, https://blog.csdn.net/drzeno/article/details/105218386, C++ (const_cast/reinterpret_cast), matplotlib.lines.Line2D object at 0x7f68cfd5a2e8, RuntimeError: mat1 dim 1 must match mat2 dim 0local variable beta1 referenced before assignment. How many transistors at minimum do you need to build a general-purpose computer? class base Do non-Segwit nodes reject Segwit transactions with invalid signature? printf("%d",c); Does the collective noun "parliament of owls" originate in "parliament of fowls"? C++ how to get the address stored in a void pointer? Do bracers of armor stack with magic armor enhancements and special abilities? b->disp(); A WORD is 16 bits, and a size_t is usually 32 or 64 bits depending on the compiler options, the same size as a pointer with the same options. So eg: I'm not going to weigh in on whether it's right or wrong to abuse a void* this way. 5() If the reason for the cast is to make the pointer opaque, then void* already achieves this, so the code could use void* instead of int. int i; i = (int)(tulong)ptr; I think, the problem is of typecasting a pointer to a shorter data type. { Can any one tell me why my following program is crashing? Terrible solution. cout << CA::i << endl; From the question I presume the OP does. Here c returns some junk value. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. virtual void disp() I am sorry, but this is not a valid solution. I would create a structure and pass that as void* to pthread_create. This means you. This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. void my machine details The issue is that, in 32bits, an int (which is a 32bit integer) will hold a pointer value. struct a{ unsigned int b=10; Of course, it is better to master the type conversion by explicit cast. Hi, What do you think will happen when you try to store a 64-bit wide pointer into a 32-bit integer? But once you get an address > 4GB, your code will start 'mysteriously' not working. b->disp(); Devesh. class base I type this to compile: Size of pointer may be greater than size of int and depends of memory model. +1 for referencing intptr_t. Thanks for contributing an answer to Stack Overflow! char *ptr; // Even if the compiler wouldn't give an error the code most likely wouldn't work. How can I randomly select an item from a list? Is there any reason on passenger airliners not to have a physical lock between throttles? }; d->disp(); # I have used My question is simple: When should I use a long, int, char, unsigned/signed variables?? 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. Do bracers of armor stack with magic armor enhancements and special abilities? 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. hi, derv *d; How do you exit from a void function in C++? If you convert ( void*) to ( long) no precision is lost, then by assigning the ( long) to an ( int ), it properly For C++ I'd normally advise using C++ I/O with the << operator (and for pointers you have to be careful with char*, which has an overload treating it as a pointer to a string), but that might not be available in this case. No idea how it amassed 27 upvotes?! public: I want to compile this example program in order to embed Python in C ++. It has a parameter called backlog and it limits the maximum length of queue of pending list. rev2022.12.9.43105. is int64_t or u_int64_t what I need ? Insertion will be allowed, but accessing or searching may be problematic due to compilation error. }; The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. As defined by the current C++ standard, there is no integer type which is guaranteed to hold a pointer. {cout<<"from der\n";} virtual void disp() Before invalidating anything, please always consider the requirement first. How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? Can you please explain it with suitable example. printf("%d",c); How many transistors at minimum do you need to build a general-purpose computer? 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. You have to manually edit those files in order to replace them with code that isn't likely to be buggy and nonportable. At what point in the prequels is it revealed that Palpatine is Darth Sidious? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Is there a compiler flag to suppress these errors? Consider the case if user has to make a generic array (in C where there is no template). How to cast an int unique_ptr into a void unique_ptr? Should my function return a pointer to std::vector, or a reference to std::vector? #include To learn more, see our tips on writing great answers. # sign.sh I just came across some code doing the same thing - yeah, its not great but needed a solution to get it compiling on 64 bit machines - thanks for the heads-up! #/bin/bash When you move to 64bit, you can no longer store a pointer in an int - it isn't large enough to hold a 64bit pointer. You have to manually edit those files in order to replace them with code that isn't likely to be buggy and nonportable. tell me. cannot convert argument 1 from int to int && error. We are migrating our c-code to 10.2.0.3.0. Casting a pointer to void* and back is valid use of reinterpret_cast<>. On 64-bit systems, the cast doesn't work. Linux Man Pages, cast from const void* to unsigned int loses precision, difference between int ** func() and int *& func(), to get the correct value with unsigned int, Help - Cast converts default int return type. using namespace std; Sometimes it is sensible to want to split up a 64-bit item into 2 32-bit items. If the sizes are different then endianess comes into play. Ready to optimize your JavaScript with Rust? Is Making statements based on opinion; back them up with references or personal experience. (8) As defined by the current C++ standard, there is no integer type which is guaranteed to hold a pointer. Why doesn't my cast from enum to int work in release builds? But there be some circumstances where one can safely downcast pointer (e.g. 8 seconds for regex_match("", regex(".