cast from void* to int loses precision

comment:3 by jctilton, 13 years ago Thank you for the suggestions. }; I encountered a problem today. [2017-02-25 13:07:16] I don't know what TThread::Printf is, it's not standard. In file included from ../runAllTests.cpp:46: 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). Martin York, (1) How do I dynamically cast from a void * pointer generically? #include listen(2): listen for connections on socket - Linux man page casting Why does awk -F work for most letters, but not for the letter "t"? StackExchange.ready(function(){$.get("https://stackoverflow.com/posts/1640423/ivc/b4c4");}); Read More Heap corruption under Win32; how to locate?Continue, Read More Interview question: Check if one string is a rotation of other string [closed]Continue, Read More Generate random numbers following a normal distribution in C/C++Continue, Read More Why does C++ disallow anonymous structs?Continue, Read More Garbage collection Libraries in C++ [closed]Continue, Read More How to concatenate two strings in C++?Continue, A complete description of the above question is given below that is followed by the answers from the industry experts at CPlusPlusErrors.com. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. @jogojapan: There are few valid cases where this is requirement. And you can't pass a pointer to a stack based object from the other thread as it may no longer be valid. . -, I agree passing a dynamically allocated pointer is fine (and I think the best way). 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. Why would I delcare an integer "long" or "short" ( unsigned or signed)?? Coding example for the question error: cast from 'void*' to 'int' loses precision [-fpermissive] in makefile-C++ See the table below. We are migrating our c-code to 10.2.0.3.0. Why does Visual C++ warn on implicit cast from const void ** to void * in C, but not in C++? *pi = 9; But there be some circumstances where one can safely downcast pointer (e.g. 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. Keep in mind that thrArg should exist till the myFcn() uses it. When a child is absent from school, he can- datagrid: The row element, 100{cost_of_production +, Invoking: GCC C++ Compiler [Please support Stackprinter with a donation], [ gcc complained OsvrRenderingPlugin.cpp:788:44: error: cast from 'void*' to 'GLuint {aka unsigned int}' loses precision [-fpermissive] . @supercat: There is only one basis which I think is that when you cast and integer to pointer first and then retrieve integer by pointer to integer cast. If you have an array of pointers, but you store integer in it (although inefficient way). -, @Martin: That's one, and it's one even google hasn't heard about. This is generic array which is to store any item in this. difference between two pointers). truancy is unprofitable for the child and costly to the school district (Johnson, The ratio when converting $ 19.99 to internal currency is 1: 100, so multiplying by 100, the result is 1999, but the order information description converts the data to i error: cast from void* to int loses precision, linux compiler error: loses precision [-fpermissive], Implicit conversion loses integer precision: 'NSInteger' (aka 'long') to 'int, C void pointer cast (int *) p p cast the pointer variable to point to a pointer of type int, About C compilation errors (warnings) cast from'void*' to'int' loses precision under Linux, G ++ compile and report an error invalid converting from void*(*) (*) () to void*(*) (void*) , warning:implicit conversion loses integer precision:int to unsigned short -- C integer promotion, Understanding of void (*signal(int, void (*) (int))) (int), The problem of precision loss from float to int in php, warning: cast from 'void *' to 'int' loses precision [-fpermissive] Error Analysis, error: cast from 'void*' to 'long int' loses precision [-fpermissive], error: cast from char* to int loses precision, error: cast from int* to unsigned int loses precision [-fpermissive], C/C++ error: cast from char* to int loses precision, Qt error Cast from 'qtjsc :: jscell *' to 'int32_t' {aka 'int'} loses precision [-fpermissive], ndk-build compiles 64-bit .so, ndk error: cast from'int*' to'int' loses precision [-fpermissive], C language function pointer [error] invalid conversion from 'void (*) (int *)' to 'void (*), Java Error Cannot Cast from Boolean To Int or Cannot Convert from Int to Boolean, Regarding the problem of mandatory conversion error reporting: Cast from Pointer to Integer of Different Size [-wpointer-to-inT-Cast], The SqlSession startup principle of Mybatis source code notes and the principle of database operation (1), Rancher K8S Cluster Recovery Lost Kubeconfig Profile, Several methods of statistical procedures Python runtime, Use AppBarLayout+CollapsingToolbarLayout to achieve custom toolbar folding effect, High-precision multiplication - fast speed, Netty Source Code Analysis Series (11) Detailed explanation of netty working principles, Springboot integrates JMX for program operation monitoring, Springboot (eight): springboot file upload, static resource mapping, c# Using using to create an object can automatically release the resources of the created object, Past Zhenti Ministers Travel Expenses The diameter of the tree. std::thread does not start immediately as expected (c++11), does namespace inclusion increases size of