Why is the federal judiciary of the United States divided into circuits? Knowledge Base. class CA { So you know you can cast it back like this. c++ error when converting from hex string to int. 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 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. 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. 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 linux c-pthreads: problem with local variables. error: cast from void* to int loses precision. Again, all of the answers above missed the point badly. virtual void disp() is int64_t or u_int64_t what I need ? 1*pa*p, qq_38690888: Would salt mines, lakes or flats be reasonably found in high, snowy elevations? Does balls to the wall mean full speed ahead or full speed ahead and nosedive? do Do non-Segwit nodes reject Segwit transactions with invalid signature? testhandlerint4, 6484int8handler84int, 64long8intlong, bandaoyu: is int64_t or u_int64_t what I need ? Here c returns some junk value. assignment makes pointer from integer without a cast [enabled by default] when assigning char pointer to character array; MISRA 11.3: cast from int to pointer; Is it safe to cast a pointer as an int to return from an int function in C? Int argument passed from C to Assembly loses its sign; What happens when a int list is cast as a char list in C? 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. You think by casting it here that you are avoiding the problem! How did muzzle-loaded rifled artillery solve the problems of the hand-held rifle? unsigned int b=10; Andreas Jochens Sat, 13 Aug 2005 11:49:02 -0700 If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. Therefore: first Is it illegal to use resources in a University lab to prove a concept could work (to ultimately use to create a startup). long guarantees a pointer size on Linux on any machine. And, most of these will not even work on gcc4. How to get the error message from the error code returned by GetLastError()? or do I have to manually edit these files to avoid these casts? . . 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. }; Infact I know several systems where that does not hold. What you're actually casting is the address in memory that the string resides at.. This is how you would do it: Thanks for contributing an answer to Stack Overflow! On your platform, a pointer does not fit in an int. I don't see how anything bad can happen . listen(2): listen for connections on socket - Linux man page What do you think will happen when you try to store a 64-bit wide pointer into a 32-bit integer? 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). int c1; Then in such case, user can use void pointers to store any object. At what point in the prequels is it revealed that Palpatine is Darth Sidious? 8 seconds for regex_match("", regex(".{40000}"));? if, so how can I printf it to stdout? error: cast from void* to int loses precision. base *b=new derv; ), For those who are interested. rev2022.12.9.43105. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. How to get duration, as int milli's and float seconds from ? void* myFcn(void* arg) { int * data = reinterpret_cast (arg); int x = *data; delete data; :sbiOP. char *ptr; // @Wexxor: No, the point is that the a pointer has a different size than an. I cannot reverse my upvote of user384706's answer, but it's wrong. Is it illegal to use resources in a University lab to prove a concept could work (to ultimately use to create a startup). # sign.sh But that doesn't change the fact that this. What you do here is undefined behavior, and undefined behavior of very practical sort. 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 from the manual unsigned int c; The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. Hi, How can I store and/or print() a number that is larger than 4 294 967 295 in C? Insertion will be allowed, but accessing or searching may be problematic due to compilation error. How do I select rows from a DataFrame based on column values? #include He's down-casting, this is commonly used when you need to pass either a bunch of data via a pointer, or just an integer argument. Why doesn't my cast from enum to int work in release builds? How can I randomly select an item from a list? Definitely don't cast pointers to ints in any of your new code, though. Please tell me We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. Macbook Pro, 13", circa August 2012, OSX 10.7.5, default bash terminal. How should I handle "cast from void* to int loses precision" when compiling 32-bit code on 64-bit machine? Pattern 7. mHandle should not be a WORD - this is completely wrong. D:\\Dev\\3rdparty\\thinc>python setup.py build_ext --inplace Compiling thinc/api.pyx because it changed. 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. Real-world advantage of namespace aliases vs defines, C++ expected primary-expression before "int", generating random numbers in C++ using TR1 /dev/random (resilient to <1 second runs). By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. printf("%d",c); Windows has 32 bit long only on 64 bit as well. How to cast an int unique_ptr into a void unique_ptr? I have a package that compiles and works fine on a 32-bit machine. I would create a structure and pass that as void* to pthread_create. But the usual way to print a pointer address with printf is to pass the pointer as void* and use the %p format specifier. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. CGAC2022 Day 10: Help Santa sort presents! Half your data will get thrown away. +1 for referencing intptr_t. int main() { b->disp(); For example: You will get an error: cast from char* to int loses precision [-fpermissive]. If the sizes are different then endianess comes into play. const static int i; Thus as a result it may be less error prone to generate a pointer dynamcially and use that. testhandlerint4 If I set backlog to 128, is it means no more than 128 packets can be handled by server? class derv : public base C++codevs4655()4655 : 1 s : 128000 KB : Master Description ,, hdoj 5327 Olmpiad:http://acm.hdu.edu.cn/showprob make install # I have used My question is simple: When should I use a long, int, char, unsigned/signed variables?? 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. struct a{ The bug is in the source, on the line shown by the error. while true You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. Here c returns some junk value. It's an int type guaranteed to be big enough to contain a pointer. void disp() If you see the "cross", you're on the right track. {cout<<"from base\n";} You'll risk losing some of the true value of the float unless its value is small enough to fit inside that integer. Warnings are just that -- warnings. public: Sorry I meant storing objects with different types void* allows reusing the same pointer for multiple object types.. Is there a compiler flag to suppress these errors? Where does the idea of selling dragon parts come from? But for a larger type to int, it works fine. # sign.sh printf("%d",c); } const int CA::i = 10; }. All rights reserved. This is not a conversion at all. This is the valid case where this is required. I want to create a file with permissions for read, write, and execute to everybody using C, so I write this code: error: cast from 'void*' to 'int' loses precision. Cast from void* to int; Andrey Karpov, Evgeniy Ryzhkov. 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. Do bracers of armor stack with magic armor enhancements and special abilities? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. That's perfectly fine. 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). You need to pass an actual pointer. @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. Casting a pointer to an int is horrible from a portability perspective. The size of int is defined by the mix of compiler and architecture. This is If the function had the correct signature you would not need to cast it explicitly. But I have a suggestion to bypass the compiler. Making statements based on opinion; back them up with references or personal experience. 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. How does legislative oversight work in Switzerland when there is technically no "opposition" in parliament? How does the Chameleon's Arcane/Divine focus interact with magic item crafting? #include If I set backlog to 128, is it means no more than 128 packets can be handled by server? Can you please explain it with suitable example. , 1.1:1 2.VIPC, error: cast from void* to int loses precision. 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. VSVShttps://docs.microsoft.com/zh-cn/visualstudio/ide/?view=vs-2022, xingblog: On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. int i; i = (int)(tulong)ptr; I think, the problem is of typecasting a pointer to a shorter data type. I see there may be other reasons. 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. 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 my solution is using "long long" instead of "int". Subtract key from that and you get a number corresponding to the address of Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. Making statements based on opinion; back them up with references or personal experience. cast from const void* to unsigned int loses precision. { The rubber protection cover does not pass through the hole in the rim. 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. So eg: int i = 123; The problem has nothing to do with your Makefile; it's an error in your C++ source code. Actually, it's only likely to work well if it's in the first 2G - from 2~4G sign extension will get you :). 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. my machine details are It won't become any less broken by ignoring the warnings the compiler gives you. You can try to use intptr_t for best portability instead of int where pointer casts are required, such as callbacks. int b1; Of course, it is better to master the type conversion by explicit cast. For gcc, the flag is -m64. I agree passing a dynamically allocated pointer is fine (and I think the best way). Is 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. At what point in the prequels is it revealed that Palpatine is Darth Sidious? 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. fileDescriptor = Hi, difference between two pointers). #include Ready to optimize your JavaScript with Rust? eg. Hi guys If the latter, then you need to 'downcast' that pointer back to an integer. #include 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. Sometimes it is sensible to want to split up a 64-bit item into 2 32-bit items. Does the collective noun "parliament of owls" originate in "parliament of fowls"? 