I am very new to c++ but i know a couple other languages (ie. python, java, a little C). The problem is when i compile my code and try to open a new ImGui window it gives a "undefined reference" error. I think it is a problem with how i the setup the files. both my main.cpp file and the imgui library are in the same directory and when i try to import the file by using "#include "imgui/imgui.h" " it still gives my the undefined reference error. I have tried to pull all the .h and .cpp files out of the imgui folder and into the same directory as my "Main.cpp" file but it still gives me a undefined reference error. I have read the install instructions where you put the .cpp files into the working directory and it still didn't work and gave me the same error. Any help would be appreciated.
--------------------------------------------MyCode--------------------------------------------
#include <iostream>
using namespace std;
#include "imgui/imgui.h"
int main(){
ImGui::Begin("Window");
ImGui::End();
}
---------------------------------------------Output---------------------------------------------
/tmp/ccMXHI3r.o: In function `main':
Main.cpp:(.text+0x16): undefined reference to `ImGui::Begin(char const*, bool*, int)'
collect2: error: ld returned 1 exit status
-------------------------------my working directory-----------------------
imgui // imgui library folder that i downloaded from github
Main.cpp // my cpp file where my code is
The problem seem to be a missing linking step, you need to tell your compilation/linking process to link to imgui library.
When you include a header in C/C++ you are just letting the compiler to know the signatures of functions and other declarations.
Then you need to let your linker know where to look for the code, and that will be telling it to link to the library.
For example with gcc you can make a compilation + linking with the following call:
gcc foo.c -o foo -ldynLib
that example will compile the source code 'foo.c', will generate an object for that and it will link it with the dynamic library 'dynlib' into the final binary 'foo' (the executable).
in your case it could be something like this:
gcc Main.cpp -o program -limgui
Of course flags and steps will depend on your compiler / linker, also you should check the actual name of the library (imgui is just a guess, as I don't know that library)
Related
I am trying to compile a simple project which uses one of my headers. I am on Windows and I am using MinGW-W64-builds-4.3.5 Suppose the project is called test.cpp and I want to compile it using my headerosmanip which requires also the linking of its created static library libosmanip.lib. The static library has been compiled and created in MSYS2 and then copied into Windows filesystem. If I try to compile with:
g++ -std=c++17 -losmanip .\test.cpp
To search for the system headers and library path I did:
g++ -v test.cpp
and decided to put headers into C:\MinGW\bin\..\lib\gcc\i686-w64-mingw32\8.1.0\include\c++ and the static library into C:\MinGW\lib\gcc\i686-w64-mingw32\8.1.0\.
I got the following error:
C:/MinGW/bin/../lib/gcc/i686-w64-mingw32/8.1.0/../../../../i686-w64-mingw32/bin/ld.exe:
cannot find -losmanip
collect2.exe: error: ld returned 1 exit status
I've tried also by adding the -L option, linking the library path, or editing the LIBRARY_PATH variable ( $Env:LIBRARY_PATH+=";C:/MinGW/bin/../lib/gcc/i686-w64-mingw32/8.1.0/"), but it still doesn't work.
I tried to move the library into the same folder of the test.cpp file and compile, but again the same error occurs.
It's strange because I tried same thing on Ubuntu, MacOS, MSYS2 and Cygwin64 and it works.
Can you help, me please?
I finally solved the issue. The problem was related to the fact the the suffix of my library was .lib. By changing it in .a and rebuilding the library passing the correct static library name to the ar command the problem disappeared.
I'm using gcc on WSL to compile a C++ Linux project. I wanted to use the base64 encode/decode library so I installed it with vcpkg. I'm including the library's functions via #include <cpp-base64/base64.h>. However, this causes a linker error:
undefined reference to `base64_encode[abi:cxx11](unsigned char const*, unsigned int)'
Upon investigating the include directory, I see nothing unusual:
/bin/vcpkg/installed/x64-linux/include/cpp-base64$ ls
base64.cpp base64.h
As a test I decided to copy the base64.cpp into my source code directory directly and it linked correctly. Why is this happening? Shouldn't the linker pick up the base64.cpp implementation from the include directory without any problems?
I guess I just made a simple mistake but I'm not getting which..