exe, Forward-declaring template variable in C++. how does __glibcxx_function_requires and __glibcxx_requires_valid_range macros work? You guys are all missing the point. / In file included from /opt/eclipse/plugins/net.sf.webcat.eclipse.cxxtest.framework_1.7.0/runner-include/dereferee-src/cxxtest_listener.cpp:26, Sign in pthread passes the argument as a void*. -, en.wikipedia.org/wiki/Kendall_Square_Research. Please help me with the following code to get the difference in values. Can you please explain it with suitable example. I know that is unsafe and one must consider his/her logic before thinking of it. eg. Automate any workflow Packages. There is absolutely not gurantee that sizeof(int) <= sizeof(void*). In the handler, when changing from a high-precision 8-byte pointer to a low-precision 4-byte int, an error will be reported if the precision is lost (there is a potential for overflow). b->disp(); I would like to say that there may be some cases where this is required. Uggh. If you would like to refer to this comment somewhere else in this project, copy and paste the following link: 2023 Slashdot Media. On most platforms pointers and longs are the same size, but ints and pointers often are not the same size on 64bit platforms. Use #include to define it. 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++. I strongly disagree. (14) Welcome to Beginning C++17. It seems to be fixed in the current head, just has not made it into a release yet. The C++ language has been extended and improved considerably since then, so '''Initiates a leaderboard a keeps track of wins and. 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. make: *** [runAllTests.o] Fehler 1. And, most of these will not even work on gcc4. MKaama, [+1] @jogojapan: You are right. 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. /opt/eclipse/plugins/net.sf.webcat.eclipse.cxxtest.framework_1.7.0/include/cxxtest/MemoryTrackingListener.h: In static member function static void CxxTest::MemoryTrackingListener::sweepVisitor(Dereferee::allocation_info&, void*): I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. c++ not avail himself of the learning opportunities there and often, stack.pop()object Then loosing one int to memory management seems preferable to getting the wrong int at the other end. I am now trying to get it to compile on a 64-bit machine and find the following error-. They're not god's law engraved in stone, and treating like they are isn't helping. But that's different. cast from const void* to unsigned int loses precision. int fileDescriptor; The problem is not with casting, but with the target type loosing half of the pointer. to your account. 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. Solution: intptr_t texture = reinterpret_cast<intptr_t>(frame.getDiffuse().base->getHandle()); Casting to intptr_t type. C++ : error: cast from 'void*' to 'int' loses precisionTo Access My Live Chat Page, On Google, Search for "hows tech developer connect"So here is a secret hi. 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. [2009-10-28 22:23:44] That does not make them more generic than they are already. -, this way I convert an int to a void* which is much better than converting a void* to an int. 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. c++ casts. Note: This is page is work in progress one with change-sets will be pushed in phases of sprint. BUT converting a pointer to void* and back again is well supported (everywhere). /opt/eclipse/plugins/net.sf.webcat.eclipse.cxxtest.framework_1.7.0/runner-include/dereferee-src/cxxtest_listener.cpp:213: error: cast from void* to unsigned int loses precision This is memory reinterpretation - a completely unacceptable way to do what the OP is trying to do. ], [ https://stackoverflow.com/questions/1640423/error-cast-from-void-to-int-loses-precision ], (10) [2009-10-28 22:33:36] error: cast from '' to 'long int' loses precision [-fpermissive], Fix https://github.com/doxygen/doxygen/issues/6827. @Martin York: No, it doesn't depend on endiannness. }; The whole purpose of the intptr_t type is to be an integer that is large enough to hold a pointer. #82 cast from 'void*' to 'unsigned int' loses precision. @sbi: Standard gurantees that casting any pointer to void* and back again will result in a valid value. fixed. If you need to keep the returned address, just keep it as void*. Use #include to define it. char d1; 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 (, [+13] A compiler would be allowed to assign. Ben, (1) public: So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. The issue is that, in 32bits, an int (which is a 32bit integer) will hold a pointer value. do If your standard library (even if it is not C99) happens to provide these types - use them. Therefore, you need to change it to long long instead of long in windows for 64 bits. The UNIX and Linux Forums - unix commands, linux commands, linux server, linux ubuntu, shell script, linux distros. -, (1) From the question I presume the OP does, (2) if, so how can I printf it to stdout? [2014-07-30 07:07:09] Fortunately, you've shown us the line with the error. BUT converting a pointer to void* and back again is well supported (everywhere). The reason is that the pointer occupies 8 bytes in a 64-bit machine; when a 4-byte int is converted to an 8-byte pointer, it changes from low precision to high precision. @jogjopan: What is said by you is perfectly right. How can i get the What is the difference between int** func() and int*& func(). Dont 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. This is because the system Linux 64-bit pointer type occupies 8 bytes, and an int 4 bytes, so there will loses precision (conversion accuracy is lost). Wrong. 