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. Issues. Types - D Programming Language Are there tables of wastage rates for different fruit and veg? ^~~~~~~~~~~~~~~~~~~~ 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.. 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. And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. Here is my code: I already tried (void*)M_TABLE_SIZE but then I get an error that I cannot use the * operator. *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 . } SCAN_END_SINGLE(ATTR) Re: [PATCH, PR 53001] Re: Patch to split out new warning flag for B Programming Language | What is the History and Concept? 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 [.]) Making statements based on opinion; back them up with references or personal experience. p-util.c.obj "-c" ../lib/odp-util.c For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. In such condition type conversion (type promotion) takes place to avoid loss of data. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. what does it mean to convert int to void* or vice versa? @DietrichEpp can you explain what is race condition with using. Using indicator constraint with two variables. The problem is not with casting, but with the target type loosing half of the pointer. The subreddit for the C programming language, Press J to jump to the feed. @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. Press question mark to learn the rest of the keyboard shortcuts. A nit: in your version, the cast to void * is unnecessary. This is an old C callback mechanism so you can't change that. @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. 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. 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. Why does setupterm terminate the program? Why is there a voltage on my HDMI and coaxial cables? 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. Thanks for contributing an answer to Stack Overflow! Cast Operations - Oracle *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 . That could create all kinds of trouble. There's no proper way to cast this to int in general case. Java Type Casting - W3Schools Casting type void to uint8_t - Arduino Forum Number Type Cast | Qt Forum 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. Mutually exclusive execution using std::atomic? What does casting to void* does when passing arguments to variadic functions? When is casting void pointer needed in C? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. sound/soc/codecs/tlv320aic32x4.c:1202:18: warning: cast to smaller 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. You may declare a const int variable and cast its reference to the void*. What is the difference between const int*, const int * const, and int const *? B language was designed to develop . 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. This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. I wish that you write those answer first than the explanation. Does Counterspell prevent from any further spells being cast on a given turn? What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? and how to print the thread id of 2d array argument? LLNL's tutorial is bad and they should feel bad. 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. Can Martian regolith be easily melted with microwaves? STR34-C. This page was last modified on 12 February 2023, at 18:25. You could use this code, and it would do the same thing as casting ptr to (char*). So you know you can cast it back like this. In the case of Widening Type Casting, the lower data type (having smaller size) is converted into the higher data type (having larger size). x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. Why does flowing off the end of a non-void function without returning a value not produce a compiler error? iphone - Error "Cast from pointer to smaller type 'int' loses How do I check if a string represents a number (float or int)? Your first example is risky because you have to be very careful about the object lifetimes. Can I tell police to wait and call a lawyer when served with a search warrant? 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. 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. clang11 report error: cast to smaller integer type #82 - GitHub Why is this sentence from The Great Gatsby grammatical? Usually that means the pointer is allocated with. windows meson: cast to smaller integer type 'unsigned long' from 'void *'. Remarks. I have a two functions, one that returns an int, and one that takes a const void* as an argument. It solved my problem too. 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. There's no proper way to cast this to int in general case. You use the address-of operator & to do that. You can only do this if you use a synchronization primitive to ensure that there is no race condition. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' It is commonly called a pointer to T and its type is T*. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Any help with this is appreciated. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. SCAN_PUT_ATTR(key, ATTR, skey, FUNC); Find centralized, trusted content and collaborate around the technologies you use most. 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 returns the first 32 bits of the pointer which may be the top or the bottom depending on big versus little endian, as comment #2 said. Only the following conversions can be done with static_cast, except when such conversions would cast away constness or volatility. Typically, long or unsigned long is . 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. FAILED: lib/libopenvswitch.a.p/odp-util.c.obj 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" (. As a result of the integer division 3/2 we get the value 1, which is of the int type. Fork 63. An open (void) pointer can hold a pointer of any type. If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. Taking the above declarations of A, D, ch of the . It is easier to understand and write than any other assembly language. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Functions return bigint only if the parameter expression is a bigint data type. 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. Since the 'size' argument for your function is the number of bytes each element in the array needs, I think casting the pointerto (char*) is appropriate. 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. [] 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). Find centralized, trusted content and collaborate around the technologies you use most. What is the purpose of non-series Shimano components? 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. Remembering to delete the pointer after use so that we don't leak. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Is a PhD visitor considered as a visiting scholar. But the problem has still happened. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. 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. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] Casting type int to const void* - C / C++ 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 On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. "I think what you should do is actually pass the address of the variable to the function" Not necessarily. The following behavior-changing defect reports were applied retroactively to previously published C++ standards. Converting a void* to an int is non-portable way that may work or may not! ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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. I think the solution 3> should be the correct one. And in this context, it is very very very common to see programmers lazily type cast the. ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' 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. Thanks for contributing an answer to Stack Overflow! By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. But gcc always give me a warning, that i cannot cast an int to a void*. 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". Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. All float types are to be converted to double. windows meson: cast to 'HANDLE' (aka 'void *') from smaller integer @Shahbaz you could but I will not suggest to a C newbie to use globals. How to correctly cast a pointer to int in a 64-bit application? That's not a good idea if the original object (that was cast to void*) was an integer. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. 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.
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