I would create a structure and pass that as void* to pthread_create. I need to cast the int from the first function so that I can use it as an argument for the second function. Now, what happens when I run it with the thread sanitizer? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Where does this (supposedly) Gibson quote come from? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? What you do here is undefined behavior, and undefined behavior of very practical sort. 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. 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. reinterpret_cast<void *>(42)). What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? It generally takes place when in an expression more than one data type is present. You may declare a const int variable and cast its reference to the void*. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. In such a case the programmer can use a void pointer to point to the location of the unknown data type. Thanks for contributing an answer to Stack Overflow! The most general answer is - in no way. You can use any other pointer, or you can use (size_t), which is 64 bits. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. Can Martian regolith be easily melted with microwaves? It modifies >> Wconversion-real.c, Wconversion-real-integer.c and pr35635.c to be more >> specific > > If the patch passes existing tests, I'd be inclined to leave them > tests alone and add new ones that are specific to what this patch > changes. But then you need to cast your arguments inside your thread function which is quite unsafe cf. 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. 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). Mutually exclusive execution using std::atomic? SCAN_PUT_ATTR(mask, ATTR, smask, FUNC); For example, the main thread could wait for all of the other threads to end before terminating. This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). How to use Slater Type Orbitals as a basis functions in matrix method correctly? How to get the error message from the error code returned by GetLastError()? Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. what does it mean to convert int to void* or vice versa? even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. Floating-point conversions I am an entry level C programmer. You are getting warnings due to casting a void* to a type of a different size. Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. It solved my problem too. You can convert the values from one type to another explicitly using the cast operator as follows (type_name) expression Are there tables of wastage rates for different fruit and veg? Just edited. Thanks for contributing an answer to Stack Overflow! My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? A missing cast in the new fast > enumeration code. Getting Command /bin/sh failed with exit code 65 Error with Xcode 5.1 . AC Op-amp integrator with DC Gain Control in LTspice. 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. A sane compiler may throw a warning on lines like this but by no way it should throw an error, because this code is NOT wrong, it is just potentially error-prone, but can be perfectly valid. (void *)i Error: cast to 'void *' from smaller integer type 'int'. In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. ^~~~~~~~~~~~~~~~~~~~ "clang" "-Ilib\libopenvswitch.a.p" "-Ilib" "-I..\lib" "-I." Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. And then assign it to the double variable. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Why do academics stay as adjuncts for years rather than move around? However the actual code in question contains an explicit c-style cast to int. 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. : iPhone Retina 4-inch 64-bit) is selected. The following program casts a double to an int. How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? You are getting warnings due to casting a void* to a type of a different size. To learn more, see our tips on writing great answers. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? Use #include to define it. If your standard library (even if it is not C99) happens to provide these types - use them. 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). Windows has 32 bit long only on 64 bit as well. Using Kolmogorov complexity to measure difficulty of problems? It is commonly called a pointer to T and its type is T*. But I don't want to edit code in "EAGLView.mm" because it's a "library file". pthread passes the argument as a void*. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Setting a buffer of char* with intermediate casting to int*. 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. equal to the original pointer: First you are using a define, which is not a variable. rev2023.3.3.43278. 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. I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. Please help me compile Chez Scheme. 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. In the case of Widening Type Casting, the lower data type (having smaller size) is converted into the higher data type (having larger size). ^~~~~~~~~~~~~~~~~~~~~ What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. itch" "-I..\include\windows" "-Iinclude" "-I..\include" "-I..\datapath-windows\include" "-IC:\PTHREADS-BUILT\include" "-Xclang" "-fcolor-diagnostics" "-pipe" C99 defines the types "intptr_t" and "uintptr_t" which do . To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The difference between the phonemes /p/ and /b/ in Japanese. Find centralized, trusted content and collaborate around the technologies you use most. In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). 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 byte -> short -> char -> int -> long -> float -> double. 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. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? The problem just occur with Xcode 5.1. Identify those arcade games from a 1983 Brazilian music video. and how to print the thread id of 2d array argument? This page has been accessed 1,655,678 times. Recovering from a blunder I made while emailing a professor. Usually that means the pointer is allocated with. Just want to point out that the purpose of threads is, +1 absolutely true, but if you take you time to write struct {}, you can save a lot of troubles in the future when you want to receive/send more data then just an int. But gcc always give me a warning, that i cannot cast an int to a void*. From the question I presume the OP does. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : rev2023.3.3.43278. What video game is Charlie playing in Poker Face S01E07? You should perform type conversion based on 64bit build system because the type "int" supports only -32768 ~ 32768. You can fix this error by replacing this line of code. By clicking Sign up for GitHub, you agree to our terms of service and this way you won't get any warning. But assuming that it is, as long as the caller and the callee agree, you can do that sort of thing. . error: cast from pointer to smaller type 'unsigned int' loses information. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? (i.e. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Basically its a better version of (void *)i. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. The high-order 9 bits of the number are used to hold a flag value, and the result is converted back into a pointer. Why do small African island nations perform better than African continental nations, considering democracy and human development? Bulk update symbol size units from mm to map units in rule-based symbology. 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 linux c-pthreads: problem with local variables. privacy statement. On all of them int is 32bit, not 16bit. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. What is the point of Thrower's Bandolier? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. You use the address-of operator & to do that. The following behavior-changing defect reports were applied retroactively to previously published C++ standards. But I'm nitpicking .. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini If any, how can the original function works without errors if we just ignore the warning. Don't do that. This forum has migrated to Microsoft Q&A. Why did Ukraine abstain from the UNHRC vote on China? /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. Making statements based on opinion; back them up with references or personal experience. And when assigning to a void pointer, all type information is lost. Safe downcast may be done with dynamic_cast. Infact I know several systems where that does not hold. 