cast to void *' from smaller integer type 'int

Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. // 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. Bulk update symbol size units from mm to map units in rule-based symbology. long guarantees a pointer size on Linux on any machine. 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. ), Styling contours by colour and by line thickness in QGIS. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Use returnPtr[j] = (void *) ((long)ptr + i); ). Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. But gcc always give me a warning, that i cannot cast an int to a void*. 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). Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. 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 the value is ever used as pointer again that will prove to be an extremely bad idea. Click to see the query in the CodeQL repository. If the original type is a void *, converting to an int may lose date on platforms where sizeof(void *) != sizeof(int) (which is true of LP64 programming model). 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. @BlueMoon Thanks a lot! error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. I think the solution 3> should be the correct one. You may declare a const int variable and cast its reference to the void*. Find centralized, trusted content and collaborate around the technologies you use most. This is an old C callback mechanism so you can't change that. No idea how it amassed 27 upvotes?! LLNL's tutorial is bad and they should feel bad. Implementation-dependent. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. 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. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. byte -> short -> char -> int -> long -> float -> double. 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. 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. Pull requests. You just need to suppress the warning, and this will do it: This may offend your sensibilities, but it's very short and has no race conditions (as you'd have if you used &i). To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. Can I tell police to wait and call a lawyer when served with a search warrant? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. What is the difference between const int*, const int * const, and int const *? Casting arguments inside the function is a lot safer. @DietrichEpp can you explain what is race condition with using. Identify those arcade games from a 1983 Brazilian music video. The difference between a and &a is the type. Connect and share knowledge within a single location that is structured and easy to search. 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. Implicit Type Conversion is also known as 'automatic type conversion'. In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. Using an integer address (like &x) is probably wrong, indeed each modification you will execute on x will affect the pass behaviour. Note that it's not guaranteed that casting an, Generally this kind of type casting does not lead to any concern as long as the addresses are encoded using the same length as the "variable type" (. converted back to pointer to void, and the result will compare equal The only alternative is really to take time and fix all 64-bit code issues, of which there may be some non-trivial issues. As a result of the integer division 3/2 we get the value 1, which is of the int type. That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. 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. You think by casting it here that you are avoiding the problem! Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Dinesh: could you please 1) show us those. ^~~~~~~~~~~~~~~~~~~~~ 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 function had the correct signature you would not need to cast it explicitly. 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. Making statements based on opinion; back them up with references or personal experience. Terrible solution. */ >> -bool >> +enum conversion_safety >> unsafe_conversion_p (tree type, tree expr, bool . In such a case the programmer can use a void pointer to point to the location of the unknown data type. To be honest, I think, clang is too restrictive here. - the incident has nothing to do with me; can I use this this way? This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ you can just change architecture to support 32 bit compilation by all below in in Build Settings. So,solution #3 works just fine. 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). 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. If you cast an int pointer int, you might get back a different integer. Have a question about this project? 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 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;. Where does this (supposedly) Gibson quote come from? 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. Asking for help, clarification, or responding to other answers. In C (int)b is called an explicit conversion, i.e. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. rev2023.3.3.43278. If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. C++ how to get the address stored in a void pointer? 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; -1, Uggh. A cast converts an object or value from one type to another. 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. You can fix this error by replacing this line of code. Asking for help, clarification, or responding to other answers. I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . 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). 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. Is a PhD visitor considered as a visiting scholar. "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. So you know you can cast it back like this. 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. Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. It is commonly called a pointer to T and its type is T*. Using indicator constraint with two variables. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini In my case, I was using a 32-bit value that needed to be passed to an OpenGL function as a void * representing an offset into a buffer. 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". rev2023.3.3.43278. @DavidHeffernan I rephrased that sentence a little. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' [that could be a TODO - not to delay solving the ICE]. GitHub. 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 [] 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). In such condition type conversion (type promotion) takes place to avoid loss of data. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); What is the correct method to cast an int to a void*? Thanks for contributing an answer to Stack Overflow! 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. How to get the error message from the error code returned by GetLastError()? This page was last modified on 12 February 2023, at 18:25. A missing cast in the new fast > enumeration code. x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. *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 . This forum has migrated to Microsoft Q&A. Don't do that. The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to.