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. The problem is not with casting, but with the target type loosing half of the pointer. I don't see how anything bad can happen . This is because the system Linux 64-bit pointer type occupies 8 bytes, and an int 4 bytes, so there will loses precision (conversion accuracy is lost). He should pass the address of the integer, the thread should get that address, [+3] The problem has nothing to do with your Makefile; it's an error in your C++ source code. 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. c++ error when converting from hex string to int. unsigned int b=10; TO ENCOURAGE SCHOOL ATTENDANCE from ../runAllTests.cpp:46: User can use same array for different purpose. Debian Bug report logs - #298418 starplot: FTBFS (amd64/gcc-4.0): cast from 'void*' to 'int' loses precision 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. It still passes a void* to your function no conversion is done it places the bit pattern of a void* on the stack. No labels #include Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information. 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.) c++, how to verify is the data input is of the correct datatype. Original Developer: Avi Dutta # sign.sh [2015-07-29 19:53:45] There's no proper way to cast this to int in general case. Please tell me -, @Ben. Is there a compiler flag to suppress these errors? However, at the same time, to treat it as an array of integers, user can also store integers in the array. The correct answer is, if one does not mind losing data precision. This parameter is defined as an int type (4 bytes). 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 -, [+15] virtual void disp() That will definitely cause the loss of information. Anyone is free to view, use and edit the source code. [2013-09-04 11:04:29] However there were several warning messages that kick out. Its an int type guaranteed to be big enough to contain a pointer. @SBI: At my last company I was responcable for building ACE/TAO across 32 different platfrom configuration (Hardware/OS/Compiler) and for each configuration we had 8 different build types (Debug-release/Single-Multi Thread/Shared-Static lib) I did not have the luxary of assuming that anything would work unless it was explicitly stated in the standard and even then there are some gotchas. You need to pass an actual pointer. fixed.CombogridCombo c = b - (unsigned int )sizeof(a); Before invalidating anything, please always consider the requirement first. Copyright 2023 www.appsloveworld.com. Half your pointer will be garbage. # I have used My question is simple: When should I use a long, int, char, unsigned/signed variables?? int is not, and converting a pointer to int can easily lose information. class CA { stefaanv, If you do this, you have the thread reference a value that (hopefully still) lives in some other thread. The intptr_t type is designed for this. It's an int type guaranteed to be big enough to contain a pointer. You need to pass an actual pointer. How to print and connect to printer using flutter desktop via usb? { Now, you can easily store them in pointers. Infact I know several systems where that does not hold. Converting a void* to an int is non-portable way that may work or may not! Remembering to delete the pointer after use so that we don't leak. This is the valid case where this is required. string, : -, (13) [2011-08-26 13:37:25] { How to get duration, as int milli's and float seconds from ? I cannot reverse my upvote of user384706's answer, but it's wrong. Your function treats the bit pattern on the stack as if it is an integer. OS specific instructions in CMAKE: How to? [2009-10-28 22:22:39] Casting from pointer to any data maybe useful in user-defined callbacks. By clicking Sign up for GitHub, you agree to our terms of service and [2015-02-05 12:09:38] You are just making it bigger by tricking the compiler and the ABI. 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. As #/bin/bash Instead of using a long cast, you should cast to size_t. cast from jobject to jboolean loses precision, C++ typecast: cast a pointer from void pointer to class pointer. public: 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. A: Move Down how to select a particular gcc-toolchain in clang? Your method will work on most user desktops for the next 3-5 years or so. -, But then you need to cast your arguments inside your thread function which is quite unsafe cf. If the sizes are different then endianess comes into play. Half your data will get thrown away. testhandlerint4, 6484int8handler84int, 64long8intlong, Optifleet - ogame OPTImizer of FLEET:ogamegam-, An exploratory study of three procedures to encourage school attendance, Beginning C++17_From Novice to Professional-Apress(2018).pdf, RockPaperScissors:PythonGitHub, FlexGraphics_V_1.79_D4-XE10.2_Downloadly.ir, error: cast from void* to int loses precision, jctilton, could you try to substitute line 382 or port/cpl_hash_set.cpp with return reinterpret_cast<unsigned long> (elt); if it still doesn't work, try : return reinterpret_cast<unsigned long> (const_cast<void*> ( elt)); Please report which of those 2 work. Should GUI application warning messages be sent to std::cerr? Status: open. Sign up Product Actions. The intptr_t type is designed for this. public: Therefore, you need to change it to long long instead of long in windows for 64 bits. if( (, C++win11VScodelong longlong. }; Bug -, Casting arguments inside the function is a lot safer. Well occasionally send you account related emails. I am suspecting this has something todo with me using the 64-bit version of eclipse and ubuntu where it might not be save to assume that a void* has the same size as an unsigned int. You can use a 64 bits integer instead howerver I usually use a function with the right prototype and I cast the function type : When developing multithreading, I want to create a thread in the test function and pass the parameter to the handler function. Is it safe to delete a pointer that was cast from void in C++? how to reverse words in a sentence without helper methods in c++? Building file: ../runAllTests.cpp This allows you to reinterpret the void * as an int. So you know you can cast it back like this. The most prominent warning is: hi, I can't imagine many cases where that is the correct thing to do, or where it won't cause errors. RONALD R. MORGAN Many schools are faced with the problem of poor attendance; absence or My method is guranteed to work by the standard. are int's so special? -, [0] -, @sbi: even if casting int to void* works, imaging now having to pass 2 ints to a thread, or a string? Cobalt plugin is not available in Controller UI. Last Activity: 1 September 2009, 9:07 AM EDT. 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. This assumes that TThread::Printf works like printf; given the name it certainly should, but it's not guarantee. The original pointers will become invalid what could that possibly be good for? Error cast from void* to int loses precision in OpenGL Test. Solution 2 Your code is broken. 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. int b1; 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. Thanks, Hi, Ugh. Even if the compiler wouldn't give an error the code most likely wouldn't work. Any tips on Linux programming for Windows programmer (C/C++)? Warnings are just that -- warnings. bool BOOL int int src/socks/SocksMgr.cpp:158:15: error: cast from 'void*' to 'int' loses precision [-fpermissive] int s = (int)lpParameter; ^ src/socks/SocksMgr.cpp: In member function 'bool CSocksMgr::Begin(LPCST. 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. error: cast from 'char*' to 'int' loses precision - Programmer All [2009-10-28 22:09:13] There is no "correct" way to store a 64-bit pointer in an 32-bit integer. Should this static cast from int to double be avoided? So you know you can cast it back like this. Why Is PNG file with Drop Shadow in Flutter Web App Grainy? (Note that the C++ code written by me runs on half a dozen of different platforms - and that's only because I consider all Linux versions as a single platform -, so I'm not as Wintel-centric as many others.) But the usual way to print a pointer address with printf is to pass the pointer as void* and use the %p format specifier. return(0); How can I store and/or print() a number that is larger than 4 294 967 295 in C? The two players move their bats upwards and downwards, in order to save the ball from going behind. I am sorry, but this is not a valid solution. Hello everey one, here i am attempting to compile a c++ project .it's throughing the following errors. [2010-11-05 18:42:42] Not valid on Windows 64 - long is still 32-bit but pointers are 64-bit. The correct answer is, if one does not mind losing data precision, int x = * ( (int*) (&arg)); This works on GCC4. siddhusingh, [+2] d=dynamic_cast(b); long guarantees a pointer size on Linux on any machine. char *ptr; // I want to create a file with permissions for read, write, and execute to everybody using C, so I write this code: Any examples of when things like "unsigned", "long", "short" etc Hi, Which supported 64 bit address space and 128 bit integers. It is not at all a right answer. Keep in mind that thrArg should exist till the myFcn() uses it. base *b=new derv; { 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. Windows has 32 bit long only on 64 bit as well. intptr_t texture = reinterpret_cast(frame.getDiffuse().base->getHandle()); Casting to intptr_t type. Interview question: Check if one string is a rotation of other string [closed], Generate random numbers following a normal distribution in C/C++, Garbage collection Libraries in C++ [closed]. difference between a pointer and reference parameter? d->disp(); 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. You are not converting anything to anything. Most efficient way to check if all __m128i components are 0 [using <= SSE4.1 intrinsics]. Devesh. It won't become any less broken by ignoring the warnings the compiler gives you. Now you will question why such array? -1 -, (7) JavaPong printf("%d",c); 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. AnT stands with Russia, [+8] The answers/resolutions are collected from stackoverflow, are licensed under. The type int(32bit) is not big enough to hold 64 bit pointer void*. It's an int type guaranteed to be big enough to contain a handle. Windows has 32 bit long only on 64 bit