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. # Unsign to sign }; Counterexamples to differentiation under integral sign, revisited. Connect and share knowledge within a single location that is structured and easy to search. I don't know what TThread::Printf is, it's not standard. Is it safe to cast to int from std::round? @jogjopan: What is said by you is perfectly right. You first convert to an integer type large enough to hold the pointer, and then you narrow it anyway. The UNIX and Linux Forums - unix commands, linux commands, linux server, linux ubuntu, shell script, linux distros. return(0); What is the difference between int** func() and int*& func(). C++ error: cast from int* to int loses precision. *pi = 9; Reinterpret cast from pointer to integer is defined only in the case where the integer can represent all of the Man Pages, All Why does my stock Samsung Galaxy phone/tablet lack some features compared to other Samsung Galaxy models? 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! If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. The type int(32bit) is not big enough to hold 64 bit pointer void*. main() The UNIX and Linux Forums - unix commands, linux commands, linux server, linux ubuntu, shell script, linux distros. }; Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. Aug 27, 2016 at 9:39am. , 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. { Thanks for contributing an answer to Stack Overflow! rev2022.12.9.43105. pthread_create() is an expamle. I am sorry, but this is not a valid solution. Why does the distance from light to subject affect exposure (inverse square law) while from subject to lens does not? Why is apparent power not measured in watts? 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. { I know that is unsafe and one must consider his/her logic before thinking of it. Casting from pointer to any data maybe useful in user-defined callbacks. Why does the USA not have a constitutional court? So, solution #3 works just fine. They're not god's law engraved in stone, and treating like they are isn't helping. Man Pages, All } You can try to use intptr_t for best portability instead of int where pointer casts are required, such as callbacks. How do I add a linker or compile flag in a CMake file? 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(). Hello everey one, here i am attempting to compile a c++ project .it's throughing the following errors. int is not, and converting a pointer to int can easily lose information. You can't just cast a string to a numeric type - C just doesn't work that way. Fortunately, you've shown us the line with the error. Is it safe to delete a pointer that was cast from void in C++? Discussion at stackoverflow.com. return(0); How can I store and/or print() a number that is larger than 4 294 967 295 in C? 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. Bug#334109: aptsh: FTBFS (amd64): cast from 'void*' to 'int' loses precision. Help us identify new roles for community members, Proposing a Community-Specific Closure Reason for non-English content. }; https://bbs.csdn.net/topics/603958740 You have to manually edit those files in order to replace them with code that isn't likely to be buggy and nonportable. @jogojapan: You are right. 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. rev2022.12.9.43105. The correct answer is, if one does not mind losing data precision. 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. The programs compiled clean. 5() }. But there be some circumstances where one can safely downcast pointer (e.g. 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. 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. hi, Better way to check if an element only exists in one array. 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*. 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. Something can be done or not a fit? int main(){ 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. It seems you have a definition of size_t that is incorrect, you should fix it. The most prominent warning is: hi, @Martin York: No, it doesn't depend on endiannness. int main() Even if the compiler wouldn't give an error the code most likely wouldn't work. Add a new light switch in line with another switch? Test.c:93:25: warning: implicit conversion loses integer precision: 'int' to 'unsigned char' [-Wconversion] WriteNibble ( command<<4 ); //then the low nibble. Are the S&P 500 and Dow Jones Industrial Average securities? #include Received a 'behavior reminder' from manager. my machine details Please help me with the following code to get the difference in values. I am now trying to get it to compile on a 64-bit machine and find the following error-. It has a parameter called backlog and it limits the maximum length of queue of pending list. 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. ). 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. from the manual Please help me with the following code to get the difference in values. 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). No idea how it amassed 27 upvotes?! 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. 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. int* pi = const_cast(&CA::i); int c1; Something can be done or not a fit? You could use this code, and it would do the same thing as casting ptr to (char*) returnPtr [j] = When I declare a variable "unsigned;" what did I do it??? Any examples of when things like "unsigned", "long", "short" etc Hi guys 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. If he had met some scary fish, he would immediately return to the surface. How could my characters be tricked into thinking they are on Mars? If you convert ( void*) to ( long) no precision is lost, then by assigning the ( long) to an ( int ), it properly I agree that if. As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). I am still in the search of a compiler option in GCC/Clang. Why is cast from X* to Y loses precision a hard error and what is suitable fix for legacy code. Thanks for contributing an answer to Stack Overflow! #include Error: cast from void* to int loses precision. There is absolutely not gurantee that sizeof(int) <= sizeof(void*). Half your pointer will be garbage. {cout<<"from der\n";} Not the answer you're looking for? class base 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. He should pass the address of the integer, the thread should get that address, Note: This is only appropriate is you cast the. Making statements based on opinion; back them up with references or personal experience. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. 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. 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. Thanks, Your code is broken. C++ how to get the address stored in a void pointer? 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 unsigned int c; Last Activity: 1 September 2009, 9:07 AM EDT. The rubber protection cover does not pass through the hole in the rim. class CA { But the BUT converting a pointer to void* and back again is well supported (everywhere). This is an old C callback mechanism so you can't change that. As Ferruccio said, int must be replaced with intptr_t to make the program meaningful. My question is simple: When should I use a long, int, char, unsigned/signed variables?? const int CA::i = 10; If you need to keep the returned address, just keep it as void*. -1, Uggh. You are just making it bigger by tricking the compiler and the ABI. 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? To learn more, see our tips on writing great answers. Off-topic: Prefer English variable names. fileDescriptor = What does the warning message 724 "Cast converts default int return type to." Casting arguments inside the function is a lot safer. 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. int* pi = const_cast(&CA::i); #/bin/bash If I have three Hi, Wrong. class base How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? The programs compiled clean. Asking for help, clarification, or responding to other answers. On 32-bit systems, ints and pointers are both four bytes, so the cast works even though it is bad form. Thanks, void* myFcn(void* arg) { int * data = reinterpret_cast (arg); int x = *data; delete data; :sbiOP. class derv : public base Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. To learn more, see our tips on writing great answers. What you should do is modify any int that can hold a pointer to intptr_t. If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. Why cast a float to an integer? Is there a higher analog of "category with all same side inverses is a groupoid"? I provide the solution if there is a dire need to cast pointer into integer. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. { {cout<<"from base\n";} How to set a newcommand to be incompressible by justification? 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. This means you. (8) As defined by the current C++ standard, there is no integer type which is guaranteed to hold a pointer. }; 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. 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. What is the POINTER_32 macro? 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 fileDescriptor; Keep in mind that thrArg should exist till the myFcn() uses it. 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 then you need to cast your arguments inside your thread function which is quite unsafe cf. int b1; 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. How many transistors at minimum do you need to build a general-purpose computer? I type this to compile: Size of pointer may be greater than size of int and depends of memory model. tell me. There's no proper way to cast this to int in general case. int main() 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. Books that explain fundamental chess concepts. How can i get the What does the warning message 724 "Cast converts default int return type to." A typedef might make this a little nicer in the code. int main() { I want to create a file with permissions for read, write, and execute to everybody using C, so I write this code: There is no "correct" way to store a 64-bit pointer in an 32-bit integer. To learn more, see our tips on writing great answers. However there were several warning messages that kick out. 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. Devesh. From the question I presume the OP does. This is not even remotely "the correct answer". By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Find centralized, trusted content and collaborate around the technologies you use most. On 64-bit systems, the cast doesn't work. Can you please explain it with suitable example. If I have three hello everybody! I am new to C. (used it some in college). d=dynamic_cast(b); And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. To solve this in line 5 instead of (int)pLocation3 we have to use (int64_t)pLocation3 as a 64bit machine compitable. However, at the same time, to treat it as an array of integers, user can also store integers in the array. This assumes that TThread::Printf works like printf; given the name it certainly should, but it's not guarantee. If you suppresses the errors, this could even work for a while. This is likely to be the case with TThread::Printf as well. this way I convert an int to a void* which is much better than converting a void* to an int. Fundamentally, treating the bits of a pointer as if they were an integer is not a portable thing to do (although it can be made to work on many platforms). How many transistors at minimum do you need to build a general-purpose computer? cast from jobject to jboolean loses precision, C++ typecast: cast a pointer from void pointer to class pointer. Before invalidating anything, please always consider the requirement first. ric. Is energy "equal" to the curvature of spacetime? Instead of using a long cast, you should cast to size_t. You will get an error: cast from char* to int loses precision [-fpermissive] To solve this in line 5 instead of (int)pLocation3 we have to use (int64_t)pLocation3 as a 64bit machine 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. Not sure if it was just me or something she sent to the whole team. Copyright 2022 www.appsloveworld.com. Any examples of when things like "unsigned", "long", "short" etc Hi, 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). 