Cpp Linker Error Undefined Reference
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Undefined Reference To C++ Error
it? up vote 705 down vote favorite 314 What are undefined reference/unresolved external symbol errors? What are common causes and how to fix/prevent them? Feel free to edit/add your own. c++ linker-error undefined-reference c++-faq unresolved-external share|improve this question edited Aug 4 '14 at 13:33 Arno Duvenhage 805517 asked Sep 24 '12 at 22:27 Luchian Grigore 167k28293453 3 One thing to consider adding is how to deal with "undefined vtable" undefined reference to function c++ and "undefined typeinfo" errors in particular (since they are less obvious than undefined functions or variables). –Jeremiah Willcock Jul 16 '13 at 18:25 1 I've been marking this question to be a possible dupe of this one. But after going through all of your (brilliant) answers, I can't see this case covered here. I'm aware it's specific about how an IDE sets up the project type and it's linkage dependencies. But that's a such frequently asked question I think it would be worth covered (maybe just with a link to another appropriate dupe) here. If it is already, and I just didn't spot it, forget about this request/comment. –πάντα ῥεῖ Mar 3 '14 at 21:14 @LuchianGrigore 'feel free to add an answer' I preferred to add the relevant link (IMHO) your primary answer, if you'd like to permit. –πάντα ῥεῖ Mar 3 '14 at 22:36 Pretty common mistake is that you define a function as a standalone and forget the class selector (e.g. A::) in your .cpp file: You do this (wrong): void myFunc() { /* do stuff */ } Instead of this (right): void A::myFunc() { /* do stuff */ } –jave.web Mar 11 '15 at 18:45 3 If thi
error message (or “unresolved external symbol, for Visual C++ users). This is not actually a message from the compiler, but is emitted by the linker, so the first thing to do is to understand what the linker is, and what it does. Linker c++ undefined reference to class 101 To understand the linker, you have to understand how C++ programs are built. For all
C++ Undefined Reference To Constructor
but the very simplest programs, the program is composed of multiple C++ source files (also known as “translation units”). These are compiled separately, using the
Undefined Reference To C++ Static Variable
C++ compiler, to produce object code files (files with a .o or a .obj extension) which contain machine code. Each object code file knows nothing about the others, so if you call a function from one object file that exists http://stackoverflow.com/questions/12573816/what-is-an-undefined-reference-unresolved-external-symbol-error-and-how-do-i-fix in another, the compiler cannot provide the address of the called function. This is where the the linker comes in. Once all the object files have been produced, the linker looks at them and works out what the final addresses of functions in the executable will be. It then patches up the addresses the compiler could not provide. It does the same for any libraries (.a and .lib files) you may be using. And finally it writes the executable file out to https://latedev.wordpress.com/2014/04/22/common-c-error-messages-2-unresolved-reference/ disk. The linker is normally a separate program from the compiler (for example, the GCC linker is called ld) but will normally be called for you when you use your compiler suite’s driver program (so the GCC driver g++ will call ld for you). Traditionally, linker technology has lagged behind compilers, mostly because it’s generally more fun to build a compiler than to build a linker. And linkers do not necessarily have access to the source code for the object files they are linking. Put together, you get a situation where linker errors, and the reasons for them, can be cryptic in the extreme. Undefined reference Put simply, the “undefined reference” error means you have a reference (nothing to do with the C++ reference type) to a name (function, variable, constant etc.) in your program that the linker cannot find a definition for when it looks through all the object files and libraries that make up your project. There are any number of reasons why it can’t find the definition – we’ll look at the commonest ones now. No Definition Probably the most common reason for unresolved reference errors is that you simply have not defined the thing you are referencing. This code illustrates the problem: int foo(); int main() { foo(); } Here, we have a declaration of the function foo(), which we call in main(), but no definition. So we get the error (slightly edited for clarity): a.cpp:(.text+0xc): undefined reference
files, but I didn't figure out how I can make the main program work. The errors http://www.cplusplus.com/forum/beginner/25188/ that appear (when I try to compile the source files) are: http://www.computing.net/answers/programming/dev-c-compier-just-not-working-/24305.html 1. median.cpp 1
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[Linker error] undefined reference to `WinMain@16' ld returned 1 exit status 2. grade.cpp 1
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[Linker error] undefined reference to `median(std::vector<double, std::allocator<double> >)' [Linker error] undefined reference to `WinMain@16' ld returned 1 exit status 3. student_info.cpp 1
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[Linker error] undefined reference to undefined reference `WinMain@16' ld returned 1 exit status 4. 4_data_headers_partitioning.cpp (the main program) 1
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[Linker error] undefined reference to `read(std::istream&, Student_info&)' [Linker error] undefined reference to `compare(Student_info const&, Student_info const&)' [Linker error] undefined reference to `grade(Student_info const&)' ld returned 1 exit status I attached the source files here: http://www.2shared.com/file/US8dNvZz/partitioning.html Can you help me a little? undefined reference to What I do wrong? Or what I omit? Thanks in advance for your help. (I'm using dev c++ 4.9.9.2 under windows) Jun 19, 2010 at 1:14pm UTC magnificence7 (188) I can't find where to download your files, maybe posting it helps? Anyway, are you sure you've compiled all your source files before linking? Jun 20, 2010 at 1:55am UTC Zhuge (4635) It seems like you are trying to compile all the cpp files as separate programs (hence, looking for WinMain in the other cpps). I don't know how dev c++ works, but there is probably a way to specify a "project" or something that indicates that your files are together a single program. Jun 20, 2010 at 1:56pm UTC Duoas (10440) Yes, start Dev-C++ and create a new Project. Add your main program's cpp file, then add the other cpp files you intend to use in your project. Make sure you create a "Console Application" project -- not a Windows (GUI) application project. Then use
Database CPUs Solaris Novell OpenVMS DOS Unix Mac Lounge Login» Register» Connect» Hardware & Devices ▼ General Hardware CPUs/Overclocking Networking See More... Software ▼ Security and Virus Office Software PC Gaming See More... Operating Systems ▼ Windows 10 Windows 8 Windows 7 Windows XP See More... Off-Topic Tags How-tos Drivers Ask a Question Computing.NetForumsProgrammingC/C++ Solved DEV C++ Compier just NOT working :/ Tags:Programmingerror message Xploit February 12, 2011 at 09:06:33 Specs: Windows 7 I have no idea why it's not working. I thought i may be writing programs with poor syntax or something but even when i run the example programs. It shows errors D: Here's some example code:#include