No idea how it amassed 27 upvotes?! I am compiling this program in linux gcc compiler.. casting from int to void* and back to int - C / C++ Why does setupterm terminate the program? to the original pointer: The following type designates an unsigned integer type with the Bulk update symbol size units from mm to map units in rule-based symbology. whether it was an actual problem is a different matter though. Returns a value of type new-type. To learn more, see our tips on writing great answers. 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. The problem was there before, you just are being notified of it. ../lib/odp-util.c:5603:13: note: expanded from macro 'SCAN_PUT' ^~~~~~~~~~~~~~~~~~~~ Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, You should be doing int x = *((int *)arg); You are casting from void * to int that is why you get the warning. How create a simple program using threads in C? @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. 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. Floating-point conversions Any help with this is appreciated. ^~~~~~~~~~~~~~~~~~~~ Can Martian regolith be easily melted with microwaves? But the problem has still happened. 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. (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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Thanks. Making statements based on opinion; back them up with references or personal experience. How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. How to tell which packages are held back due to phased updates, Identify those arcade games from a 1983 Brazilian music video. If this is the data to a thread procedure, then you quite commonly want to pass by value. Yeah, the tutorial is doing it wrong. You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Is it possible to create a concave light? I need to cast the int from the first function so that I can use it as an argument for the second function. Using indicator constraint with two variables. To avoid truncating your pointer, cast it to a type of identical size. 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. How do I set, clear, and toggle a single bit? 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. It is easier to understand and write than any other assembly language. rev2023.3.3.43278. How to correctly cast a pointer to int in a 64-bit application? Using Kolmogorov complexity to measure difficulty of problems? I'm using cocos2d-x-2.2.2. Type casting is when you assign a value of one primitive data type to another type. 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". Yeah, the tutorial is doing it wrong. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Getting Command /bin/sh failed with exit code 65 Error with Xcode 5.1 . 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. sound/soc/codecs/tlv320aic32x4.c:1202:18: warning: cast to smaller 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). If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. For example, if you want to store a 'long' value into a simple integer then you can type cast 'long' to 'int'. Please tell me error: cast from 'void*' to 'int' loses precision, How Intuit democratizes AI development across teams through reusability. Implicit conversions - cppreference.com . SQL Server does not automatically promote . Already on GitHub? A cast converts an object or value from one type to another. How to correctly cast a pointer to int in a 64-bit application? Why is there a voltage on my HDMI and coaxial cables? "After the incident", I started to be more careful not to trip over things. 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. ), For those who are interested. In the case of Widening Type Casting, the lower data type (having smaller size) is converted into the higher data type (having larger size). *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 . What is the point of Thrower's Bandolier? Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? 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. To learn more, see our tips on writing great answers. This page has been accessed 1,655,678 times. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Share Improve this answer Follow answered May 6, 2018 at 7:24 Rahul Basically its a better version of (void *)i. Disconnect between goals and daily tasksIs it me, or the industry? ^~~~~~~~~~~~~~~~~~~~~ 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. This solution is in accordance with INT18-C. 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. ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ By clicking Sign up for GitHub, you agree to our terms of service and I cannot reverse my upvote of user384706's answer, but it's wrong. C99 defines the types "intptr_t" and "uintptr_t" which do . Converting one datatype into another is known as type casting or, type-conversion. 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). Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? ../lib/odp-util.c:5658:9: note: expanded from macro 'SCAN_END_SINGLE' ncdu: What's going on with this second size column? Maybe you can try this too. (int*)Pc = pa; After the execution of the above code all the three pointers, i.e., Pa, Pd, and Pc, point to the value 150. 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. How do I align things in the following tabular environment? Or, they are all wrong. To be honest, I think, clang is too restrictive here. 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. to your account, [87/252] Compiling C object lib/libopenvswitch.a.p/odp-util.c.obj What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. This is known as implicit type casting or type promotion, compiler automatically converts smaller data type to larger data type. This allows you to reinterpret the void * as an int. Don't do that. Making statements based on opinion; back them up with references or personal experience. In a 64bit build a pointer is 64bit (contrary to a 32bit build, where it is 32bit), while an int is 32bit, so this assignment stores a 64bit value in a 32bit storage, which may result in a loss of information. