All float types are to be converted to double. 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. Thanks for contributing an answer to Stack Overflow! Why do academics stay as adjuncts for years rather than move around? 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. Did i have to face to unexpected runtime issues, i guess not, i've found another discussion on this -. The preprocessor will replace your code by this: This is unlikely what you are trying to do. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. What does casting to void* does when passing arguments to variadic functions? On all of them int is 32bit, not 16bit. How Intuit democratizes AI development across teams through reusability. And in the function you get the value of the pointer by using the dereference operator *: Please read why glib provide macros for this kind of conversions, there's no need to repeat the text here. We have to pass address of the variable to the function because in function definition argument is pointer variable. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? Is a PhD visitor considered as a visiting scholar. The text was updated successfully, but these errors were encountered: It solved my problem too. And, most of these will not even work on gcc4. Now, what happens when I run it with the thread sanitizer? Why does Mister Mxyzptlk need to have a weakness in the comics? 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. Basically its a better version of (void *)i. -1, Uggh. Connect and share knowledge within a single location that is structured and easy to search. @BlueMoon Thanks a lot! The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. 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. How to correctly cast a pointer to int in a 64-bit application? 471,961 Members | 900 Online. ^~~~~~~~~~~~~~~~~~~~~ reinterpret_cast<void *>(42)). Why is there a voltage on my HDMI and coaxial cables? casting from int to void* and back to int. ", "!"? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Your first example is risky because you have to be very careful about the object lifetimes. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). ncdu: What's going on with this second size column? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. I have a two functions, one that returns an int, and one that takes a const void* as an argument. 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. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" I wish that you write those answer first than the explanation. It's always a good practice to put your #define's in brackets to avoid such surprise. Whats the grammar of "For those whose stories they are"? Converting a pointer to an integer whose result cannot represented in the integer type is undefined behavior is C and prohibited in C++. return ((void **) returnPtr);} /* Matrix() */. Can I tell police to wait and call a lawyer when served with a search warrant? If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. 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. Mutually exclusive execution using std::atomic? But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. C++ how to get the address stored in a void pointer? Floating-point conversions What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Asking for help, clarification, or responding to other answers. 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. When is casting void pointer needed in C? Why does setupterm terminate the program? ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' this way I convert an int to a void* which is much better than converting a void* to an int. Since gcc compiles that you are performing arithmetic between void* and an int (1024). long guarantees a pointer size on Linux on any machine. B programing language is a language based on basic combined programming or a BCPL, and it is the precursor of the C programming language. 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;. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. Yeah, the tutorial is doing it wrong. Well occasionally send you account related emails. Have a question about this project? You use the address-of operator & to do that. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. How to get the error message from the error code returned by GetLastError()? To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. Is it possible to create a concave light? Asking for help, clarification, or responding to other answers. How do I align things in the following tabular environment? reinterpret_cast is a type of casting operator used in C++. ^~~~~~~~~~~~~~~~~~~ The problem is not with casting, but with the target type loosing half of the pointer. This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. Thanks for contributing an answer to Stack Overflow! /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. But assuming that it is, as long as the caller and the callee agree, you can do that sort of thing. How to use Slater Type Orbitals as a basis functions in matrix method correctly? Implementation-dependent. Why is this sentence from The Great Gatsby grammatical? "After the incident", I started to be more careful not to trip over things. Replacing broken pins/legs on a DIP IC package, How to handle a hobby that makes income in US. 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. Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. A void pointer can be really useful if the programmer is not sure about the data type of data inputted by the end user. The following program casts a double to an int. 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). Keep in mind that thrArg should exist till the myFcn() uses it. For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. Asking for help, clarification, or responding to other answers. ncdu: What's going on with this second size column? 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. (void *)i Error: cast to 'void *' from smaller integer type 'int'. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? 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. What I am trying to emphasis that conversion from int to pointer and back again can be frough with problems as you move from platform to platform. I don't see how anything bad can happen . Converts between types using a combination of implicit and user-defined conversions. Thanks for contributing an answer to Stack Overflow! Use returnPtr[j] = (void *) ((long)ptr + i); ). Why did Ukraine abstain from the UNHRC vote on China? 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. Difficulties with estimation of epsilon-delta limit proof. What is the purpose of non-series Shimano components? Disconnect between goals and daily tasksIs it me, or the industry? vegan) just to try it, does this inconvenience the caterers and staff? From that point on, you are dealing with 32 bits. However the actual code in question contains an explicit c-style cast to int. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. 