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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 ) ../lib/odp-util.c:5489:33: note: expanded from macro 'SCAN_PUT_ATTR' Not the answer you're looking for? 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). Before I update Xcode, my project still can build and run normally with all devices. 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). SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); you can just change architecture to support 32 bit compilation by all below in in Build Settings. Projects. 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. 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. Using printf with a pointer to float gives an error, Meaning of int (*) (int *) = 5 (or any integer value), Casting int to void* loses precision, and what is the solution in required cases, Acidity of alcohols and basicity of amines. (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. Can anybody explain how to pass an integer to a function which receives (void * ) as a parameter? Pull requests. As for the stack, I've written a few libraries using pthreds, thus I don't agree that what you describe "is quite often the case". to the original pointer: The following type designates an unsigned integer type with the [that could be a TODO - not to delay solving the ICE]. 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. You are right! 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. Acidity of alcohols and basicity of amines. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Visit Microsoft Q&A to post new questions. You are just making it bigger by tricking the compiler and the ABI. This is an old C callback mechanism so you can't change that. This is known as implicit type casting or type promotion, compiler automatically converts smaller data type to larger data type. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The text was updated successfully, but these errors were encountered: Connect and share knowledge within a single location that is structured and easy to search. @Shahbaz you could but I will not suggest to a C newbie to use globals. You are correct, but cocos actually only uses that address as a unique id. reinterpret_cast is a type of casting operator used in C++. What is the difference between const int*, const int * const, and int const *? 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. warning C4311: 'type cast': pointer truncation from 'void *' to 'long' in ECPG test files. Find centralized, trusted content and collaborate around the technologies you use most. 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. 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 use $(ARCHS_STANDARD_32_BIT) at Architecture instead of $(ARCHS_STANDARD). Click to see the query in the CodeQL repository. 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. [] 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). And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. My code is all over the place now but I appreciate you all helping me on my journey to mastery! Asking for help, clarification, or responding to other answers. @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. Using Kolmogorov complexity to measure difficulty of problems? this way I convert an int to a void* which is much better than converting a void* to an int. 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 flat out wrong. I get the error: "cast to smaller integer type 'int' from 'string' (aka 'char *')" referencing line of code: while (isalpha(residents[i].name) == 0), How Intuit democratizes AI development across teams through reusability. For the Nozomi from Shinagawa to Osaka, say on a Saturday afternoon, would tickets/seats typically be available - or would you need to book? The value of float variable is= 37.75. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. How do I count the number of sentences in C using ". Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? C / C++ Forums on Bytes. Is it possible to create a concave light? If the original pointer value represents an address of a byte in memory that does not satisfy the alignment requirement of the target type, then the resulting pointer value is unspecified. If the function had the correct signature you would not need to cast it explicitly. */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; The OP wanted to convert a pointer value to a int value, instead, most the answers, one way or the other, tried to wrongly convert the content of arg points to to a int value. You use the address-of operator & to do that int x = 10; void *pointer = &x; And in the function you get the value of the pointer by using the dereference operator *: int y = * ( (int *) pointer); Share Improve this answer Follow edited Apr 15, 2013 at 13:58 answered Apr 15, 2013 at 13:53 Some programmer dude 394k 35 393 602 1 Connect and share knowledge within a single location that is structured and easy to search. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. 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; A nit: in your version, the cast to void * is unnecessary. 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 incident has nothing to do with me; can I use this this way? In such condition type conversion (type promotion) takes place to avoid loss of data. 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. ^~~~~~~~~~~~~~~~~~~ By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); lexborisov Modest Public. Hence there is no loss in data. For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). ^~~~~~~~~~~~~~~~~~~~~ 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;. Is a PhD visitor considered as a visiting scholar. To avoid truncating your pointer, cast it to a type of identical size. to your account, [87/252] Compiling C object lib/libopenvswitch.a.p/odp-util.c.obj The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. There is absolutely not gurantee that sizeof(int) <= sizeof(void*). Why does flowing off the end of a non-void function without returning a value not produce a compiler error? The problem was there before, you just are being notified of it. However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. If the value is ever used as pointer again that will prove to be an extremely bad idea. I have a two functions, one that returns an int, and one that takes a const void* as an argument. No idea how it amassed 27 upvotes?! error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. pthread create managing values generated in function (in c), Establishing TCP socket connection between PHP client and C server on Ubuntu. 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. SCAN_PUT(ATTR, NULL); this question. You think by casting it here that you are avoiding the problem! ", "? ), Styling contours by colour and by line thickness in QGIS. whether it was an actual problem is a different matter though. 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". In this case, casting the pointer back to an integer is meaningless, because . 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. This is what the second warning is telling you. Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. 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). return ((void **) returnPtr);} /* Matrix() */. Example: int x=7, y=5; float z; z=x/y; /*Here the value of z is 1*/. 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 All character types are to be converted to an integer. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. How to convert a factor to integer\numeric without loss of information? Mutually exclusive execution using std::atomic? Here is my code: I already tried (void*)M_TABLE_SIZE but then I get an error that I cannot use the * operator. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. GitHub. The only alternative is really to take time and fix all 64-bit code issues, of which there may be some non-trivial issues. Anw, the project still build and run normally when i use Xcode 5.0 with iOS 7.0. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. Note the difference between the type casting of a variable and type casting of a pointer. 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. Why is this sentence from The Great Gatsby grammatical? An open (void) pointer can hold a pointer of any type. A nit: in your version, the cast to void * is unnecessary. You could use this code, and it would do the same thing as casting ptr to (char*). Why is there a voltage on my HDMI and coaxial cables? 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" (. I assumed that gcc makes a 65536 out of my define, but I was wrong. // 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.

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