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. While working with Threads in C, I'm facing the warning, "warning: cast to pointer from integer of different size". And, most of these will not even work on gcc4. . Does melting sea ices rises global sea level? what does it mean to convert int to void* or vice versa? As a result of the integer division 3/2 we get the value 1, which is of the int type. Note the difference between the type casting of a variable and type casting of a pointer. ncdu: What's going on with this second size column? casting from int to void* and back to int. cast to void *' from smaller integer type 'int Casting int to void* : r/C_Programming - reddit To learn more, see our tips on writing great answers. itch" "-I..\include\windows" "-Iinclude" "-I..\include" "-I..\datapath-windows\include" "-IC:\PTHREADS-BUILT\include" "-Xclang" "-fcolor-diagnostics" "-pipe" p-util.c.obj "-c" ../lib/odp-util.c 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 Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. Now, what happens when I run it with the thread sanitizer? The program can be set in such a way to ask the user to inform the type of data and . There is no "correct" way to store a 64-bit pointer in an 32-bit integer. Noncompliant Code Example (memset())For historical reasons, certain C Standard functions accept an argument of type int and convert it to either unsigned char or plain char. pthread passes the argument as a void*. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? All character types are to be converted to an integer. To learn more, see our tips on writing great answers. @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? lexborisov Modest Public. C++ how to get the address stored in a void pointer? LLNL's tutorial is bad and they should feel bad. rev2023.3.3.43278. @Xax: Here's a fixed version, without the race condition: gist.github.com/depp/241d6f839b799042c409, gist.github.com/depp/3f04508a88a114734195, How Intuit democratizes AI development across teams through reusability. for (i=0, j=0; j Typecasting - Data Types - Language Basics - MQL4 Reference If you preorder a special airline meal (e.g. And then assign it to the double variable. Remarks. That's probably going to be true for most platforms you will ever encounter, but it's not a guarantee; it's implementation-dependent. error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. 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. Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin? You are getting warnings due to casting a void* to a type of a different size. windows meson: cast to 'HANDLE' (aka 'void *') from smaller integer Where does this (supposedly) Gibson quote come from? Since gcc compiles that you are performing arithmetic between void* and an int (1024). error: cast from pointer to smaller type 'unsigned int' loses I am an entry level C programmer. From the question I presume the OP does. Please help me compile Chez Scheme. (int) pthread_self() 64int48intuintptr_t (unsigned int) 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 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. My code is all over the place now but I appreciate you all helping me on my journey to mastery! Usually that means the pointer is allocated with. unsigned long call_fn = (unsigned long)FUNC; This is flat out wrong. Can I tell police to wait and call a lawyer when served with a search warrant? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. this question. Again, all of the answers above missed the point badly. void* to an array - C++ Forum - cplusplus.com A nit: in your version, the cast to void * is unnecessary. How Intuit democratizes AI development across teams through reusability. 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. SCAN_PUT_ATTR(mask, ATTR, smask, FUNC); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ static_cast conversion - cppreference.com Is pthread_join a must when using pthread in linux? c - How to cast an integer to void pointer? - Stack Overflow Most answers just try to extract 32 useless bits out of the argument. Changing the type of ids would be the cleanest solution, but I decided against it when being confronted with this issue myself, as it only introduced a lot of issues with other code that is relying on ids being an int-array. If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. Even if you are compiling your program for a 32-bit computer, you should fix your code to remove these warnings, to ensure your code is easily portable to 64-bit. But this code pass the normal variable .. 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;. Your first example is risky because you have to be very careful about the object lifetimes. What video game is Charlie playing in Poker Face S01E07? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. Java Type Casting (With Examples) - Programiz This page was last modified on 12 February 2023, at 18:25. If the destination type is bool, this is a boolean conversion (see below). You use the address-of operator & to do that. Recovering from a blunder I made while emailing a professor. XCode 5.1 is change all architecture to 64 bit. I'm trying to create a void* from an int. Implementing From will result in the Into implementation but not vice-versa. vegan) just to try it, does this inconvenience the caterers and staff? you can just change architecture to support 32 bit compilation by all below in in Build Settings. Notifications. Replacing broken pins/legs on a DIP IC package, AC Op-amp integrator with DC Gain Control in LTspice. 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. Asking for help, clarification, or responding to other answers. [PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type warning This will only compile if the destination type is long enough. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. reinterpret_cast conversion - cppreference.com What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? The pointer doesn't actually point to anything, but it's the result of an earlier cast from an integer to a pointer (e.g. Not the answer you're looking for? Does Counterspell prevent from any further spells being cast on a given turn? However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. void* -> integer -> void* rather than integer -> void* -> integer. return ((void **) returnPtr);} /* Matrix() */. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. So,solution #3 works just fine. Otherwise, if the original pointer value points to an object a, and there is an object b of the . Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. How to use Slater Type Orbitals as a basis functions in matrix method correctly? This is why you got Error 1 C2036, from your post. 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. Making statements based on opinion; back them up with references or personal experience. The result is the same as implicit conversion from the enum's underlying type to the destination type. In such a case the programmer can use a void pointer to point to the location of the unknown data type. What is the difference between const int*, const int * const, and int const *? What is the correct method to cast an int to a void*? What is the point of Thrower's Bandolier? What is the purpose of non-series Shimano components? You may declare a const int variable and cast its reference to the void*. It's an int type guaranteed to be big enough to contain a pointer. This is not even remotely "the correct answer". STR34-C. Connect and share knowledge within a single location that is structured and easy to search. It is commonly called a pointer to T and its type is T*. Casting type int to const void* - C / C++ 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. Converting a void* to an int is non-portable way that may work or may not! 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. I have a two functions, one that returns an int, and one that takes a const void* as an argument. Typically, long or unsigned long is . FAILED: lib/libopenvswitch.a.p/odp-util.c.obj By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. this way you won't get any warning. Not the answer you're looking for? But I don't want to edit code in "EAGLView.mm" because it's a "library file". BUT converting a pointer to void* and back again is well supported (everywhere). The following program casts a double to an int. 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; Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). Don't do that. In this case, casting the pointer back to an integer is meaningless, because . Implicit Type Conversion in C with Examples - GeeksforGeeks The most general answer is - in no way. 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. This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. How to convert a factor to integer\numeric without loss of information? clang11 report error: cast to smaller integer type #82 - GitHub rev2023.3.3.43278. The correct answer is, if one does not mind losing data precision. Narrowing Casting (manually) - converting a larger type to a . actually no, as int my be a smaller type than a pointer ;-) But, of course with int64_t it works fine. Click to see the query in the CodeQL repository. Replacing broken pins/legs on a DIP IC package, How to handle a hobby that makes income in US. Implicit conversions - cppreference.com [mst-vhost:vhost 5/52] drivers/block/virtio_blk.c:539:21: warning 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 notate a grace note at the start of a bar with lilypond? What is the purpose of non-series Shimano components? Fork 63. You are right! How to use Slater Type Orbitals as a basis functions in matrix method correctly? To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. x is a local variable and its lifetime ends as soon as control leaves the scope it was defined in. Windows has 32 bit long only on 64 bit as well. You can only do this if you use a synchronization primitive to ensure that there is no race condition. @BlueMoon Thanks a lot! rev2023.3.3.43278. Whats the grammar of "For those whose stories they are"? If the value is ever used as pointer again that will prove to be an extremely bad idea. 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. Therefore it is perfectly valid for the compiler to throw an error for a line like. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. Acidity of alcohols and basicity of amines. A long long would not work for 32bit systems and a long would not work for 64 bit Windows (while 64bit Unix and Unix-like systems like OS X use the LP64 data model, in which a long is 64bit, 64bit Windows uses the LLP64 data model, in which a long has a size of 32bit (http://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models)). I assumed that gcc makes a 65536 out of my define, but I was wrong. In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. What happens if you typecast as unsigned first? It's always a good practice to put your #define's in brackets to avoid such surprise. Then i can continue compiling. 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. Properly casting a `void*` to an integer in C++ 24,193 Solution 1 I think using intptr_t is the correct intermediate here, since it's guaranteed to be large enough to contain the integral value of the void*, and once I have an integer value I can then truncate it without causing the compiler to complain. Thanks for contributing an answer to Stack Overflow! Are there tables of wastage rates for different fruit and veg? In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. - the incident has nothing to do with me; can I use this this way? ^~~~~~~~~~~~~~~~~~~~~ It is purely a compile-time directive which instructs the compiler to treat expression as if it had . Why is there a voltage on my HDMI and coaxial cables? Bulk update symbol size units from mm to map units in rule-based symbology. property that any valid pointer to void can be converted to this type, By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. ../lib/odp-util.c:5489:33: note: expanded from macro 'SCAN_PUT_ATTR' You could use this code, and it would do the same thing as casting ptr to (char*). You can fix this error by replacing this line of code. If pointers are 64 bits and ints are 32 bits, an int is too small to hold a pointer value. How can this new ban on drag possibly be considered constitutional? Implicit Type Conversion is also known as 'automatic type conversion'. } SCAN_END_SINGLE(ATTR) Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. windows meson: cast to smaller integer type 'unsigned long' from 'void If your standard library (even if it is not C99) happens to provide these types - use them. 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.

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