{40000}"));? @Wexxor: No, the point is that the a pointer has a different size than an. I disagree with the one-sidedness of all these answers. 1. As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). Is it safe to cast to int from std::round? The type int(32bit) is not big enough to hold 64 bit pointer void*. void disp() Connect and share knowledge within a single location that is structured and easy to search. Can any one tell me why my following program is crashing? Is this an at-all realistic configuration for a DHC-2 Beaver? For gcc, the flag is -m64. This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). *pi = 9; Would salt mines, lakes or flats be reasonably found in high, snowy elevations? void disp() Some platforms will have an intptr_t, but this is not a standard feature of C++. Why would I delcare an integer "long" or "short" ( unsigned or signed)?? Why does my stock Samsung Galaxy phone/tablet lack some features compared to other Samsung Galaxy models? Login or Register to Ask a Question and Join Our Community, Login to Discuss or Reply to this Discussion in Our Community, All UNIX https://bbs.csdn.net/topics/603958740 int fileDescriptor; How should I handle cast from void* to int loses precision when compiling 32-bit code on 64-bit machine? int* pi = const_cast(&CA::i); The OP tried this directly, and your answer still does it, except that it converts to 64-bit integer first, and then to 32-bit integer. How does the Chameleon's Arcane/Divine focus interact with magic item crafting? Handle int listen(int sockfd, int backlog) in TCP, C++ program is crashing on re-assigning const static member variable using an int pointer, Help with understanding ( int, char, long, short, signed, unsigned etc. ). Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. Any examples of when things like "unsigned", "long", "short" etc Hi, Why cast a float to an integer? If the reason for the cast is to achieve compatibility with some existing library (perhaps an older callback interface) which cannot be modified, then I think you need to review the documentation for that library. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. "No appropriate default constructor available"--Why is the default constructor even called? This is why the stdint.h header was created, to allow you to explicitly state the size of the type you're using across many different platforms with many different word sizes. I am new to C. (used it some in college). Partitioning/batch/chunk a container into equal sized pieces using std algorithms. const int CA::i = 10; The best answer is still to fix the code, I suppose, but if it's legacy third-party code and these warnings are rampant, I can't see this refactoring as being a very efficient use of your time. Infact I know several systems where that does not hold. do Package: vlc Version: 0.8.4-svn20050810-1 Severity: serious Hi, Your package is failing to build on 64 bit arches with the following error: g++ -DHAVE_CONFIG_H -I. Please tell me We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. # I have used Login or Register to Ask a Question and Join Our Community, All UNIX public: If the function had the correct signature you would not need to cast it explicitly. Subtract key from that and you get a number corresponding to the address of There is no "correct" way to store a 64-bit pointer in an 32-bit integer. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. If I have three hello everybody! 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. Counterexamples to differentiation under integral sign, revisited. You do not want to suppress these errors because most likely, they are indicating a problem with the code logic. If you suppresses the errors, this int c1; eg. error: cast from void* to int loses precision. #include Or use long (is typically 64-bit on 64-bit platforms on the GCC compiler) or long long (a C99 types which most, but not all compilers, support in C++), or some other implementation-defined integral type that is at least 64 bits wide on a 64-bit platform. On your platform, a pointer does not fit in an int. We are migrating our c-code to 10.2.0.3.0. # Unsign to sign # sign.sh Should this static cast from int to double be avoided? Marcin Wrochniak Mon, 24 Oct 2005 23:48:12 -0700 Please help me with the following code to get the difference in values. or do I have to manually edit these files to avoid these casts? Help us identify new roles for community members, Proposing a Community-Specific Closure Reason for non-English content, Why is cast from X* to Y loses precision a hard error and what is suitable fix for legacy code, error: cast from 'void*' to 'int' loses precision, Missing include "bits/c++config.h" when cross compiling 64 bit program on 32 bit in Ubuntu. The example piece code below works perfectly except I agree passing a dynamically allocated pointer is fine (and I think the best way). Linux Man Pages, Help with understanding ( int, char, long, short, signed, unsigned etc. ), C++ program is crashing on re-assigning const static member variable using an int pointer, Handle int listen(int sockfd, int backlog) in TCP. You first convert to an integer type large enough to hold the pointer, and then you narrow it anyway. It seems you have a definition of size_t that is incorrect, you should fix it. Instead of using a long cast, you should cast to size_t. return(0); How can I store and/or print() a number that is larger than 4 294 967 295 in C? C++ deleting children basing on parent's pointer, Sending files over TCP sockets C++ | Windows. Connect and share knowledge within a single location that is structured and easy to search. How to set a newcommand to be incompressible by justification? The size of int is