Linker Error Undefined Reference To
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Linking Error Undefined Reference To Function
up Linker Error C++ “undefined reference ” [duplicate] up vote 9 down vote favorite 2 Possible Duplicate: What is an undefined reference/unresolved external symbol error and how do I fix it? Trying to compile my program via g++ -o prog1 main.cpp -std=c++0x I get the error: /tmp/cc1pZ8OM.o: In function `main': main.cpp:(.text+0x148): undefined reference to `Hash::insert(int, char)' collect2: error: ld returned 1 exit status undefined reference error in c main.cpp #include
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Undefined Reference To Static Variable C++
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Undefined Reference To C++ Linux
Stack Overflow is a community of 6.2 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up What is an undefined reference/unresolved external symbol error and how http://stackoverflow.com/questions/14557657/linker-error-c-undefined-reference do I fix it? up vote 712 down vote favorite 317 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 167k28295455 3 One thing to consider adding is how http://stackoverflow.com/questions/12573816/what-is-an-undefined-reference-unresolved-external-symbol-error-and-how-do-i-fix to deal with "undefined vtable" 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 1 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 */ } &ndash
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 https://latedev.wordpress.com/2014/04/22/common-c-error-messages-2-unresolved-reference/ what the linker is, and what it does. Linker 101 To understand the linker, http://www.keil.com/support/docs/3136 you have to understand how C++ programs are built. For all 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 C++ compiler, to produce object code files (files with a .o or a .obj extension) which contain machine code. Each object code undefined reference file knows nothing about the others, so if you call a function from one object file that exists 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 undefined reference to 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 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 u
30 Days In the Last 90 Days In the Last 6 Months Technical Support Overview Search Contact Assistance Request Feedback Support Resources Support Knowledgebase Article Index Top 10 Articles Product Manuals Application Notes Downloads Product Updates Discussion Forum Books Product Information Software & Hardware Products ARM Development ToolsC166 Development ToolsC51 Development ToolsC251 Development ToolsDebug AdaptersEvaluation Boards Product Brochures Newsletters Home/Technical Support GCC: LINKER ERROR (UNDEFINED REFERENCE WITH C++) Information in this article applies to: GNU C Compiler for ARM All Versions SYMPTOM The GNU linker gives error messages while linking an application which contains class declarations and class instances. CAUSE The class declaration specifies a constructor and/or destructor, but the constructor/destructor function is missing. class clf { public: clf(); // Constructor (ctor) ~clf(); // Destructor (dtor) int n1, n2, n3; }; clf clf1; // class object int main (void) { return (0); } The linker gives the error messages which look like the following ones: .\obj\blinky.o(.text+0x40): In function '__static_initialization_and_destruction_0': /cygdrive/c/Keil/ARM/GNU/Examples/Blinky/blinky.cpp(92): error: undefined reference to 'clf::~clf [in-charge]() 'blinky.o' (.text+0x44):blinky.cpp:92: undefined reference to 'clf::clf[in-charge]()' RESOLUTION Add the constructor(s) and/or destructor(s) as shown below: class clf { public: clf(); // Constructor (ctor) ~clf(); // Destructor (dtor) int n1, n2, n3; }; clf::clf () { // define ctor n1 = n2 = n3 = 0; } clf::~clf() { // define dtor } clf clf1; // class object int main (void) { return (0); } SEE ALSO µVision DEBUGGER: SOURCE LEVEL DEBUGGING WITH GNU ARM Last Reviewed: Monday, December 10, 2012 Did thi