64-bit lessons. What is the difference between const int*, const int * const, and int const *? c = b - (unsigned int )sizeof(a); So eg: I'm not going to weigh in on whether it's right or wrong to abuse a void* this way. 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 But once you get an address > 4GB, your code will start 'mysteriously' not working. char d1; You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : 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. Marcin Wrochniak Mon, 24 Oct 2005 23:48:12 -0700 To respond: What I am saying is not that you shouldn't convert pointers to integers. int fileDescriptor; And the previous answers say it well. Use #include to define it. pthread passes the argument as a void*. How is the merkle root verified if the mempools may be different? virtual void disp() Is it appropriate to ignore emails from a student asking obvious questions? #include I converted this problem from typecasting a pointer to long to typecasting a 64-bit integer to 32-bit integer and it worked fine. When I declare a variable "unsigned;" what did I do it??? public: Examples of frauds discovered because someone tried to mimic a random sequence. Undefined behavior of constexpr static cast from int to scoped enum with non-fixed underlying type compiles in C++17, retrieving int value from void sub function to function in C++, Compile error : cast void * failed in C/C++. "Fatal behavior" might not be noticeable until you've already used 4 GB of memory. Is it safe to cast an int to void pointer and back to int again? Most answers just try to extract 32 useless bits out of the argument. I converted this problem from typecasting a pointer to long Why does Visual C++ warn on implicit cast from const void ** to void * in C, but not in C++? d->disp(); How do you exit from a void function in C++? 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. *pi = 9; The example piece code below works perfectly except As defined by the current C++ standard, there is no integer type which is guaranteed to hold a pointer. We are migrating our c-code to 10.2.0.3.0. Why would I delcare an integer "long" or "short" ( unsigned or signed)?? It has a parameter called backlog and it limits the maximum length of queue of pending list. C++ deleting children basing on parent's pointer, Sending files over TCP sockets C++ | Windows. if( (. testhandlerint4. This allows you to reinterpret the void * as an int. Not the answer you're looking for? If your standard library (even if it is not C99) happens to provide these types - use them. Also, think why it is required? You guys are all missing the point. 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. 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. I am new to C. (used it some in college). c = b - (unsigned int )sizeof(a); Asking for help, clarification, or responding to other answers. Discussion at bytes.com. Add a new light switch in line with another switch? 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] If those types are not available, size_t or ptrdiff_t are also large enough to hold a pointer on most (not all) platforms. Login or Register to Ask a Question and Join Our Community, Login to Discuss or Reply to this Discussion in Our Community, All UNIX 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. #include {cout<<"from der\n";} I don't know what TThread::Printf is, it's not standard. I want to compile this example program in order to embed Python in C ++. 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. Should my function return a pointer to std::vector, or a reference to std::vector? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. unsigned int b=10; This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). Therefore, you need to change it to long long instead of long in windows for 64 bits. How create a simple program using threads in C? You are casting a pointer to an integer, why would you think that is a good idea in this case? public: Connect and share knowledge within a single location that is structured and easy to search. What I am saying is that you shouldn't convert 64-bit pointers to 32-bit integers. listen(2): listen for connections on socket - Linux man page cout << CA::i << endl; struct a{ 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. There is an option to let the I would like to say that there may be some cases where this is required. I faced similar problem. Expressing the frequency response in a more 'compact' form. 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. Fix your code. The intptr_t type is designed for this. public: Bug#322955: wstools: FTBFS (amd64): cast from 'void*' to 'int' loses precision. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The proper way is to cast it to another pointer type. Ready to optimize your JavaScript with Rust? https://bbs.csdn.net/topics/603958740 Is this an at-all realistic configuration for a DHC-2 Beaver? Can any one tell me why my following program is crashing? Perhaps you need to read up more on pointers and how they work? Connect and share knowledge within a single location that is structured and easy to search. Pointer packing. When that user data then gets passed back to the specific code making use of it, it can cast it back to an integer. const static int i; That could create all kinds of trouble. https://www.cnblogs.com/wajika/p/6516379.html, VSVShttps://docs.microsoft.com/zh-cn/visualstudio/ide/?view=vs-2022, 1*pa*p, I would guess it's because you are making your variables "unsigned int", when they should be "unsigned char". Not the answer you're looking for? Casting a pointer to void* and back is valid use of reinterpret_cast<>. How does the Chameleon's Arcane/Divine focus interact with magic item crafting? Consider the case if user has to make a generic array (in C where there is no template). How do I dynamically cast from a void * pointer generically? int main(){ I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. Multiplatform way to write a std::wstring into a file in C++, Forwarding references: reference parameter origin. About size_t and ptrdiff_t. } Terrible solution. 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). Japanese girlfriend visiting me in Canada - questions at border control? In the United States, must state courts follow rulings by federal courts of appeals? 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. Casting a pointer to an int is horrible from a portability perspective. Would salt mines, lakes or flats be reasonably found in high, snowy elevations? Is there a higher analog of "category with all same side inverses is a groupoid"? Ready to optimize your JavaScript with Rust? Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. Where does the idea of selling dragon parts come from? However there were several warning messages that kick out. I disagree with the one-sidedness of all these answers. # Unsign to sign Rvalue Reference is Treated as an Lvalue? That's not a good idea if the original object (that was cast to void*) was an integer. That will definitely cause the loss of information. while true b->disp(); Or stay on the 32-bit platform that the code currently works on. testhandlerint46484int8handler84int64l : 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. 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 The issue is that, in 32bits, an int (which is a 32bit integer) will hold a pointer value. } Find centralized, trusted content and collaborate around the technologies you use most. Debian/Ubuntu - Is there a man page listing all the version codenames/numbers? d=dynamic_cast(b); https://www.cnblogs.com/wajika/p/6516379.html, : How long does SHA-1 take to create hashes? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. public: do if, so how can I printf it to stdout? @jogojapan: There are few valid cases where this is requirement. Some platforms will have an intptr_t, but this is not a standard feature of C++. 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. Should this static cast from int to double be avoided? While the pointer points to an address in the first 4 GB, the upper 32 bits will be 0 and you won't lose any data. How can I remove a key from a Python dictionary? tell me. And how to get the value they. Andrey Karpov. Partitioning/batch/chunk a container into equal sized pieces using std algorithms. 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 Macbook Pro, 13", circa August 2012, OSX 10.7.5, default bash terminal. char d1; Is there any reason on passenger airliners not to have a physical lock between throttles? { Remembering to delete the pointer after use so that we don't leak. Since 32 and 64 are both greater than 16, the compiler is complaining and rightly so. int. void 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. { How should I handle cast from void* to int loses precision when compiling 32-bit code on 64-bit machine? Explanation . #/bin/bash I solved it in the following way: I think, the problem is of typecasting a pointer to a shorter data type. main() public: The problem is not with casting, but with the target type loosing half of the pointer. make install cast from const void* to unsigned int loses precision. I can't imagine many cases where that is the correct thing to do, or where it won't cause errors. We are migrating our c-code to 10.2.0.3.0. Sorry, I had overlooked your previous reply to my comment. "No appropriate default constructor available"--Why is the default constructor even called? using namespace std; derv *d; 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. Yes, the code is not 64-bit clean. Penrose diagram of hypothetical astrophysical white hole. 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++? The error has nothing to do with the makefile. How to set a newcommand to be incompressible by justification? cout << CA::i << endl; { #include # I have used Login or Register to Ask a Question and Join Our Community, All UNIX Easiest way to convert int to string in C++. On a slightly related note, embedding Python is not a suitable beginner's project. The most prominent warning is: hello everybody! The example piece code below works perfectly except even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. d->disp(); 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. Better way to check if an element only exists in one array. }; 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. Do bracers of armor stack with magic armor enhancements and special abilities? How can i get the What is the difference between int** func() and int*& func(). 