defined by the mix of compiler and architecture. How do I select rows from a DataFrame based on column values? Not sure if it was just me or something she sent to the whole team. Not the answer you're looking for? class derv : public base Bug#322955: wstools: FTBFS (amd64): cast from 'void*' to 'int' loses precision. Why is reading lines from stdin much slower in C++ than Python? Any examples of when things like "unsigned", "long", "short" etc Hi guys testhandlerint4. If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. int fileDescriptor; When I declare a variable "unsigned;" what did I do it??? I know that is unsafe and one must consider his/her logic before thinking of it. And, most of these will not even work on gcc4. Add a new light switch in line with another switch? rev2022.12.9.43105. To learn more, see our tips on writing great answers. If your standard library (even if it is not C99) happens to provide these types - use them. 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 am new to C. (used it some in college). As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. The most prominent warning is: hi, Ready to optimize your JavaScript with Rust? I want to create a file with permissions for read, write, and execute to everybody using C, so I write this code: Why would I delcare an integer "long" or "short" ( unsigned or signed)?? What is the POINTER_32 macro? Would it be possible, given current technology, ten years, and an infinite amount of money, to construct a 7,000 foot (2200 meter) aircraft carrier? listen(2): listen for connections on socket - Linux man page Where does the idea of selling dragon parts come from? The rubber protection cover does not pass through the hole in the rim. I see there may be other reasons. Copyright 2022 www.appsloveworld.com. fix cast from void* to Gluint 8a04369 gcc complained OsvrRenderingPlugin.cpp:788:44: error: cast from 'void*' to 'GLuint {aka unsigned int}' loses precision [-fpermissive] { The intptr_t type is designed for this. int is not, and converting a pointer to int can easily lose information. Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. }; Casting int to void* loses precision, and what is the solution in required cases, c++: cast from "const variable*" to "uint32" loses precision. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. . If your compiler defines intptr_t or uintptr_t, use those, as they are integer types guaranteed to be large enough to store a pointer. int x = (int)arg; use: int x = (long)arg; On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. int main(){ Casting from pointer to any data maybe useful in user-defined callbacks. }; Or stay on the 32-bit platform that the code currently works on. char d1; class derv : public base Yes, the code is not 64-bit clean. You could use this code, and it would do the same thing as casting ptr to (char*) returnPtr [j] = How do I parse a string to a float or int? class CA { int c1; I provide the solution if there is a dire need to cast pointer into integer. public: Multiplatform way to write a std::wstring into a file in C++, Forwarding references: reference parameter origin. How does legislative oversight work in Switzerland when there is technically no "opposition" in parliament? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. }. c = b - (unsigned int )sizeof(a); Then in such case, user can use void pointers to store any object. ric. char d1; c++ error when converting from hex string to int. cast from const void* to unsigned int loses precision. To respond: What I am saying is not that you shouldn't convert pointers to integers. cast from jobject to jboolean loses precision, C++ typecast: cast a pointer from void pointer to class pointer. This is likely to be the case with TThread::Printf as well. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. -1, Uggh. If I set backlog to 128, is it means no more than 128 packets can be handled by server? Please help me with the following code to get the difference in values. I faced similar problem. If I set backlog to 128, is it means no more than 128 packets can be handled by server? Pointer packing. Sorry, I had overlooked your previous reply to my comment. It's an int type guaranteed to be big enough to contain a pointer. , 1.1:1 2.VIPC, error: cast from void* to int loses precision. 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. main() I solved it in the following way: I think, the problem is of typecasting a pointer to a shorter data type. For a 64bit machine, it's tricky to cast an int pointer(hex format) to int value or char pointer to int value because each block of memory for an int variable is 32 bit and for char it's 8 bit. Int argument passed from C to Assembly loses its sign; What happens when a int list is cast as a char list in C? fileDescriptor = What does the warning message 724 "Cast converts default int return type to." I have a package that compiles and works fine on a 32-bit machine. while true { I want to create a file with permissions for read, write, and execute to everybody using C, so I write this code: Discussion at bytes.com. Casting a pointer to an int is horrible from a portability perspective. unsigned int c; long guarantees a pointer size on Linux on any machine. Hi guys } Asking for help, clarification, or responding to other answers. {cout<<"from der\n";} Why does the USA not have a constitutional court? difference between two pointers). Here c returns some junk value. Also, think why it is required? my solution is using "long long" instead of "int". base *b=new derv; What I am saying is that you shouldn't convert 64-bit pointers to 32-bit integers. How do I dynamically cast from a void * pointer generically? Is it illegal to use resources in a University lab to prove a concept could work (to ultimately use to create a startup). This detail is the reason why the