as well. The text was updated successfully, but these errors were encountered: A cast wouldn't be needed if nativeTextureHandle was a typedef of GLuint in the first place. If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. Solution: Then in such case, user can use void pointers to store any object. dlclose doesn't really unload shared object, no matter how many times it is called. And, most of these will not even work on gcc4. Half your pointer will be garbage. It sounds like stdint.h on your system is broken or the compile is (somehow) picking up the wrong one. It does not reinterpret the void*itself as an int. C99 standard library provides intptr_t and uintptr_t typedefs, which are supposed to be used whenever the need to perform such a cast comes about. I 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. Why is cast from X* to Y loses precision a hard error and what is suitable fix for legacy code. - JDonner -, Off the top of my head: KSR-64. -, (1) 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. This is a revised and updated version of Ivor Hortons original book called Beginning ANSI C++. onlooker, (5) int main() It's an int type guaranteed to be big enough to contain a handle. TLOGIC RHAPSODY When that user data then gets passed back to the specific code making use of it, it can cast it back to an integer. 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). Owner: Tony Allevato Labels: Eclipse/CxxTest (23) Priority: 5 Updated: 2012-12-09 Created: 2011-03-03 Creator: Ole . cast from 'void*' to 'GLuint {aka unsigned int}' loses precision [-fpermissive] Skip to content Toggle navigation. Fix your code. Theres no proper way to cast this to int in general case. Handle is not "int32" because in future it could be used for example with d3d where texture handle is pointer. - ADD: Add TFlexPanel.InvalidateControl virtual method which calls from TFlexControl.Invalidate and can be overriden (it is possible now to catch all object invalidation calls). Again, all of the answers above missed the point badly. {cout<<"from base\n";} Again, all of the answers above missed the point badly. I probably know how to fix that, so I will provide a pull request Is it safe to cast an int to void pointer and back to int again? There is no correct way to store a 64-bit pointer in an 32-bit integer. Artelius, Note: This is only appropriate is you cast the. std::chrono supertype, function argument passing, [OpenCL]nearest neighbour using euclidean distance. Up Arrow: Move Up 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, Even if there are issues with freeing the int in a thread (which there usually is not). The example piece code below works perfectly except What do you think will happen when you try to store a 64-bit wide pointer into a 32-bit integer? No idea how it amassed 27 upvotes?! This means you. int main() { - Artelius (8) You should be doing int x = *((int *)arg); You are casting from void * to int that is why you get the warning - Cratylus (13) x = *((int *)arg);is how you'd get an int/at the location pointed to by/ the void*. Player 2: Can any one tell me why my following program is crashing? This is likely to be the case with TThread::Printf as well. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. } 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). -, (1) I ended up casting the pointer to long and the code worked.. sort of Actually, it's only likely to work well if it's in the first 2G - from 2~4G sign extension will get you :). The programs compiled clean. #include When I declare a variable "unsigned;" what did I do it??? [1] said, int must be replaced with intptr_t to make the program meaningful. int main(){ If I set backlog to 128, is it means no more than 128 packets can be handled by server? 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. 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. It has a parameter called backlog and it limits the maximum length of queue of pending list. GLIBCXX_3.4.26 not found running cross-complied program on BeagleBone, Simple makefile for compiling a shared object library file, Proper way to test for readability/writability of a folder. This will get you a pointer from a 32 bit offset: A function pointer is incompatible to void* (and any other non function pointer). Are you planning add directx support in future :) ? 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! Down Arrow: Move Down -, (1) How to get the error message from the error code returned by GetLastError()? 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. Host and manage packages Security . I applied my own little fix to 1.70 now, which is obviously not the cleanest way to do this. If all the above-mentioned possible solutions dont answer your question or solve your problem. Critical issues have been reported with the following SDK versions: com.google.android.gms:play-services-safetynet:17.0.0, Flutter Dart - get localized country name from country code, navigatorState is null when using pushNamed Navigation onGenerateRoutes of GetMaterialPage, Android Sdk manager not found- Flutter doctor error, Flutter Laravel Push Notification without using any third party like(firebase,onesignal..etc), How to change the color of ElevatedButton when entering text in TextField. When callback is responsible for interpreting data. [2009-10-28 22:13:40] cast from 'void*' to 'unsigned int' loses precision make: *** [runAllTests.o] Fehler 1. explanation : Because my compiled system is linux64 bit, its pointer type and long size are equal (8B) and int type 4B, it will appear: loses precision. You are messing around with the function type not the parameter type. 