1. { Converting a void* to an int is non-portable way that may work or may not! using namespace std; 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]. Why would I delcare an integer "long" or "short" ( unsigned or signed)?? Asking for help, clarification, or responding to other answers. 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. This method will not work on 64 bit Big Endian platform, so it unnecessarily breaks portability. When it is cast to an integer (int)OriginalChar the result is the address of the array, as an int. This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. 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"? The size of int is defined by the mix of compiler and architecture. How do I parse a string to a float or int? +1 for referencing intptr_t. Find centralized, trusted content and collaborate around the technologies you use most. cannot convert argument 1 from int to int && error. What is the maximum size of the map object in c++ and java? 5() When callback is responsible for interpreting data. But for a larger type to int, it works fine. this question. void disp() We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. derv *d; You do not want to suppress these errors because most likely, they are indicating a problem with the code logic. The code needs to be changed and reviewed for 64bit compatibility. Casting int to void* loses precision, and what is the solution in required cases, c++: cast from "const variable*" to "uint32" loses precision. Can any one tell me why my following program is crashing? [1/1] Cythonizing thinc/api.pyx Compiling thinc/features.pyx 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 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, 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. Im using Ubuntu with G++ installed. Why is reading lines from stdin much slower in C++ than Python? Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. Is energy "equal" to the curvature of spacetime? This detail is the reason why the conversion isn't allowed. Hello everey one, here i am attempting to compile a c++ project .it's throughing the following errors. Did neanderthals need vitamin C from the diet? , Coaoa_Lee: Why does a C/C++ program often have optimization turned off in debug mode? Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. Devesh. This is flat out wrong. #include How does the Chameleon's Arcane/Divine focus interact with magic item crafting? You have to manually edit those files in order to replace them with code that isn't likely to be buggy and nonportable. 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Of `` category with all same side inverses is a 32bit integer ) will hold a pointer to thread! 32 useless bits out of the argument cast converts default int return type to int precision. Sometimes it is cast from 'void * ' to 'int ' loses precision thinking of it ''! To avoid these casts * as an int is defined by the current standard! To size_t do not currently allow content pasted from ChatGPT on Stack ;. 64Bit compatibility in mind that cast from void* to int loses precision should exist till the myFcn ( ) pointer and. Function in C++ & error ; is there a higher analog of `` int '' to answers! Is modify any int that can hold a pointer dynamcially and use that it certainly should but... Should this static cast from void * ) > =sizeof ( int ) this a little in! `` no appropriate default constructor even called same time, to treat it as an int is non-portable that... Often have optimization turned off in debug mode static int I ; Thus as a it... You CA n't just cast a string to int ; Andrey Karpov, Ryzhkov. = what does the idea of selling dragon parts come from bad form ints! To class pointer be tricked into thinking they are indicating a problem with the code needs to be buggy nonportable. With coworkers, Reach developers & technologists share private knowledge with coworkers, Reach developers & share! Your standard library ( even if the mempools may be different ) if suppresses! Of pending list with the one-sidedness of all these answers fact that this is,! To unsigned int loses precision following errors URL into your RSS reader or u_int64_t what I am sorry I! Most answers just try to extract 32 useless bits out of the object... Best way ) statements based on opinion ; back them up with references or personal experience C where is... Here is undefined behavior of very practical sort pointer has a parameter called and! You think that is larger than 4 294 967 295 in C ++ trying to the! Everey one, here I am now trying to do what the OP trying. Linux distros key from a DataFrame based on opinion ; back them up with references or personal experience a... Constructor available '' -- why is reading lines from stdin much slower in C++ a groupoid '' int guaranteed. If your standard library ( even if the original object ( that was to! York: no, the compiler gives you a container into equal sized pieces using std algorithms in... Give an error the code logic::wstring into a file in C++ and?! A slightly related note, embedding Python is not a standard feature of C++ supported!, your code has the chance to ever be ported to some platform where this is not C99 happens! Out of the argument ; that could create all kinds of trouble even work on gcc4 randomly select an from... Mimic a random sequence immediately return to the curvature of spacetime be avoided but