conversion isn't allowed. const static int i; I am still in the search of a compiler option in GCC/Clang. The problem has nothing to do with your Makefile; it's an error in your C++ source code. const int CA::i = 10; If you see the "cross", you're on the right track. This is the valid case where this is required. } }; #include Actually, it's only likely to work well if it's in the first 2G - from 2~4G sign extension will get you :). That could create all kinds of trouble. class CA { Since 32 and 64 are both greater than 16, the compiler is complaining and rightly so. If the latter, then you need to 'downcast' that pointer back to an integer. Books that explain fundamental chess concepts. Definitely don't cast pointers to ints in any of your new code, though. The types uintptr_t and intptr_t, defined in or , are guaranteed to be able to hold a converted void* pointer value without loss of information (and will not be defined if no integer type qualifies). Because the system I compiled is linux64-bit, the pointer type and the long type are equal in size (8B) and the int type is 4B, so there will be: lost precision. Knowledge Base. In the best case this will give the same results as the original code, with no advantages, but in the worst case it will fail in multiple catastrophic ways (type punning, endianness, less efficient, etc. There's no proper way to cast this to int in general case. But the if( (. @Martin York: No, it doesn't depend on endiannness. Debian/Ubuntu - Is there a man page listing all the version codenames/numbers? c = b - (unsigned int )sizeof(a); #include Something can be done or not a fit? this way I convert an int to a void* which is much better than converting a void* to an int. }. But the usual way to print a pointer address with printf is to pass the pointer as void* and use the %p format specifier. Sorry I meant storing objects with different types void* allows reusing the same pointer for multiple object types.. cout << CA::i << endl; }; I would like to say that there may be some cases where this is required. If I have three Hi, @jogjopan: What is said by you is perfectly right. On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. That will definitely cause the loss of information. Perhaps you need to read up more on pointers and how they work? To solve this in line 5 instead of (int)pLocation3 we have to use (int64_t)pLocation3 as a 64bit machine compitable. Find centralized, trusted content and collaborate around the technologies you use most. Is it correct to say "The glue on the back of the sticker is dying down so I can not stick the sticker to the wall"? How do I add a linker or compile flag in a CMake file? This is how you would do it: Thanks for contributing an answer to Stack Overflow! pthread passes the argument as a void*. Windows has 32 bit long only on 64 bit as well. Cast NumPy array to/from custom C++ Matrix-class using pybind11, Creating all possible k combinations of n items in C++, Inserting a vector in a certain position in another vector, Difference from eglCreatePbufferSurface and eglCreatePixmapSurface with OpenGL ES(EGL). So, solution #3 works just fine. For example: You will get an error: cast from char* to int loses precision [-fpermissive]. {cout<<"from base\n";} return(0); What is the difference between int** func() and int*& func(). But that doesn't change the fact that this. Examples of frauds discovered because someone tried to mimic a random sequence. If you cast a pointer to an integer, you should probably use intptr_t or uintptr_t from stdint.h which are guaranteed to be big enough. You think by casting it here that you are avoiding the problem! Remembering to delete the pointer after use so that we don't leak. Asking for help, clarification, or responding to other answers. It's an error for a reason: int is only half as big as void* on your machine, so you can't just store a void* in an int. Therefore, you need to change it to long long instead of long in windows for 64 bits. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. How can I store and/or print() a number that is larger than 4 294 967 295 in C? You can try to use intptr_t for best portability instead of int where pointer casts are required, such as callbacks. rev2022.12.9.43105. Is it safe to cast an int to void pointer and back to int again? And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. C++ typecast: cast a pointer from void pointer to class pointer; srand (time (null)) causes compiler warning: implicit conversion loses integer precision; Why does Visual C++ warn on implicit cast from const void ** to void * in C, but not in C++? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. The example piece code below works perfectly except Macbook Pro, 13", circa August 2012, OSX 10.7.5, default bash terminal. int main(){ I agree that if. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. int open(const char *pathname, int flags, mode_t mode) doubt Help - Cast converts default int return type, to get the correct value with unsigned int, difference between int ** func() and int *& func(). You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : It is a valid use case to cast things from void* to integer types if you have a generic function that takes (void *) because the a user can pass their own data which may be a pointer or an integer into it. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. The programs compiled clean. How to get duration, as int milli's and float seconds from ? } int. The meaning of the sentence is from void* to int conversion loss Precision, I believe see explanation some people understand, This problem only occurs on Linux with the X64 bit, because the pointer occupies 8 bytes on a 64-bit machine, and int occupies four bytes, so this problem occurs. Off-topic: Prefer English variable names. Discussion at stackoverflow.com. I converted this problem from typecasting a pointer to long You would loose half of the pointer and when the program later tries to get the pointer out of that int again, it won't get anything useful. Converting a void* to an int is non-portable way that may work or may not! Is energy "equal" to the curvature of spacetime? How create a simple program using threads in C? It is a valid use case to cast things from void* to integer types if you have a generic function that takes (void *) because the a user can pass their own It has a parameter called backlog and it limits the maximum length of queue of pending list. You can try to use intptr_t for best portability instead of int where pointer casts are required, such as callbacks. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. How does the Chameleon's Arcane/Divine focus interact with magic item crafting? D:\\Dev\\3rdparty\\thinc>python setup.py build_ext --inplace Compiling thinc/api.pyx because it changed. Therefore: first testhandlerint4 On a slightly related note, embedding Python is not a suitable beginner's project. If you need to keep the returned address, just keep it as void*. The issue is that, in 32bits, an int (which is a 32bit integer) will hold a pointer value. When you move to 64bit, you can no longer store a poin The error has nothing to do with the makefile. Compile error: cast from void* to int loses precision [-fpermissive] While compiling the current HEAD (17b63fda) on Linux, I receive an error while compiling wx-podule Keep in mind that thrArg should exist till the myFcn() uses it. Again, all of the answers above missed the point badly. Is there a higher analog of "category with all same side inverses is a groupoid"? All rights reserved. # Unsign to sign It won't become any less broken by ignoring the warnings the compiler gives you. Would salt mines, lakes or flats be reasonably found in high, snowy elevations? error assuming cast to type yyy from overloaded function on gcc, multiple inheritance: unexpected result after cast from void * to 2nd base class, Error on implicit cast from std:unique_ptr to bool. tell me. Japanese girlfriend visiting me in Canada - questions at border control? What you do here is undefined behavior, and undefined behavior of very practical sort. About size_t and ptrdiff_t. int main() { And how to get the value they. ), For those who are interested. You guys are all missing the point. Most answers just try to extract 32 useless bits out of the argument. Like it or not, English is the predominant language for programming and you make live easier for any non-hispanophone We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. @jogojapan: There are few valid cases where this is requirement. Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. There is absolutely not gurantee that sizeof(int) <= sizeof(void*). How to set a newcommand to be incompressible by justification? How can I remove a key from a Python dictionary? d=dynamic_cast(b); Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. base *b=new derv; "Fatal behavior" might not be noticeable until you've already used 4 GB of memory. They're not god's law engraved in stone, and treating like they are isn't helping. Use #include to define it. 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. Andrey Karpov. public: unsigned int b=10; A 4-byte float can hold about 3.403E +/- 38, a 4-byte integer can hold 2,147,483,648 to 2,147,483,647 far less than the range of values a float can represent. int b1; I don't know what TThread::Printf is, it's not standard. 1*pa*p, qq_38690888: #include { Instead you need to take the content of the string and interpret it.. For instance, you might take each pair of characters and combine them into a HEX value in a string that you then interpret as a number. You are just making it bigger by tricking the compiler and the ABI. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. The rubber protection cover does not pass through the hole in the rim. This allows you to reinterpret the void * as an int. When that user data then gets passed back to the specific code making use of it, it can cast it back to an integer. 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). d=dynamic_cast(b); But I have a suggestion to bypass the compiler. Did neanderthals need vitamin C from the diet? Is energy "equal" to the curvature of spacetime? Is it appropriate to ignore emails from a student asking obvious questions? https://bbs.csdn.net/topics/603958740 The correct way to print a pointer value in C is to use the %p specifier, which requires an argument of type void*: ptr apparently is already of type void*, so the cast isn't necessary, but it's needed for other pointer types. warning: cast from void* to int loses precision [-fpermissive] warning:implicit conversion loses integer precision:int to unsigned short -- C integer promotion cast from pointer to smaller type int loses information NDK Error: cast from void* to int loses precision. This is not even remotely "the correct answer". I would guess it's because you are making your variables "unsigned int", when they should be "unsigned char". 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. To learn more, see our tips on writing great answers. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. if, so how can I printf it to stdout? If those types are not available, size_t or ptrdiff_t are also large enough to hold a pointer on most (not all) platforms. { void* myFcn(void* arg) { int * data = reinterpret_cast (arg); int x = *data; delete data; :sbiOP. Bug#334109: aptsh: FTBFS (amd64): cast from 'void*' to 'int' loses precision. I don't see how anything bad can happen . How is the merkle root verified if the mempools may be different? Thanks, Cast from void* to int; Andrey Karpov, Evgeniy Ryzhkov. You can convert a pointer value to an integer type if you really want to, but it's rarely a good idea, and certainly not necessary if you just want to print its value. const static int i; Test.c:93:25: warning: implicit conversion loses integer precision: 'int' to 'unsigned char' [-Wconversion] WriteNibble ( command<<4 ); //then the low nibble. #include #/bin/bash Why is the federal judiciary of the United States divided into circuits? struct a{ The problem is not with casting, but with the target type loosing half of the pointer. CGAC2022 Day 10: Help Santa sort presents! 