u32 -> u8) will truncate Casting from a smaller integer to a larger integer (e.g. 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;. Connect and share knowledge within a single location that is structured and easy to search. Embedded hyperlinks in a thesis or research paper. 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. Run this code to find how Java handles division and what casting can do to the results. Why does setupterm terminate the program? The most general answer is in no way. Did the drapes in old theatres actually say "ASBESTOS" on them? value of malloc is bad, like: That's not a good idea if the original object (that was cast to void*) was an integer. In C (int)b is called an explicit conversion, i.e. Can anybody explain how to pass an integer to a function which receives (void * ) as a parameter? Thus as a result it may be less error prone to generate a pointer dynamcially and use that. i Connect and share knowledge within a single location that is structured and easy to search. it often does reinterpret_cast<uint32_t> (ptr). 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. There are ways to prevent this: pass a dynamic allocated argument if your not the passing thread is not static or if your argument is a local variable, otherwise there is no issue. Boolean algebra of the lattice of subspaces of a vector space? If your standard library (even if it is not C99) happens to provide these types - use them. This is what the second warning is telling you. For more information, see the Conversions section of the C# language specification. There is no "correct" way to store a 64-bit pointer in an 32-bit integer. He also rips off an arm to use as a sword, Two MacBook Pro with same model number (A1286) but different year. replace uint32_t by uintptr_t wholesale, then fix remaining cases one by one. User-defined conversions: User-defined conversions are performed by special methods that you can define to enable explicit and implicit conversions between custom types that do not have a base classderived class relationship. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. rev2023.5.1.43405. Not the answer you're looking for? How can I control PNP and NPN transistors together from one pin? @ck_ I didn't realize the error in the question is actually an error by default, not a warning-turned-error. how about using uintptr_t, most of your pointer arithmetic may still works. Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. The reinterpret_cast makes the int the size of a pointer and the warning will stop. The next Access Europe Meeting is on Wed 3 May 2023. It is safer to not make assumptions, but rather check the type. Find centralized, trusted content and collaborate around the technologies you use most. How do I force make/GCC to show me the commands? Does a password policy with a restriction of repeated characters increase security? We have to pass address of the variable to the function because in function definition argument is pointer variable. Can I use my Coinbase address to receive bitcoin? Making statements based on opinion; back them up with references or personal experience. However, this specific error is not due to a warning and I can't find any option to disable errors (makes sense, since most errors are fatal). It's an int type guaranteed to be big enough to contain a pointer. Integer conversions, both implicit and explicit (using a cast), must be guaranteed not to result in lost or misinterpreted data. 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. But gcc always give me a warning, that i cannot cast an int to a void*. Why don't we use the 7805 for car phone chargers? You need to cast the void* pointer to a char* pointer - and then dereference that char* pointer to give you the char that it points to! what does it mean to convert int to void* or vice versa? eg. How create a simple program using threads in C? I agree that you should bite the bullet and fix the code to use the correct integer type. C99 defines the types "intptr_t" and "uintptr_t" which do . They should do their job unless your code is too tricky. There's no proper way to cast this to int in general case. This is not a conversion at all. @Xax: Here's a fixed version, without the race condition: gist.github.com/depp/241d6f839b799042c409, gist.github.com/depp/3f04508a88a114734195, How a top-ranked engineering school reimagined CS curriculum (Ep. What were the most popular text editors for MS-DOS in the 1980s? Why are players required to record the moves in World Championship Classical games? return ((void **) returnPtr);} /* Matrix() */. So make sure you understand what you are doing! Making statements based on opinion; back them up with references or personal experience. again. Why did US v. Assange skip the court of appeal? Or you might need to assign a class variable to a variable of an interface type. following block Hello, Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? Question is, how do I explain this to Clang? . Rep Power: 3. Alternatively, if you choose to castthe ptr variableto (size_t) instead, then you don't need to worry about the pointer typeanymore. Therefore, you need to change it to long long instead of long in windows for 64 bits. Is pthread_join a must when using pthread in linux? Is there any known 80-bit collision attack? 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. @DietrichEpp can you explain what is race condition with using. @DavidHeffernan I rephrased that sentence a little. No special syntax is necessary because a derived class always contains all the members of a base class. Don't do that. 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. The best way is, if one can, do not do such casting, instead, if the same memory address has to be shared for pointer and int (e.g. casting from int to void* and back to int. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. You think by casting it here that you are avoiding the problem! C# provides the is operator to enable you to test for compatibility before actually performing a cast. 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. Expressions Converts between types using a combination of implicit and user-defined conversions. this way I convert an int to a void* which is much better than converting a void* to an int. Remembering to delete the pointer after use so that we don't leak. The compiler is perfectly correct & accurate! Keep in mind that thrArg should exist till the myFcn() uses it. 