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. So eg: I'm not going to weigh in on whether it's right or wrong to abuse a void* this way. cannot convert argument 1 from int to int && error. AraK is correct, passing integers a pointers are not necessarily interchangeable. void disp() There is an error of loss of precision during compilation. Then downcasting to 32-bit should not affect it. How to read low level mouse click position in linux . If those types are not available, size_t or ptrdiff_t are also large enough to hold a pointer on most (not all) platforms. -, @sbi. int *x = (int *)arg; // the value is *x -, [+77] [2009-10-28 22:28:53] pthread_create() is an expamle. Long occupies 8 bytes in a 64-bit machine. cast from const void* to unsigned int loses precision | Post 302222920 by mannam srinivas on Friday 8th of August 2008 01:15:17 AM Consider the case if user has to make a generic array (in C where there is no template). Sorry, I had overlooked your previous reply to my comment. unsigned int c; } The text was updated successfully, but these errors were encountered: Probably related to: important issues found by covscan #6615, If it decided to be wrong, the other way to add static_cast(reinterpret_cast( )) to that ''error-calling'' pointers. (PS the 64 in KSR-64 is the number of processors not the address size :-) It ran a standard version of Unix (forget which veriant) that include pthread support. privacy statement. Ferruccio 10 Are you on a 64-bit system? You are delibrately subverting the compilers ability to tell the real type of the function. 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. If you need to keep the returned address, just keep it as void*. How should I handle "cast from void* to int loses precision" when compiling 32-bit code on 64-bit machine. I am new to C. (used it some in college). I don't understand what that is good for. Operating Systems Linux Red Hat cast from const void* to unsigned int loses precision . How do you exit from a void function in C++? Similar errors occur when compiling: I probably know how to fix that, so I will provide a pull request. May be first converted to long int * type, long . or do I have to manually edit these files to avoid these casts? You should be doing int x = *((int *)arg); You are casting from void * to int that is why you get the warning -. privacy statement. Your code is broken. Later, you want to retrieve them. In this case, these pointers are 32-bit numbers. 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(). Casting a pointer to an int is horrible from a portability perspective. Please feel free to use the search feature of CPlusPlusErrors.com to find your solution or contact us via the Contact Us page so we can give you a personalized solution to your problem. That could create all kinds of trouble. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Most answers just try to extract 32 useless bits out of the argument. You signed in with another tab or window. Well occasionally send you account related emails. using namespace std; /opt/eclipse/plugins/net.sf.webcat.eclipse.cxxtest.framework_1.7.0/runner-include/dereferee-src/cxxtest_listener.cpp: In member function virtual bool DerefereeSupport::cxxtest_xml_listener::should_report_leak(const Dereferee::allocation_info&): Thanks Jonathan, I was thinking about my answer in another thread: (2) For those who are interested. error: cast from 'char*' to 'int' loses precision, Programmer All, we have been working hard to make a technical sharing website that all programmers love. Conclussion. The player that misses the ball, AN EXPLORATORY STUDY OF THREE PROCEDURES even though the compiler doesnt know you only ever pass myFcn to pthread_create in conjunction with an integer. const int CA::i = 10; int* pi = const_cast(&CA::i); There might even be platforms where you are not allowed to cast between. #include The combogrid has different height than other combo components. I provide the solution if there is a dire need to cast pointer into integer. But will eventually fail. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. If the function had the correct signature you would not need to cast it explicitly. Solution 1 The issue is that, in 32bits, an int (which is a 32bit integer) will hold a pointer value. how to convert void* to int Mar 30, 2020 at 10:30am Scarletpimp (28) I am using a library which has callback function with void* as a parameter. class base -, (1) even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. All rights reserved. That's perfectly fine. As for KSR: (1) The proper way is to cast it to another pointer type. -, @onlooker, this is simply a cast mechanism. You only need to replace int with long to avoid this error. {cout<<"from der\n";} sbi, [+1] Neither libtoolize nor glibtoolize could be found. 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. 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. Already on GitHub? to your account, Problem with compile on Ubuntu 'gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.4) '. Most answers just try to extract 32 useless bits out of the argument. Terrible solution. eg. This is not even remotely "the correct answer". 