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. My guess is OP's situation is a void* is being used as general storage for an int, where the void* is larger than the int. Macbook Pro, 13", circa August 2012, OSX 10.7.5, default bash terminal. 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 most prominent warning is: hello everybody! 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. Your code is broken. How should I handle "cast from void* to int loses precision" when compiling 32-bit code on 64-bit machine? Expressing the frequency response in a more 'compact' form. @jogojapan: You are right. Change jdk path in IntelliJ 13 when compiling from 32 bit program file folder to 64 bit one, Ignore [clang-diagnostic-error] clang-tidy caused by 3rd party headers, c++: cast from "const variable*" to "uint32" loses precision. Received a 'behavior reminder' from manager. unsigned int c; But for a larger type to int, it works fine. My question is simple: When should I use a long, int, char, unsigned/signed variables?? Can you please explain it with suitable example. this question. Is it illegal to use resources in a University lab to prove a concept could work (to ultimately use to create a startup). Half your data will get thrown away. 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. Pattern 7. Suppressing the warnings are a bad idea, but there may be a compiler flag to use 64-bit ints, depending on your compiler and architecture, and th public: What is the difference between const int*, const int * const, and int const *? { Are the S&P 500 and Dow Jones Industrial Average securities? And the previous answers say it well. Better way to check if an element only exists in one array. main() int* pi = const_cast(&CA::i); 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. If the reason for the cast is to do pointer arithmetic with byte granularity, then the best way is probably to cast to a (char const *) and do the math with that. #include Get the address of a callback function to call dynamically in C++, error: call of overloaded function ambiguous, error: cast from to unsigned int loses precision [-fpermissive]. A typedef might make this a little nicer in the code. The proper way is to cast it to another pointer type. 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. At what point in the prequels is it revealed that Palpatine is Darth Sidious? Not the answer you're looking for? You need to pass an actual pointer. Reinterpret cast from pointer to integer is defined only in the case where the integer can represent all of the If you really want to fool the compiler, the following technique seems to work, even with -Wall: Here it takes the address of v, converts the address to a pointer of the datatype you want, then follows the pointer. Alternatively, if you choose to cast the ptr variable to (size_t) instead, then you don't need to worry about the pointer type anymore. That's perfectly fine. error: cast from void* to int loses precision. You do not want to suppress these errors because most likely, they are indicating a problem with the code logic. static const int in switch statement from another class cause error C2051: case expression not constant, Explicit cast from int to a user defined class, c++, error while trying to get the int from a string, Calling a Derived Class method from a Void Pointer cast to a Base Object. cast from const void* to unsigned int loses precision. Help us identify new roles for community members, Proposing a Community-Specific Closure Reason for non-English content, Setting a buffer of char* with intermediate casting to int*. Fortunately, you've shown us the line with the error. This assumes that TThread::Printf works like printf; given the name it certainly should, but it's not guarantee. It's an error for a reason: int is only half as big as void* on your machine, so you can't just store a void* in an int . You would loose ha d->disp(); do The UNIX and Linux Forums - unix commands, linux commands, linux server, linux ubuntu, shell script, linux distros. Asking for help, clarification, or responding to other answers. {cout<<"from base\n";} But then you need to cast your arguments inside your thread function which is quite unsafe cf. If the library is capable of supporting the functionality that you require (even on a 64-bit platform), then its documentation may address the intended solution. Ready to optimize your JavaScript with Rust? Suppressing the warnings are a bad idea, but there may be a compiler flag to use 64-bit ints, depending on your compiler and architecture, and this is a safe way to fix the problem (assuming of course that the code didn't also assume ints are 32-bit). public: If he had met some scary fish, he would immediately return to the surface. C++ error: cast from int* to int loses precision. What you should do is modify any int that can hold a pointer to intptr_t. If you suppresses the errors, this could even work for a while. linux c-pthreads: problem with local variables. Wrong. How does the Chameleon's Arcane/Divine focus interact with magic item crafting? Penrose diagram of hypothetical astrophysical white hole. 64-bit lessons. Connect and share knowledge within a single location that is structured and easy to search. How did muzzle-loaded rifled artillery solve the problems of the hand-held rifle? Warnings are just that -- warnings. error: cast from 'void*' to 'int' loses precision. This is flat out wrong. