Link Error Undefined Reference
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C++ Undefined Reference To Class
each other. Join them; it only takes a minute: Sign up What causes the error “undefined reference to (some function)”? [duplicate] up vote 7 down vote favorite This question already has an answer here: What is an undefined
Undefined Reference Error In C
reference/unresolved external symbol error and how do I fix it? 25 answers I get the error: main.o(.text+0x1ed): In function `main': : undefined reference to `avergecolumns' collect2: ld returned 1 exit status when I gcc *.o. I'm not quite sure what causes this error. Other posters have explained it as the function is not found or the function is empty. If someone could clarify or refine, it would be greaty appreciated! Here is my function's code(I'm trying to linker error undefined reference to function in c calculate the average of the column in 2D arrays): #include "my.h" void averagecolumns (int x, int y, int** a) { int i; int j; float sum; float colAvg; sum = 0; colAvg = 0; printf("i. The column averages are: \n"); for(i = 0; i < x; i++) { for(j = 0; j < y; j++) { sum += a[i][j]; colAvg = sum / (float)x; } printf("Column: %3d, Average: %6.2f", j, colAvg); sum = 0; colAvg = 0; } The relavent parts of main are: #include "my.h" int main (int argc, char* argv[]) { int** a; float** colAvg; int ROWS; int COLS; int i; int j; int** table; FILE* fpmyfile; int closeResult; .... printme (ROWS, COLS, a); // call functions a - j oddvalues (ROWS, COLS, a); oddlocations (ROWS, COLS, a); countoddrows (ROWS, COLS, a); addrows (ROWS, COLS, a); findfirstsmall (ROWS, COLS, a); findlastlarge (ROWS,COLS, a); addcolumns (ROWS, COLS, a); avergecolumns (ROWS, COLS, a); .... } Also, is this a linker or a compile error (I wasn't sure which tag to add). c linker-error share|improve this question edited Nov 6 '11 at 0:49 Kerrek SB 284k40517750 asked Nov 6 '11 at 0:42 Piseagan 114239 marked as duplicate by PlasmaHH, JasonMArcher, Michael Walz, Ivan Ferić, Oz123 Jul 4 '14 at 9:23 This question has been asked before and already has an answer. If those answers do not fully address your
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
C++ Undefined Reference To Constructor
what the linker is, and what it does. Linker 101 To understand the linker, undefined reference to static variable c++ you have to understand how C++ programs are built. For all but the very simplest programs, the program is composed of multiple undefined reference to c++ linux 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 http://stackoverflow.com/questions/8024440/what-causes-the-error-undefined-reference-to-some-function 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 https://latedev.wordpress.com/2014/04/22/common-c-error-messages-2-unresolved-reference/ 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 unr
Practice Problems Quizzes Resources Source Code Source Code Snippets C and C++ Tips Finding a Job References Function Reference Syntax Reference Programming http://www.cprogramming.com/tutorial/compiler_linker_errors.html FAQ Getting Help Message Board Email About Us Dealing with Compiler Errors - Surviving the Compilation Process By Alex Allain It's your first C (or C++) program--it's https://community.particle.io/t/solved-undefined-reference-error-linker-error-when-compiling-from-web-ide/15890 not that long, and you're about to compile it. You hit compile (or enter the build command) and wait. Your compiler spits out fifty lines of text. You undefined reference pick out words like "warning and "error". Does that mean it worked? you wonder. You look for the resulting executable. Nothing. Damn, you think, I guess I have to figure out what this all means... The Types of Compilation Errors First, let's distinguish between the types of errors: most compilers will give three types of compile-time undefined reference to alerts: compiler warnings, compiler errors, and linker errors. Although you don't want to ignore them, compiler warnings aren't something severe enough to actually keep your program from compiling. Usually, compiler warnings are an indication that something might go wrong at runtime. How can the compiler know this at all? You might be making a typical mistake that the compiler knows about. A common example is using the assignment operator ('=') instead of the equality operator ('==') inside an if statement. Your compiler may also warn you about using variables that haven't been initialized and other similar mistakes. Generally, you can set the warning level of your compiler--I like to keep it at its highest level so that my compiler warnings don't turn in to bugs in the running program ('runtime bugs'). Nevertheless, compiler warnings aren't going to stop you from getting your program working (unless you tell your compiler to treat warnings as errors), so they're probably a bit less frustrating than errors. Errors a
problem is this: I have my library.cpp and library.h along with 20-30 other files (with directory structure flattened). library.cpp uses functions from another file library-helper.h, therefore library.h has an #include "library-helper.h". Now, when I compile this locally with the "firmware", using "make PLATFORM=Photon" everything works fine, I get a .bin and it runs ok. However, when I do this on the webIDE. I get: ../../../build/target/user/platform-6/libuser.a(library.o): In function XXXXXXX(unsigned char*)':
XXX/XXXX.cpp:342: undefined reference toXXXX-function' Any help appreciated! Cheers! bko 2015-09-23 21:29:40 UTC #2 Hi @jersey99 Have you tried converting to #include library-helper/library-helper.h Includes are a bit inconsistent right now between all the compile strategies, since the web IDE puts the include libraries into a temporary directory. jersey99 2015-09-23 21:31:38 UTC #3 Do you mean: In my library.h, I should say #include "library/library-helper.h" ? ScruffR 2015-09-23 21:34:01 UTC #4 If you have your own .H/.CPP files you'd stick with the #include "yourLib.h" way, but if you import a library from the Web IDE library repository it's #include "libraryName/libraryName.h" But one (or two) stupid question:You do have a line #include "library.h" in your library.cpp file and your main project file (or any other header that includes the header)?And you do have an #include "application.h" in all your headers too? bko 2015-09-23 21:41:30 UTC #5 For each automatically included library (i.e. you clicked on the library icon and say "yes, add to sketch") you get a separate directory with the name of library. For each new click of the circle-plus to add a .h and a .cpp file, you get a file in the directory with your current sketch. [Ah, I see @ScruffR beat me to it again!] One other quick point--if you have libraries that are interdependent and