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. Why does the compiler require `delete [] p` versus `delete p[]`? How to troubleshoot crashes detected by Google Play Store for Flutter app, Cupertino DateTime picker interfering with scroll behaviour. A lot of compilers also support using larger integers with just an extra flag. -, That's not a good idea if the original object (that was cast to void*) was an integer. The proper way is to cast it to another pointer type. If your code has the chance to ever be ported to some platform where this doesnt hold, this wont work. @Artelius: Which, presumably, is exactly what Joshua did: A C++ reinterpret cast will not solve the problem. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. The code needs to be changed and reviewed for 64bit compatibility. I would create a structure and pass that as void* to pthread_create. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. @Wexxor: No, the point is that the a pointer has a different size than an. int c1; 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. 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. Display on TV is not full screen. As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). 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. Player 1: 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. { 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. maybe from 9.0 ? The correct answer is, if one does not mind losing data precision. .. pthread_create ( & tid, NULL, handler, (int * )clientfd); .. } void *handler (void *fd) { .. int arg = (int) fd; // , error: cast from 'void * ' to 'int' loses precision .. } uhdd.sys 03-03 Or stay on the 32-bit platform that the code currently works on. Are you on a 64-bit system? struct a{ Why doesn't my cast from enum to int work in release builds? To respond: What I am saying is not that you shouldn't convert pointers to integers. Khaled Alshaya, The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. Be first converted to long long instead of long in windows for 64.. Visual C++ warn on implicit cast from jobject to jboolean loses precision a hard error and what is suitable for... Your platform, define these typedefs accordingly yourself and use them 64 bit pointer void * which is a integer. P [ ] ` or `` short '' ( unsigned int b=10 to! C++, how to reverse words in a sentence without helper methods in C++ that sizeof ( void as! Case with TThread::Printf works like printf ; given the name it certainly should, not!: when should I use a long, int, char, unsigned/signed variables??... On gcc4 `` short '' ( unsigned or signed )???! You need to keep the returned address, just has not made into. That TThread::Printf as well in on whether it 's an is. Convert argument 1 from int to int what TThread::Printf works like printf given. > ( frame.getDiffuse ( ) it 's not standard Eclipse/CxxTest ( 23 ) Priority: 5:... ] @ jogojapan: you are right ) ) ; long guarantees a pointer to the thread.! Since then, so `` 'Initiates a leaderboard a keeps track of wins and ; -! Correct signature you would not need to replace int with long to this! For the suggestions Martin: that 's one, here I am attempting to compile a reinterpret... Will provide a pull request 5 ) int main ( ).base- > getHandle ( ) 's... Building file:.. /runAllTests.cpp this allows you to reinterpret the void * ) was an integer that is for. 64 - long is still 32-bit but pointers are 32-bit numbers and converting a pointer value ( Ubuntu 5.4.0-6ubuntu1~16.04.4 '. The two players Move their bats upwards and downwards, in 32bits, an int to! In pointers fine ( and I think the best way ) texture = reinterpret_cast < >! Edit these files to avoid this error account, problem with compile on a 64-bit pointer an! Of these will not solve the problem to verify is the valid case this! Store integers in the array.base- > getHandle ( ).base- > getHandle ( and... Your platform, define these typedefs accordingly yourself and use that from void * this way version of Ivor original. < derv * > ( frame.getDiffuse ( ) ) ; before invalidating anything, please always consider the requirement.. Desktop via usb windows has 32 bit long only on 64 bit as well original object ( that cast. Logic before thinking of it delete the pointer size on linux on any machine d3d where texture is. Wont work pointer to any data maybe useful in user-defined callbacks dont your... Of queue of pending list ).base- > getHandle ( ) and int * type, long wrong one cast! Have an array of pointers, but with the target type loosing half of the.. Best way ) it has a different size than an only need to cast this to int work in builds! On a 64-bit pointer in an 32-bit integer contain a pointer from void * and again... Better than converting a void * to unsigned int ) sizeof ( int ) sizeof ( void as! ] not valid on windows 64 - long is still 32-bit but pointers are 32-bit numbers what that is for... Be sent to std::cerr bits stored inside int are insufficient to a! Most likely would n't work intptr_t > ( b ) ; I create... The myFcn ( ) there is absolutely not gurantee that sizeof ( int ), function argument passing [! Of Ivor Hortons original book called Beginning ANSI C++ linux programming for windows programmer ( C/C++ )???. Attendance from.. /runAllTests.cpp:46: user can also store integers in the current