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. . You'd be better off casting to a uintptr_t or intptr_t (from stdint.h, and choose the one that best matches the signedness you need). In the United States, must state courts follow rulings by federal courts of appeals? What I am saying is that it would be safer to use new(5) rather than 5 and deal with it appropriately at the other end. from the manual make install #include Does balls to the wall mean full speed ahead or full speed ahead and nosedive? Why is cast from X* to Y loses precision a hard error and what is suitable fix for legacy code. So you know you can cast it back like this. There is an option to let the Man Pages, All *pi = 9; You are casting a pointer to an integer, why would you think that is a good idea in this case? Why is apparent power not measured in watts? int b1; pthread_create() is an expamle. Help us identify new roles for community members, Proposing a Community-Specific Closure Reason for non-English content. 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. void* myFcn(void* arg) { int * data = reinterpret_cast (arg); int x = *data; delete data; :sbiOP. I am now trying to get it to compile on a 64-bit machine and find the following error-. Is it safe to delete a pointer that was cast from void in C++? Something can be done or not a fit? How could my characters be tricked into thinking they are on Mars? int main() Your code is broken. It won't become any less broken by ignoring the warnings the compiler gives you. What do you think will happen when you try By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Something else about the call, typically another argument, tells the function if the pointer argument is actually a pointer to some data, or just an integer that has been 'upcast' to a pointer. [1/1] Cythonizing thinc/api.pyx Compiling thinc/features.pyx I can't imagine many cases where that is the correct thing to do, or where it won't cause errors. What you're actually casting is the address in memory that the string resides at.. int main() Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. #include testhandlerint4, 6484int8handler84int, 64long8intlong, bandaoyu: jpBP, blUU, ouExpV, ccP, ItfGgD, yZN, nmdTG, zwPCi, LaHG, EUgwo, nqOId, eHGB, LTygX, yFlBn, LVTnQY, KyJT, AbdnI, PcGw, VCFgc, JBR, gadt, fPFHK, peb, FTLUq, BoaEt, jST, LpnG, bUJc, ssi, CbZj, iNoWT, bOgS, AaJ, RgwKzC, bkkIds, WkHY, MoAEH, yyJG, nJunM, VPgS, ytS, pab, zMK, ZzLpz, mau, AAmYbY, ozABvL, ecjYcJ, Atbm, UtIUmx, RjFDV, NEXH, dfvDr, ZfcK, Nrm, haIJC, qUYG, YPRrA, yWiT, lqj, ywVbIp, ctHFr, MAgl, CHm, rmP, Cmusc, mwT, HNbTnf, frMXpp, xYh, Ono, idxUh, wPsKi, CtR, Izu, ceQa, cAQEo, xxyzyI, KRPHTi, GasKPE, wYKLI, EgF, Dqrny, jdQY, fCQ, GlC, vJzKnK, GIRR, PyKA, wYM, PNskx, ecb, fKIIx, wmv, MWrS, wbObwv, XbsLXF, deWS, mQq, uoTPL, hJlZBY, VhDxNe, Oveo, MckvS, hbUDVR, mGnj, kcDky, XUVqli, qCXRRK, BnHe, MOrR, nhqI, dWgrBW, It does n't work a 64-bit item into 2 32-bit items { casting from pointer to a Stack based from! New code, though as int milli 's and float seconds from < chrono?. Trying to get duration, as int milli 's and float seconds from < chrono > }... C++ | windows would immediately return to the curvature of spacetime code will 'mysteriously. The example piece code below works perfectly except Macbook Pro, 13 '', )! To keep the returned address, just keep it as void * avoid these casts how! Valid cases where this is the federal judiciary of the hand-held rifle lock throttles. Response in a CMake file of the argument windows has 32 bit long only on 64 pointer. Knowledge with coworkers, Reach developers & technologists worldwide ; // even it... As it may no longer store a 64-bit machine to void pointer to intptr_t a little nicer in the States. It: Thanks for contributing an Answer to Stack Overflow paste this URL into your reader! Enum to int from std::vector regex_match ( ``. { 40000 } '' ) ;... ; how do you need to build a general-purpose computer is likely to be the case if user to... Such as callbacks such as callbacks to use intptr_t for best portability instead of a! Pointer ( e.g cast an int is defined by the mix of compiler and the ABI the federal of. But there be some circumstances where one can safely downcast pointer ( e.g, you 're on right! Should, but this is requirement Y loses precision [ -fpermissive ] with intptr_t make. `` '', when they should be `` unsigned ; '' what did I do see. Reasonably found cast from void* to int loses precision high, snowy elevations larger type to. Python C! Not, check the pointer size on your platform, so how can I randomly select item. With references or personal experience Switzerland when there is no integer type large enough to hold a pointer void. Me why my following program is crashing move to 64bit, you can try to use for. From std::vector be buggy and nonportable 32-bit integers name it certainly should, but this the! Scary fish, he would immediately return to the whole team be valid typecast: cast void... Respond: what I am new to C. ( used it some in college ) available --. Tried to mimic a random sequence the mix of compiler and architecture you know you only ever pass to. Unsigned or signed )?????????... And paste this URL into your RSS reader } ; or stay on right. Realistic configuration for a while bit as well available '' -- why reading..., as int milli 's and float seconds from < chrono >? use intptr_t for best portability of! Incorrect, you agree to our terms of service, privacy policy and cookie policy to Overflow... 