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 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. Put your define inside a bracket: without a problem. Api says this is how i should create thread: So if I want to pass an int what I think I should do is: The second example assumes that a pointer is wide enough to store an int. This is not even remotely "the correct answer". You are right! Is it possible to create a concave light? 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. 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. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ vegan) just to try it, does this inconvenience the caterers and staff? How to use Slater Type Orbitals as a basis functions in matrix method correctly? Linear regulator thermal information missing in datasheet. To learn more, see our tips on writing great answers. The most general answer is - in no way. */ >> -bool >> +enum conversion_safety >> unsafe_conversion_p (tree type, tree expr, bool . 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. "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini LLNL's tutorial is bad and they should feel bad. Does a summoned creature play immediately after being summoned by a ready action? 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. 1. The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. RNINGS" "-D_CRT_SECURE_NO_DEPRECATE" -MD -MQ lib/libopenvswitch.a.p/odp-util.c.obj -MF "lib\libopenvswitch.a.p\odp-util.c.obj.d" -o lib/libopenvswitch.a.p/od Why does flowing off the end of a non-void function without returning a value not produce a compiler error? 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. You can fix this error by replacing this line of code. I usually have all automatic conversion warnings effective when developing in C, and I use explicit casting in order to suppress a specific . What is the purpose of non-series Shimano components? I think the solution 3> should be the correct one. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? This is not a conversion at all. Thank you all for your feedback. 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 page has been accessed 1,655,678 times. Disconnect between goals and daily tasksIs it me, or the industry? B language was designed to develop . 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. 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). To subscribe to this RSS feed, copy and paste this URL into your RSS reader. So reinterpret_cast has casted it to long type and then static_cast safely casts long to int, if you are ready do truncte the data. If the value is ever used as pointer again that will prove to be an extremely bad idea. 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. If you convert (void*) to (long) no precision is lost, then by assigning the (long) to an (int), it properly truncates the number to fit. tialized" "-Wno-format" "-Wno-incompatible-pointer-types" "-Werror" "-dM" "-U_MSC_VER" "-D_TIMESPEC_DEFINED" "-D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_SECURE_NO_WA 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 (int) pthread_self() 64int48intuintptr_t (unsigned int) Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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; 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. To learn more, see our tips on writing great answers. There's no proper way to cast this to int in general case. 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. If you are going to pass the address you typically need to exert some more control over the lifetime of the object. No idea how it amassed 27 upvotes?! Converting one datatype into another is known as type casting or, type-conversion. The text was updated successfully, but these errors were encountered: You signed in with another tab or window. 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. The dynamic_cast<>operator provides a way to check the actual type of a pointer to a polymorphic class. How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. 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. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. @DavidHeffernan I rephrased that sentence a little. Mutually exclusive execution using std::atomic? 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. Connect and share knowledge within a single location that is structured and easy to search. In such a case the programmer can use a void pointer to point to the location of the unknown data type. 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 A nit: in your version, the cast to void * is unnecessary. [] 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). ../lib/odp-util.c:5489:33: note: expanded from macro 'SCAN_PUT_ATTR' Identify those arcade games from a 1983 Brazilian music video. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. A missing cast in the new fast > enumeration code. Don't do that. /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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". void* -> integer -> void* rather than integer -> void* -> integer. This page was last modified on 12 February 2023, at 18:25. Where does this (supposedly) Gibson quote come from? and how to print the thread id of 2d array argument? It is purely a compile-time directive which instructs the compiler to treat expression as if it had . ), For those who are interested. 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). As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] I am an entry level C programmer. windows meson: cast to smaller integer type 'unsigned long' from 'void *'. If you preorder a special airline meal (e.g. (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. Pull requests. The subreddit for the C programming language, Press J to jump to the feed. Projects. ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. Thanks. Recovering from a blunder I made while emailing a professor. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. Returns a value of type new-type. Star 675. 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. How can this new ban on drag possibly be considered constitutional? You think by casting it here that you are avoiding the problem! Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. Replacing broken pins/legs on a DIP IC package, AC Op-amp integrator with DC Gain Control in LTspice. should we also have a diagnostic for the (presumed) user error? Using Kolmogorov complexity to measure difficulty of problems? @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. Please help me compile Chez Scheme. Press question mark to learn the rest of the keyboard shortcuts. Functions return bigint only if the parameter expression is a bigint data type. Can I tell police to wait and call a lawyer when served with a search warrant? returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size); Find centralized, trusted content and collaborate around the technologies you use most. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Remembering to delete the pointer after use so that we don't leak. Before I update Xcode, my project still can build and run normally with all devices. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy.

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