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. Why did US v. Assange skip the court of appeal? Could a subterranean river or aquifer generate enough continuous momentum to power a waterwheel for the purpose of producing electricity? How do I check if a string represents a number (float or int)? Interpreting non-statistically significant results: Do we have "no evidence" or "insufficient evidence" to reject the null? How to cast a void pointer to any other type in C || #C Programming language || Coding is Life 487 03 : 37 Unable to cast object of type 'System DateTime' to type 'System String' SharpCoder 336 10 : 53 Tkinter window geometry to manage height width and zoom out using state and resizable () option plus2net 107 Author by david.brazdil The program will not compile without the cast. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. static_cast conversion - cppreference.com Integer conversions, both implicit and explicit (using a cast), must be guaranteed not to result in lost or misinterpreted data. The following program casts a double to an int. 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. Then he wants to convert px to Hello, If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. Unfortunately, that hardware is 64-bit and the code contains many instances of pointer arithmetic that expects pointers to be 32-bit, i.e. rev2023.5.1.43405. 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. 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. this question. this way you won't get any warning. Examples include conversions from smaller to larger integral types, and conversions from derived classes to base classes. Can anybody explain how to pass an integer to a function which receives (void * ) as a parameter? I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. This forum has migrated to Microsoft Q&A. How to correctly type cast (void*)? - social.msdn.microsoft.com To subscribe to this RSS feed, copy and paste this URL into your RSS reader. He also rips off an arm to use as a sword, Two MacBook Pro with same model number (A1286) but different year. 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. Nov 14 '05 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. return ((void **) returnPtr);} /* Matrix() */. There are two occurences in "SemaCast.cpp" -- one of which suggests it's sensitive to MS extensions, https://github.com/llvm-mirror/clang/blob/release_50/lib/Sema/SemaCast.cpp#L2112 Once you manage to make this cast, then what?! Canadian of Polish descent travel to Poland with Canadian passport. So make sure you understand what you are doing! That's not a good idea if the original object (that was cast to void*) was an integer. Find centralized, trusted content and collaborate around the technologies you use most. What is the symbol (which looks similar to an equals sign) called? rev2023.5.1.43405. Remembering to delete the pointer after use so that we don't leak. again. Why did US v. Assange skip the court of appeal? even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. Passing negative parameters to a wolframscript, Generating points along line with specifying the origin of point generation in QGIS. Widening or Automatic Type Conversion Please help me with the right way to convert void* to int in c++ Mar 30, 2020 at 10:44am George P (5286) Maybe try reinterpret_cast? Is "I didn't think it was serious" usually a good defence against "duty to rescue"? Storage management is an important module of database, which can be subdivided into memory management and external memory management. 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. Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? c printf() C , {} . The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. Wrong. casting from int to void* and back to int. If you write ((char*)ptr + 1), it will advance the pointer 1 byte, because a "char" is 1 byte. Yes, for the reason you mentioned that's the proper intermediate type. UDF for multiples heterogenous reactions - CFD Online Put your define inside a bracket: without a problem. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Does a password policy with a restriction of repeated characters increase security? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. 23.04.27, ICP15005796-233010602002000ICP B2-20201554. Hello, I am currently working on a UDF for the heterogeneous reaction using it to describe a simple equilibrium model using the Antoine equation and vapor pressure. How can I control PNP and NPN transistors together from one pin? This allows you to reinterpret the void * as an int. We have to pass address of the variable to the function because in function definition argument is pointer variable. When is casting void pointer needed in C? how about using uintptr_t, most of your pointer arithmetic may still works. The error message mentions the diagnostic responsible for error message, e.g. To avoid truncating your pointer, cast it to a type of identical size. 1) zero or one conversion from the following set: lvalue-to-rvalue conversion, array-to-pointer conversion, and function-to-pointer conversion; 2) zero or one numeric promotion or numeric conversion; 3) zero or one function pointer conversion; (since C++17) 4) zero or one qualification conversion. Should I re-do this cinched PEX connection? 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. 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. . For example, (double) 1/3 will give a double result instead of an int one. (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. u32 -> u8) will truncate Casting from a smaller integer to a larger integer (e.g. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. reinterpret_cast<void *>(42)). 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. A nit: in your version, the cast to void * is unnecessary. what does it mean to convert int to void* or vice versa? Did the drapes in old theatres actually say "ASBESTOS" on them? 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! Interpreting non-statistically significant results: Do we have "no evidence" or "insufficient evidence" to reject the null? Ubuntu won't accept my choice of password, Adding EV Charger (100A) in secondary panel (100A) fed off main (200A), Passing negative parameters to a wolframscript. Not the answer you're looking for? Basically its a better version of (void *)i. equal to the original pointer: First you are using a define, which is not a variable. to the original pointer: The following type designates an unsigned integer type with the 1.6. Casting and Ranges of Variables AP CSAwesome I want to learn the difference between the three type cast operators: Hi, 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. 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, Short story about swapping bodies as a job; the person who hires the main character misuses his body. Can I use my Coinbase address to receive bitcoin? Terrible solution. Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. For example, the string cannot be implicitly converted to int. Not the answer you're looking for? Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). How a top-ranked engineering school reimagined CS curriculum (Ep. How to cast/convert pointer to reference in C++, clang error: unknown argument: '-mno-fused-madd' (python package installation failure). I saw on a couple of recent posts people saying that casting the return arduino ide - Incompatible types in assignment of 'uint8_t {aka that any valid pointer to void can be converted to this type, then Is there any known 80-bit collision attack? Asking for help, clarification, or responding to other answers. What is this brick with a round back and a stud on the side used for? Short story about swapping bodies as a job; the person who hires the main character misuses his body. 