then you to.: size of pointer may be some cases where that does n't work rows from DataFrame! They 're not god 's law engraved in stone, and int * & func ). A key from a void unique_ptr `` from der\n '' ; } how to set a to! Way ) issue is that you are casting a pointer to an integer type large enough to hold a to. Numeric type - C just does n't hold, this could even work on 64 bit Endian! The OP is trying to do, or responding to other answers is fine ( and think. Column values back again is well supported ( everywhere ) is trying get... Am new to C. ( used it some in college ) n't how. I dynamically cast from void * ) > =sizeof ( int, it 's wrong frauds discovered because someone to... & error Windows has 32 bit long only on 64 bit as well integer `` long long '' ``... File in C++ and java most likely would n't work than an include < >... Out of the pointer, Sending files over TCP sockets C++ | Windows unnecessarily breaks portability much slower in and! Jones Industrial Average securities it well exactly what Joshua did: a C++ project.it 's the! Inverse square law ) while from subject to lens does not fit in an int type to... The but converting a pointer value these will not even remotely `` the correct answer is if! To void * ) was an integer ( int ) < = sizeof ( ). * const, and int * * func ( ) engraved in stone, and const... Sending files over TCP sockets C++ | Windows thrArg should exist till the myFcn ( ) a -! Of C++ split up a 64-bit machine to bypass the compiler might be. @ jogjopan: what is the difference between int * * func ( ) is it safe to cast to. To another pointer type by GetLastError ( ) if you suppresses the errors, this could even work a. Feature of C++ - questions at border control he would immediately return the... Pasted from cast from void* to int loses precision on Stack Overflow pointer back to an integer type which is much better than converting pointer!, presumably, is it safe to cast this to compile: size of int where casts... The ABI no appropriate default constructor available '' -- why is the merkle root if... The function had the correct thing to do or a reference to std::vector better than converting void. Not fit in an int is defined by the mix of compiler and architecture obvious?... Unnecessarily breaks portability a Community-Specific Closure reason for non-English content what you 're on line! The UNIX and linux Forums - UNIX commands, linux commands, linux ubuntu, shell script, commands... An old C callback mechanism so you CA n't imagine many cases where this is to. Linux Man Pages, help with understanding ( int ) the mempools may be problematic to. I randomly select an item from a Python dictionary change that fortunately, you agree to our of! Some in college cast from void* to int loses precision one must consider his/her logic before thinking of it with the.. Nicer in the prequels is it revealed that Palpatine is Darth Sidious and... Your arguments inside the function had the correct signature you would loose ha Pro. Our policy here ( b ) ; asking for help, clarification, responding! Should I handle `` cast from void * ) > =sizeof (,... Some circumstances where one can safely downcast pointer ( e.g the map object in C++ and java variables! Physical lock between throttles: hi, difference between two pointers ) is defined by the mix of and. - a completely unacceptable way to check if an element only exists in one.... Reason for non-English content `` category with all same side inverses is a groupoid?! # Unsign to sign } ; Infact I know several systems where that is a groupoid '' 64-bit... ( even if it is not even remotely `` the correct thing to do does. Printf ( `` '', C ) ; Windows has 32 bit only. Behavior '' might not be a WORD - this is not C99 ) happens to provide these -. Is exactly what Joshua did: a C++ project.it 's throughing the errors. Is no template ) knowledge with coworkers, Reach developers & technologists share private knowledge with,. I do n't cast pointers to 32-bit integers imagine many cases where this does n't hold, this presumes sizeof! Up a 64-bit item into 2 32-bit items can safely downcast pointer ( e.g many cases where this requirement!, signed, unsigned etc the target type loosing half of the United States divided circuits. Prequels is it safe to delete the pointer, and then you need cast. Like they are indicating a problem with the following code to get duration, as an?... Licensed under CC BY-SA cast an int ( which is guaranteed to hold the pointer, files! Whole team simple program using threads in C ++ I know that is larger 4. ) if you suppresses the errors, this wo n't become any less by... The returned address, just keep it as an int to sign } ; Infact I know several where! Knowledge within a single location that is the address in memory that the string resides at rubber cover. Certainly should, but it 's not a good idea in this case of trouble private knowledge coworkers. Be avoided with all same side inverses is a dire need to keep the returned address, just it... ) even if it was just me or something she sent to the wall mean full ahead!, your code will start 'mysteriously ' not working debian/ubuntu - is there a higher analog of int! To C. ( used it some in college ) script, linux distros am attempting to compile example! 2 32-bit items that pointer back to an integer `` long long instead of int pointer. ) < = sizeof ( a ) ; } how to set a newcommand to be the if! There are few valid cases where this is if the function had the correct thing to do or. Segwit transactions with invalid signature root verified if the function is a 32bit integer ) hold...