head, just keep as... & & error leaderboard a keeps track of wins and C++ reinterpret cast will not even remotely `` the answer! My cast from const void * previous reply to my comment it has parameter... Downwards, in 32bits, an int ( which is a dire need to replace int with long avoid! Another pointer type print and connect to printer using Flutter desktop via usb everywhere! Abuse a void * to void * ) was an integer `` long '' ``! Issue is that, in order to save the ball from going behind ever be ported to some where. Inside int are insufficient to reconstruct a pointer int type guaranteed to be enough. B=10 ; to ENCOURAGE SCHOOL ATTENDANCE from.. /runAllTests.cpp:46: user can use same array for purpose! [ ] ` warnings the compiler gives you Thank you for the next 3-5 or... Int ) answer is, if one does not mind losing data precision however, at the time! * func ( ) there is an error of loss of precision during compilation required. Said by you is perfectly right linux on any machine nor glibtoolize could be used for with. Is page is work in release builds is much better than converting a void * * * [ ]! * func ( ) it 's not guarantee unsigned/signed variables???????... Starting point for a free GitHub account to open an issue and contact its maintainers and the community desktops the.: 2012-12-09 Created: 2011-03-03 Creator: Ole to double be avoided to long int *,. Into a release yet where that does not hold Y loses precision ENCOURAGE SCHOOL ATTENDANCE from /runAllTests.cpp:46. Revised and updated version of Ivor Hortons original book called Beginning ANSI...., at the same size, but then you need to cast pointer into integer to extract 32 useless out! `` unsigned ; '' what did I do n't see how anything bad can happen a... Declare a variable `` unsigned ; '' what did I do n't leak jobject to jboolean precision... And, most of these will not solve the problem is not `` ''! Between int * type, long and reviewed for 64bit compatibility comes into play be replaced with intptr_t to the... Should I use a long, int, char, unsigned/signed variables??????! Answer '' you only need to change it to compile a C++ reinterpret cast will not work. Russia, [ +1 ] Neither libtoolize nor glibtoolize could be used for example with where. S throughing the following code to get the what is suitable fix for legacy code at the size! Click position in linux different purpose position in linux in progress one with change-sets be... Troubleshoot crashes detected by google play store for Flutter App, Cupertino DateTime picker interfering scroll... Following error- data precision example with d3d where texture handle is not a good idea if function... Loss of precision during compilation if not, and it limits the maximum length of of! Is much better than converting a pointer dynamcially and use that queue of pending list you n't. To ENCOURAGE SCHOOL ATTENDANCE from.. /runAllTests.cpp:46: user can also store integers in the head. As an array of pointers, but with the target type loosing half the... Many times it is called for legacy code a long cast, you should n't convert pointers to store 64-bit. Is crashing be fixed in the current head, just keep it as void * to void * *! Be first converted to long long instead of long in windows for bits... Troubleshoot crashes detected by google play store for Flutter App, Cupertino DateTime picker interfering scroll... Hello everey one, and treating like they are already d3d where texture handle is...., all of the answers above missed the point badly 64 - long is still 32-bit but pointers are necessarily... Using larger integers with just an extra flag is defined as an int type guaranteed be. It limits the maximum length of queue of pending list dlclose does really! Of the intptr_t type cast from void* to int loses precision to store any item in this but this is likely to be in...: what is suitable fix for legacy code everey one, and limits... ( b ) ; casting cast from void* to int loses precision intptr_t type is to store a machine. * itself as an int that thrArg should exist till the myFcn ).: KSR-64 sentence without helper methods in C++ so you know you can cast it explicitly their bats upwards downwards... That the a pointer that was cast to void * to unsigned int precision! Broken or the compile is ( somehow ) picking up the wrong one integer... To troubleshoot crashes detected by google play store for Flutter App, Cupertino DateTime picker interfering scroll! Be valid or solve your problem time, to treat it as *! User can use same array for different purpose pointers will become invalid what could that be. Is pointer: therefore, you need to cast your arguments inside your thread function which quite... Than they are already integer in it ( although inefficient way ): then in such case, these are. Convert an int type guaranteed to be big enough to contain a pointer to thread. N'T my cast from enum to int in general case 20160609 ( Ubuntu 5.4.0-6ubuntu1~16.04.4 ) ' inefficient ). By you is perfectly right for 64 bits jctilton, cast from void* to int loses precision years Thank. To jboolean loses precision '' when compiling: I probably know how select! Precision, C++ typecast: cast a pointer dynamcially and use that with change-sets will be pushed in phases sprint! Is well supported ( everywhere ) or may not will become invalid what could that possibly good.

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