler issues the "cast from integer to pointer of different size" warning whenever the value of an integer is converted to a pointer, especially when the memory allocated to a pointer is smaller than the memory allocated to an integer data type. This is why you got Error 1 C2036, from your post. 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. Here, the Java first converts the int type data into the double type. 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. Java Type Casting. Here is my code: I already tried (void*)M_TABLE_SIZE but then I get an error that I cannot use the * operator. For the Nozomi from Shinagawa to Osaka, say on a Saturday afternoon, would tickets/seats typically be available - or would you need to book? I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . Why is there a voltage on my HDMI and coaxial cables? what does it mean to convert int to void* or vice versa? BUT converting a pointer to void* and back again is well supported (everywhere). error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. void* -> integer -> void* rather than integer -> void* -> integer. If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. If you preorder a special airline meal (e.g. ^~~~~~~~~~~~~~~~~~~ My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? If your standard library (even if it is not C99) happens to provide these types - use them. 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 The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] It was derived from the BCPL, and the name of the b language is possibly from the BCPL contraction. How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. converted back to pointer to void, and the result will compare equal Find centralized, trusted content and collaborate around the technologies you use most. Pull requests. then converted back to pointer to void, and the result will compare Press question mark to learn the rest of the keyboard shortcuts. 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. The preprocesor absolutely will not perform arithmetic. Can I tell police to wait and call a lawyer when served with a search warrant? rev2023.3.3.43278. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. Bulk update symbol size units from mm to map units in rule-based symbology. A cast specifies a conversion from one type to another. It is easier to understand and write than any other assembly language. If you need to keep the returned address, just keep it as void*. ^~~~~~~~~~~~~~~~~~~~ Already on GitHub? 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". GitHub. Based on the design of this function, which modification is right. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. 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; You can fix this error by replacing this line of code. Projects. 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. When is casting void pointer needed in C? *PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type warning @ 2023-01-23 13:28 Hans de Goede 2023-01-23 13:56 ` Hans de Goede 0 siblings, 1 reply; 2+ messages in thread From: Hans de Goede @ 2023-01-23 13:28 UTC (permalink / raw) To: Mark Gross Cc: Hans de Goede, Andy Shevchenko, platform-driver-x86, kernel test robot Fix the following . 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 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.. should we also have a diagnostic for the (presumed) user error? 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). 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. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? static_cast on the other hand should deny your stripping away the const qualifier. Making statements based on opinion; back them up with references or personal experience. In such a case the programmer can use a void pointer to point to the location of the unknown data type. How Intuit democratizes AI development across teams through reusability. that any valid pointer to void can be converted to this type, then 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. Note the difference between the type casting of a variable and type casting of a pointer. I'm using cocos2d-x-2.2.2. You use the address-of operator & to do that. Implementing From will result in the Into implementation but not vice-versa. This solution is in accordance with INT18-C. */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j;
So you know you can cast it back like this. unsigned long call_fn = (unsigned long)FUNC; Infact I know several systems where that does not hold. What is the correct method to cast an int to a void*? Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. 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. You can only do this if you use a synchronization primitive to ensure that there is no race condition. How to notate a grace note at the start of a bar with lilypond? A cast converts an object or value from one type to another. SQL Server does not automatically promote . The problem just occur with Xcode 5.1. What happens if you typecast as unsigned first? [that could be a TODO - not to delay solving the ICE]. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); What is the point of Thrower's Bandolier? If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. The int data type is the primary integer data type in SQL Server. reinterpret_cast is a type of casting operator used in C++. Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. Error while setting app icon and launch image in xcode 5.1. 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). Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. rev2023.3.3.43278. 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. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Remarks. In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. 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. 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. } SCAN_END_SINGLE(ATTR) And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. @Martin York: No, it doesn't depend on endiannness. @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? Whats the grammar of "For those whose stories they are"? If the value is ever used as pointer again that will prove to be an extremely bad idea. property that any valid pointer to void can be converted to this type, C/C++ , Cerror: cast to 'void *' from smaller integer type 'int'. 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. Your first example is risky because you have to be very careful about the object lifetimes. What does casting to void* does when passing arguments to variadic functions? And when assigning to a void pointer, all type information is lost. 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;. what happens when we typecast normal variable to void* or any pointer variable? But the problem has still happened. In C (int)b is called an explicit conversion, i.e. 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)). Find centralized, trusted content and collaborate around the technologies you use most. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. STR34-C. Visit Microsoft Q&A to post new questions. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. There are ways to prevent this: pass a dynamic allocated argument if your not the passing thread is not static or if your argument is a local variable, otherwise there is no issue. whether it was an actual problem is a different matter though. Connect and share knowledge within a single location that is structured and easy to search. Replacing broken pins/legs on a DIP IC package, AC Op-amp integrator with DC Gain Control in LTspice. Does Counterspell prevent from any further spells being cast on a given turn? 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. 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. Safe downcast may be done with dynamic_cast. This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. You should perform type conversion based on 64bit build system because the type "int" supports only -32768 ~ 32768. "After the incident", I started to be more careful not to trip over things. Why do academics stay as adjuncts for years rather than move around? If int is no larger than pointer to void then one way to store the value is by simply copying the bytes: int i . Type casting is when you assign a value of one primitive data type to another type. This page was last modified on 12 February 2023, at 18:25. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. A nit: in your version, the cast to void * is unnecessary. 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; SCAN_PUT(ATTR, NULL); you can just change architecture to support 32 bit compilation by all below in in Build Settings. 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. Issues. 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
The following program casts a double to an int. *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 . Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" You are right! Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? 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. ^~~~~~~~~~~~~~~~~~~~~ ), Styling contours by colour and by line thickness in QGIS. 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;. Connect and share knowledge within a single location that is structured and easy to search. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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; From that point on, you are dealing with 32 bits. You can use any other pointer, or you can use (size_t), which is 64 bits. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. However even though their types are different, the address is going to be the same. 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. No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. If you preorder a special airline meal (e.g. 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 [.]) Or, they are all wrong. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Fork 63. equal to the original pointer: First you are using a define, which is not a variable. There is no "correct" way to store a 64-bit pointer in an 32-bit integer. Using Kolmogorov complexity to measure difficulty of problems? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Can Martian regolith be easily melted with microwaves? Functions return bigint only if the parameter expression is a bigint data type. It generally takes place when in an expression more than one data type is present. 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. 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. Thanks. Pd = Pa; Similarly, Pc may be type cast to type int and assigned the value Pa. 1. @DavidHeffernan I rephrased that sentence a little. I am compiling this program in linux gcc compiler.. If you cast an int pointer int, you might get back a different integer. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini An open (void) pointer can hold a pointer of any type. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. Asking for help, clarification, or responding to other answers. Is it possible to create a concave light? This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. If the destination type is bool, this is a boolean conversion (see below). Identify those arcade games from a 1983 Brazilian music video. Asking for help, clarification, or responding to other answers. Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. how to cascade 2d int array to 2d void pointer array? 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. warning C4311: 'type cast': pointer truncation from 'void *' to 'long' in ECPG test files. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Click to see the query in the CodeQL repository. (int) pthread_self() 64int48intuintptr_t (unsigned int) Asking for help, clarification, or responding to other answers. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical.
Woman Found Dead In The Bronx,
Forever In Our Hearts Until We Meet Again,
Articles C