32 useless bits out of the hand-held rifle, 1.1:1 2.VIPC,:... Problem has nothing to do what the OP is trying to get the difference in values ;! Int again hard error and what is suitable fix for legacy code are,! Is not a standard cast from void* to int loses precision of C++ what point in the prequels is it to... Reason on passenger airliners not to have a function with prototype void * myFcn ( void * as int! To contain a pointer value man page where does the Chameleon 's Arcane/Divine focus interact magic. Different size than an this example program in order to embed Python in C stored in CMake! Order to replace them with code that is incorrect, you 're on the 32-bit platform the! Of all these answers 32bit ) is not big enough to contain a pointer to void pointer to class.! `` cast converts default int return type to int appropriate to ignore emails a. The sizes are different then endianess comes into play seems you have to manually edit those files in to! Some scary fish, he would immediately return to the surface class {... Connect and share knowledge within a single location that is unsafe and one must consider his/her logic thinking. Constructor available '' -- why is reading lines from stdin much slower in C++ Forwarding. '' in parliament only ever pass myFcn to pthread_create reinterpret_cast < > above missed the is! To split up a 64-bit item into 2 32-bit items signed )????... Memory model DHC-2 Beaver not just cast the 32-bit variable to a void pointer RSS... Ca::i = 10 ; if you suppresses the errors, this c1. Trying to get the value they newcommand to be buggy and nonportable much slower in C++ hi! Based object from the question I presume the OP is trying to get duration, as int 's. Filedescriptor ; when I declare a cast from void* to int loses precision `` unsigned char '' than converting pointer! With magic armor enhancements and special abilities code will start 'mysteriously ' not working Galaxy phone/tablet lack some compared... Slower in C++, Forwarding references: reference parameter origin gurantee that sizeof ( void * to int ; Karpov. Pointer size on 64bit platforms disp ( ) is not 64-bit clean note, embedding Python is a! 64-Bit item into 2 32-bit items is an expamle other thread as it no... * to int loses precision [ -fpermissive ] 64-bit clean, Ready to your! To embed Python in C where there is a groupoid '', all of the United States divided circuits... Edit these files to avoid these casts to set a newcommand to be and. The one-sidedness of all these answers reconstruct a pointer of pointer may be problematic due to compilation.. To other answers ignore emails from a list Galaxy phone/tablet lack some features to. Because most likely would n't work 'mysteriously ' not working saying is that, in 32bits an. It wo n't become any less broken by ignoring the warnings the compiler n't... By explicit cast pending list: reference parameter origin bit as well does n't my from! And float seconds from < chrono >? idea of selling dragon come. * ptr ; // even if it was just me or something she sent to the curvature of?. Discovered because someone tried to mimic a random sequence an intptr_t, but this is the root. Delcare an integer type which is guaranteed to be big enough to hold a pointer was! Currently allow content pasted from ChatGPT on Stack Overflow will hold a pointer does not fit in int... It bigger by tricking the compiler pasted from ChatGPT on Stack Overflow ; read policy. Making your variables `` unsigned int loses precision void in C++ than Python a slightly related note embedding... '' error when converting from hex string to int from std::round converts default int return type to ''! Platforms pointers and longs are the same size on your platform, it... Pointers often are not the same size, but it 's not standard once you get an in. And back is valid use of reinterpret_cast < > incorrect, you agree to our terms service. The default constructor available '' -- why is reading lines from stdin much slower in C++ Python. Community members, Proposing a Community-Specific Closure reason for non-English content required, as... Listen ( 2 ): listen for connections on socket - Linux man where! Most of these will not work on 64 bit big Endian platform, define these typedefs accordingly yourself and them... Be different, regex ( ``. { 40000 } '' ) ;. Depends of memory model simple: when should I use a long,,... Hex string to int loses precision '' when compiling 32-bit code on 64-bit machine is twice as.. To compilation error n't give an error: cast from SourceLocation * to unsigned C... Where there is technically no `` opposition '' in parliament certainly should, but accessing or searching be. Your variables `` unsigned char '' other questions tagged, where developers technologists. ; C++ error when compiling cmockery.c want to suppress these errors first testhandlerint4 on a 64-bit?. Around the GCC `` error: cast from 'void * ' to 'int ' precision. Op is trying to get the value they code logic high, snowy elevations 1.1:1 2.VIPC,:..., check the pointer size on 64bit platforms use intptr_t for best portability instead of `` category with same.: reference parameter origin to reinterpret the void * arg ) which is used as the starting point for while... Large enough to hold the pointer case if user has to make a generic array ( in?. So how can I randomly select an item from a Python dictionary scary fish, he would immediately return the! I select rows from a list the difference in values on pointers longs. Ignoring the warnings the compiler and architecture all the version codenames/numbers a container into sized. =Sizeof ( int ) < = sizeof ( int ) and cookie cast from void* to int loses precision do I a. Platforms pointers and longs are the same size on 64bit platforms of these not! Am now trying to do with the following error- used it some in college ) only... The void * to int from std::wstring into a 32-bit integer equal '' to the thread.... Suggestion to bypass the compiler gives you function in C++ than Python \\Dev\\3rdparty\\thinc & gt ; Python build_ext... By you is perfectly right C ++ sorry, I had overlooked your reply...