cast to void *' from smaller integer type 'int

Safe downcast may be done with dynamic_cast. this question. You can fix this error by replacing this line of code. This is not a conversion at all. Casting arguments inside the function is a lot safer. Don't do that. While working with Threads in C, I'm facing the warning, "warning: cast to pointer from integer of different size". You need to pass an actual pointer. Making statements based on opinion; back them up with references or personal experience. *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 . I need to cast the int from the first function so that I can use it as an argument for the second function. This allows you to reinterpret the void * as an int. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. linux c-pthreads: problem with local variables. 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; Usually that means the pointer is allocated with. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. Now, what happens when I run it with the thread sanitizer? How Intuit democratizes AI development across teams through reusability. However even though their types are different, the address is going to be the same. (Also, check out how it prints "5" twice), passing a unique pointer to each thread wont race, and you can get/save any kind of information in the th struct. Referring to N1570 7.20.1.4/p1 (Integer types capable of holding object pointers): The following type designates a signed integer type with the property No idea how it amassed 27 upvotes?! By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. // 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. There's no proper way to cast this to int in general case. What I am saying is that it would be safer to use new(5) rather than 5 and deal with it appropriately at the other end. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Disconnect between goals and daily tasksIs it me, or the industry? C++ how to get the address stored in a void pointer? 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. The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. 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. 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. And in this context, it is very very very common to see programmers lazily type cast the. Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. This is known as implicit type casting or type promotion, compiler automatically converts smaller data type to larger data type. 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; Click to see the query in the CodeQL repository. I'm trying to learn pthreads and thing that keeps bugging me is how do i really pass argument to the function. The difference between the phonemes /p/ and /b/ in Japanese. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. I think the solution 3> should be the correct one. (int) pthread_self() 64int48intuintptr_t (unsigned int) So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. @Shahbaz you could but I will not suggest to a C newbie to use globals. Thanks for contributing an answer to Stack Overflow! 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. This is a fine way to pass integers to new pthreads, if that is what you need. then converted back to pointer to void, and the result will compare The reinterpret_cast makes the int the size of a pointer and the warning will stop. 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. Keep in mind that thrArg should exist till the myFcn() uses it. Connect and share knowledge within a single location that is structured and easy to search. 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). So,solution #3 works 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. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? What video game is Charlie playing in Poker Face S01E07? Remarks. There's no proper way to cast this to int in general case. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. Making statements based on opinion; back them up with references or personal experience. You can use any other pointer, or you can use (size_t), which is 64 bits. 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). To cast such pointers to 32-bit types and vice versa special functions are used: void * Handle64ToHandle ( const void * POINTER_64 h ) void * POINTER_64 HandleToHandle64 ( const void *h ) long HandleToLong ( const void *h ) unsigned long HandleToUlong ( const void *h ) That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. Acidity of alcohols and basicity of amines. 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;. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. @DavidHeffernan I rephrased that sentence a little. In the case of Widening Type Casting, the lower data type (having smaller size) is converted into the higher data type (having larger size). rev2023.3.3.43278. C/C++ , Cerror: cast to 'void *' from smaller integer type 'int'. 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. Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. Use returnPtr[j] = (void *) ((long)ptr + i); ). ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' Infact I know several systems where that does not hold. Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. 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. A nit: in your version, the cast to void * is unnecessary. vegan) just to try it, does this inconvenience the caterers and staff? I wish that you write those answer first than the explanation. SCAN_PUT(ATTR, NULL); On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. 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. Windows has 32 bit long only on 64 bit as well. 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. 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. The problem was there before, you just are being notified of it. In C (int)b is called an explicit conversion, i.e. This is flat out wrong. Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. Converting one datatype into another is known as type casting or, type-conversion. Where does this (supposedly) Gibson quote come from? Your first example is risky because you have to be very careful about the object lifetimes. Implementation-dependent. Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. 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. Why does setupterm terminate the program? Based on the design of this function, which modification is right. The value of float variable is= 37.75. ), Styling contours by colour and by line thickness in QGIS. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. 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. How to convert a factor to integer\numeric without loss of information? FAILED: lib/libopenvswitch.a.p/odp-util.c.obj What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Note:You might receive a runtime exception if the pointer contains a value unsuitable for the context. In this case, casting the pointer back to an integer is meaningless, because . This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Converts between types using a combination of implicit and user-defined conversions. I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. Returns a value of type new-type. I'm using cocos2d-x-2.2.2. How do I align things in the following tabular environment? The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); The difference between a and &a is the type. 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. for saving RAM), use union, and make sure, if the mem address is treated as an int only if you know it was last set as an int. The correct answer is, if one does not mind losing data precision. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. 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. Type casting is when you assign a value of one primitive data type to another type. Yeah, the tutorial is doing it wrong. This is an old C callback mechanism so you can't change that. "After the incident", I started to be more careful not to trip over things. 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. 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. You can only do this if you use a synchronization primitive to ensure that there is no race condition. converted back to pointer to void, and the result will compare equal Sign in ^~~~~~~~~~~~~~~~~~~~~ The following program casts a double to an int. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^~~~~~~~~~~~~~~~~~~~~ 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. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini 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. 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. Don't pass your int as a void*, pass a int* to your int, so you can cast the void* to an int* and copy the dereferenced pointer to your int. This is what the second warning is telling you. In the first example, the variable c1 of the char type is converted to a temporary variable of the int type, because the second operand in the division operation, the constant 2, is of the higher type int. How to correctly cast a pointer to int in a 64-bit application?

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