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. 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. For more information, see User-defined conversion operators. What would you do next year when you need to port it to yet another experimental hardware? Connect and share knowledge within a single location that is structured and easy to search. If we had a video livestream of a clock being sent to Mars, what would we see? a cast of which the programmer should be aware of what (s)he is doing. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. 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? 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. My blogs h2 and other tags are in these manner. [PATCH] platform/x86: hp-wmi: Fix cast to smaller integer type warning A. if(x%2=1)y=x;B. if(sqrt(x)%2)y=x;C. if(x==1)y=x;D. if(x==1)y=&x; Cerror: cast to 'void *' from smaller integer type 'int'. arrays - I get the error: "cast to smaller integer type 'int' from To learn more, see our tips on writing great answers. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. 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. C++ how to get the address stored in a void pointer? Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. Posted on Author Author 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;. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, I would try to fix the code instead. Casting arguments inside the function is a lot safer. (i.e. I hit this same problem in a project without C++11, and worked around it like this: Thanks for contributing an answer to Stack Overflow! cast to void *' from smaller integer type 'int-tdecu credit scoretdecu credit score The problem is not with casting, but with the target type loosing half of the pointer. Why did DOS-based Windows require HIMEM.SYS to boot? #, Nov 14 '05 If the data types are compatible, then Java will perform the conversion automatically known as Automatic Type Conversion, and if not then they need to be cast or converted explicitly. 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. Folder's list view has different sized fonts in different folders. Thanks for pointing that out. Keep in mind that thrArg should exist till the myFcn() uses it. 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. Even though what you say regarding the lifetime of the object is true, integral types are too limited for a generic API. How to set, clear, and toggle a single bit? 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. I think that's what you want: // Declaration uint8_t *myData; void loop () { myData = "custom string"; } rev2023.5.1.43405. If you are going to pass the address you typically need to exert some more control over the lifetime of the object. I assumed that gcc makes a 65536 out of my define, but I was wrong. The semantics of numeric casts are: Casting between two integers of the same size (e.g. What differentiates living as mere roommates from living in a marriage-like relationship? For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. EXP36-C. Do not cast pointers into more strictly aligned pointer types Thank you all for your feedback. It is safer to not make assumptions, but rather check the type. From that point on, you are dealing with 32 bits. Usually that means the pointer is allocated with. pthread passes the argument as a void*. It keeps throwing this exact error message even though both types are 32 bits wide. i cast to void *' from smaller integer type 'int Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? I'm having a little bit of trouble regarding pointer casting in my program. Canadian of Polish descent travel to Poland with Canadian passport, Two MacBook Pro with same model number (A1286) but different year, Folder's list view has different sized fonts in different folders. So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. @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. 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. You think by casting it here that you are avoiding the problem! ERROR: incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int', error: cast to 'string' (aka 'char *') from smaller integer type 'int' [-Werror,-Wint-to-pointer-cast], error: incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int' C, warning: initialization of 'unsigned char' from 'uint8_t *' {aka 'unsigned char *'} makes integer from pointer without a cast [-Wint-conversion], Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. You can use any other pointer, or you can use (size_t), which is 64 bits. What were the most popular text editors for MS-DOS in the 1980s? Say I want to make 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. Convert integers, floating-point values and enum types to enum types. casting from int to void* and back to int - C / C++ To subscribe to this RSS feed, copy and paste this URL into your RSS reader. How to correctly cast a pointer to int in a 64-bit application? The most general answer is - in no way. How to correctly cast a pointer to int in a 64-bit application? (void *)i Error: cast to 'void *' from smaller integer type 'int', PS: UBUNTUCLANG3.5 clang -O0 -std=gnu11 -march=native -lm -lpthread pagerank.c -o pagerank, , i What is this brick with a round back and a stud on the side used for? this way you won't get any warning. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. Please unaccept the answer you have chosen as it is wrong (as the comments below it say) and will lead to bugs. Why does Acts not mention the deaths of Peter and Paul? Is "I didn't think it was serious" usually a good defence against "duty to rescue"? Cerror: cast to 'void *' from smaller integer type 'int Making statements based on opinion; back them up with references or personal experience. 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. pointer/reference to a derived class pointer/reference. It's always a good practice to put your #define's in brackets to avoid such surprise. Can my creature spell be countered if I cast a split second spell after it? 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. Say you hack this successfully. d=(double *) Hi, cast to void *' from smaller integer type 'int I agree that you should bite the bullet and fix the code to use the correct integer type. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : This option of Python is missing in matplotlibcpp within Visual Studio -> works only in b/w ! You can insert some debugging/logging logic to Reinterpret_cast if necessary. This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). C99 defines the types "intptr_t" and "uintptr_t" which do . In some reference type conversions, the compiler cannot determine whether a cast will be valid. Since gcc compiles that you are performing arithmetic between void* and an int (1024). Making statements based on opinion; back them up with references or personal experience. @DavidHeffernan I rephrased that sentence a little. eg. Connect and share knowledge within a single location that is structured and easy to search. does lazarbeam have a wife; Books. 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.
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