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. Syntax static_cast< new-type > ( expression ) Returns a value of type new-type . 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 396k 35 399 609 1 Just edited. However, I believe that even if the define was for the "65536", it would not be what @kaetzacoatl wanted. How a top-ranked engineering school reimagined CS curriculum (Ep. Solution 1. The content you requested has been removed. Folder's list view has different sized fonts in different folders. Not the answer you're looking for? On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. No idea how it amassed 27 upvotes?! When do you use in the accusative case? @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. Join Bytes to post your question to a community of 472,246 software developers and data experts. The error I'm getting is: error: cast from pointer to smaller type 'uint32_t' (aka 'unsigned int') loses information. 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. Asking for help, clarification, or responding to other answers. 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. I was able to disable this with -fms-extensions after getting this from someone on the Cpplang Slack: Looking at "DiagnosticSemaKinds.td" it shows up as err_bad_reinterpret_cast_small_int, https://github.com/llvm-mirror/clang/blob/release_50/include/clang/Basic/DiagnosticSemaKinds.td#L6193 /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, xcode build error: Semantic issue cast from pointer to smaller type 'int' loses information. @ok Youll be auto redirected in 1 second. void *ptr; int n = (int)ptr; So in c++ i tried below int n = atoi (static_cast<const char*> (ptr)); This crashes when i run. Does it effect my blogs SEO rankings? I'm trying to create a void* from an int. That could create all kinds of trouble. 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). I cannot reverse my upvote of user384706's answer, but it's wrong. @Shahbaz you could but I will not suggest to a C newbie to use globals. But you seem to suggest by your answer that the user can pass 5 to pthread_create and then perform the above cast to get it back. rev2023.5.1.43405. ", "!"? I am looking to clean up the Going through them one by one would be very tedious and since this is an experimental project anyway, I'm happy to settle for a "hackish" workaround. If the types are from the same inheritance tree, then you should either use dynamic_casts or even better, you should benefit from dynamic dispatching.. dynamic_cast is slightly better, but still should be avoided. If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. property that any valid pointer to void can be converted to this type, Save this piece of code as mycast.hpp and add -include mycast.hpp to your Makefile. Generating points along line with specifying the origin of point generation in QGIS. If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? Therefore, after you declare i as an int, you cannot assign the string "Hello" to it, as the following code shows: However, you might sometimes need to copy a value into a variable or method parameter of another type. Convert integers, floating-point values and enum types to enum types. ', referring to the nuclear power plant in Ignalina, mean? Becase one can always legally cast any Hello, Is "I didn't think it was serious" usually a good defence against "duty to rescue"? You might want to typedef, You should change your code to handle this. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, error: cast from void* to int loses precision, cast to pointer from integer of different size, pthread code. A boy can regenerate, so demons eat him for years. How to force Unity Editor/TestRunner to run at full speed when in background? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. last post by: I'm looking for the name of the following casting style in order to do By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. But to answer your question: No, you can't disable it, though you can work around it. Not the answer you're looking for? Yes, for the reason you mentioned that's the proper intermediate type. 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. Can I use my Coinbase address to receive bitcoin? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Casting is required when information might be lost in the conversion, or when the conversion might not succeed for other reasons. This code is a bit odd (but a void* can certainly host a int on all architectures on which GDAL can be compiled), and certainly unused by anyone, so you could just remove the GetInternalHandle () implementation as well if you prefer. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. 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;. Many errors come from warnings. Two MacBook Pro with same model number (A1286) but different year. For built-in numeric types, an implicit conversion can be made when the value to be stored can fit into the variable without being truncated or rounded off. Offline ImPer Westermark over 12 years ago in reply to Andy Neil Except that you sometimes stores an integer in the pointer itself. The program will not compile without the cast. Why does flowing off the end of a non-void function without returning a value not produce a compiler error? Put your define inside a bracket: without a problem. #, In a 64 bit machine with sizeof(int) == 4. If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. Most answers just try to extract 32 useless bits out of the argument. For reference types, an implicit conversion always exists from a class to any one of its direct or indirect base classes or interfaces. Find centralized, trusted content and collaborate around the technologies you use most. cast to void *' from smaller integer type 'int cast to void *' from smaller integer type 'int. By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use. 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). You may declare a const int variable and cast its reference to the void*. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. struct foo *foo; Typical examples include numeric conversion to a type that has less precision or a smaller range, and conversion of a base-class instance to a derived class. Half your pointer will be garbage. The casting operators (int) and (double) are used right next to a number or variable to create a temporary value converted to a different data type. Who has a solution to casting from int to void* and back to int, http://www.ungerhu.com/jxh/clc.welcome.txt, http://benpfaff.org/writings/clc/off-topic.html. I don't understand why the following two cases produce different Hi, I've this question: suppose we have two differently typed pointers: 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 For a complete list of supported explicit numeric conversions, see the Explicit numeric conversions section of the Built-in numeric conversions article. How do I check if a string represents a number (float or int)? 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. rev2023.5.1.43405. From that point on, you are dealing with 32 bits. Write values of different data types in sequence in memory? In the realm of Android development, two languages have consistently stood out: Java and Kotlin. @DavidHeffernan, sane thread APIs wouldn't send integral data to the thread procedures, they would send pointers. The main point is: a pointer has a platform dependent size. 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; Is a downhill scooter lighter than a downhill MTB with same performance? You can then disable this diagnostic completely by adding -Wno-extra-tokens (again, the "extra tokens" warning is an example), or turn it into a non-fatal warning by means of -Wno-error=extra-tokens. If we had a video livestream of a clock being sent to Mars, what would we see? 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". Which was the first Sci-Fi story to predict obnoxious "robo calls"? To avoid truncating your pointer, cast it to a type of identical size. For more information, see Polymorphism. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. and how to print the thread id of 2d array argument? then converted back to pointer to void, and the result will compare C++ how to get the address stored in a void pointer? As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. Can I use the spell Immovable Object to create a castle which floats above the clouds? The following program casts a double to an int. static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). And in this context, it is very very very common to see programmers lazily type cast the. Thanks for contributing an answer to Stack Overflow! My code is all over the place now but I appreciate you all helping me on my journey to mastery! Connect and share knowledge within a single location that is structured and easy to search. From: Hans de Goede <hdegoede@redhat.com> To: Mark Gross <mgross@linux.intel.com> Cc: Hans de Goede <hdegoede@redhat.com>, Andy Shevchenko <andy@infradead.org>, platform-driver-x86@vger.kernel.org, kernel test robot <lkp@intel.com> Subject: [PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type warning Date: Mon, 23 Jan 2023 14:28:24 +0100 [thread overview] Message-ID: <20230123132824. . You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : 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; How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. # * # (intptr_t) # # warning: cast to pointer from integer of different size # (intptr_t)IDE # (void*) . Casting arguments inside the function is a lot safer. Wrong. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, Setting a buffer of char* with intermediate casting to int*. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? Which ability is most related to insanity: Wisdom, Charisma, Constitution, or Intelligence? But then you need to cast your arguments inside your thread function which is quite unsafe cf. On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. What I am trying to do in that line of code is check to make sure each character in my string is alphabetical. Now, what happens when I run it with the thread sanitizer? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. There is absolutely not gurantee that sizeof(int) <= sizeof(void*). 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'll edit accordingly. As shown in the following example, a type cast that fails at run time will cause an InvalidCastException to be thrown. 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 a top-ranked engineering school reimagined CS curriculum (Ep. Asking for help, clarification, or responding to other answers. For integral types, this means the range of the source type is a proper subset of the range for the target type. Episode about a group who book passage on a space ship controlled by an AI, who turns out to be a human who can't leave his ship? A cast is a way of explicitly informing the compiler that you intend to make the conversion and that you are aware that data loss might occur, or the cast may fail at run time. 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. For reference types, an explicit cast is required if you need to convert from a base type to a derived type: A cast operation between reference types does not change the run-time type of the underlying object; it only changes the type of the value that is being used as a reference to that object. Was Aristarchus the first to propose heliocentrism? A cast is a way of explicitly informing the compiler that you intend to make the conversion and that you are aware that data loss might occur, or the cast may fail at run time. However, if a conversion cannot be made without a risk of losing information, the compiler requires that you perform an explicit conversion, which is called a cast. For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. How to convert a factor to integer\numeric without loss of information? The error message mentions the diagnostic responsible for error message, e.g. For example, a variable of type long (64-bit integer) can store any value that an int (32-bit integer) can store. Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? In this case, casting the pointer back to an integer is meaningless, because . More info about Internet Explorer and Microsoft Edge, How to convert between hexadecimal strings and numeric types, How to safely cast using pattern matching and the as and is operators.