Anyways I'm working on a library, also I'm using cmake to build the Makefiles for the project: https://github.com/immapoint/NaNO3/blob/master/CMakeLists.txt
Everything works just fine when compiling the library; it builds the following Files:
bin/libNaNO3.dll
lib/libNaNO3.dll.a (I don't like that name as well)
To test the whole thing, I got another project set up, also using cmake. https://github.com/immapoint/NaNO3TestApp/blob/master/CMakeLists.txt
The main file to test the library looks like this:
https://github.com/immapoint/NaNO3TestApp/blob/master/src/main.cpp
But when it comes to compiling the main file, I'm getting following errors:
CMakeFiles/NaNO3TestApp.dir/objects.a(main.cpp.obj):main.cpp:(.text+0xbf): undefined reference to `nano::Event<int>::attach(std::function<void(int)> *)`
CMakeFiles/NaNO3TestApp.dir/objects.a(main.cpp.obj):main.cpp:(.text+0xd3): undefined reference to `nano::Event<int>::notify(int)`
[...]ld.exe: CMakeFiles/NaNO3TestApp.dir/objects.a(main.cpp.obj): bad reloc address 0x8 in section `.rdata'
This error occures whether I'm building the project using make/cmake or compiling the source file directly using
g++ -Wall -pedantic -ansi -std=c++0x main.cpp [-L./lib -I./include] -lNaNO3
So the problem seems not to lie in cmake but in ld.
I'm working with CMake version 2.8 and MinGW containing GCC version 4.7.2.
Additional information:
Compiler output with -fPIC:
This has nothing to do with CMake or the linker. You need to include the definitions for the nano::Event member functions in the header, not in a separate source file, since templates are instantiated at compile time. By the time the linker gets there, it's too late.
For a fuller explanation, see Why should the implementation and the declaration of a template class be in the same header file? and http://www.parashift.com/c++-faq-lite/templates-defn-vs-decl.html
I'm trying to include some networking code into my C++ application. I downloaded CSimpleSocket and I copied all the .h and .cpp files into the directory where my main file is. Then I tried including one of the headers, but the linker just barfs up a bunch of errors, like:
[Linker error] undefined reference to CPassiveSocket::CPassiveSocket(CSimpleSocket::CSocketType)'
[Linker error] undefined reference to `CSimpleSocket::Initialize()'
[Linker error] undefined reference to `CPassiveSocket::Listen(unsigned char const*, short, int)'
[Linker error] undefined reference to `CPassiveSocket::Accept()'
and others. Everything is in one directory, so I don't think that's the problem. The code I'm using to include is #include "PassiveSocket.h". I'm using Dev-C++, if that makes any difference. I don't understand what I'm doing wrong, so if somebody could help me, that would be great.
Forgive me if this is a really dumb question, but I'm trying to learn C++, and it's not easy. Thanks for your help.
The reason you're getting this error is because your compiler can't find the binary that corresponds to the CSimpleSocket headers. It's as if you wrote
void someFunction(int someArg);
And then never provided the implementation for someFunction.
To use a third party library you need two things:
Header files (.h, .hpp, etc...)
Library files (.a, .lib, etc...)
Once you've got your header files and library files you need to put them in a place your compiler can find them. This place will vary depending on your OS, environment variables and compiler configuration.
Now that they're somewhere the compiler can find them you need to tell the compiler to use them. Header files are used with the #include command and library files are linked by providing arguments to the compiler.
Behind the scenes Dev-C++ uses the MinGW GNU GCC compiler, it invokes a command similar to g++ file1.cpp file2.cpp ... filen.cpp -o filename that tells the program g++ to compile a C++ executable named "filename" using files 1 to n. There are other flags that can be added to g++ such as telling it where to search and what to link.
The name of the CSimpleSocket library when compiled is "clsocket" so we need to find a way to configure Dev-C++ to add -lclsocket to the g++ command. I don't use Dev-C++ so I can't help you here but you're probably looking for "Linking Options" or something similar in your compile configuration. You also need to make sure the .lib and .h files are on the search path which should also be configurable in Dev-C++.
CSimpleSocket also provides an installer that should automatically create the .lib file and place the .lib and .h in places where they can be found, you should consider using that installer.
I think the complexity of this answer highlights the abysmal state of the C++ library integration ecosystem. Unfortunately there is no concept of a "module" in C++ at the time of writing.
I'm learning c++ and I'm trying to use a library that I've downloaded from internet in my program ( from here https://mattmccutchen.net/bigint/).
Because I want everything to be quite tidy, I put all the .hh files in a subfolder named "BI".
However when I try to compile my .cpp file with g++ (It's MinGW on Windows XP SP3), the compiler outputs the following error:
J:\comp proj\FS>J:\Programmi\MinGW\bin\g++.exe "J:\comp proj\FS\test.cpp" -o "J:\comp proj\FS\test.exe" -I "J:\comp proj\FS\BI"
E:\DOCUME~1\MrJackV\IMPOST~1\Temp\ccidH1Z6.o:test.cpp:(.text+0x2c): undefined reference to BigInteger::BigInteger(int)'
E:\DOCUME~1\MrJackV\IMPOST~1\Temp\ccidH1Z6.o:test.cpp:(.text+0x11b): undefined reference tooperator<<(std::ostream&, BigInteger const&)'
E:\DOCUME~1\MrJackV\IMPOST~1\Temp\ccidH1Z6.o:test.cpp:(.text$ZNK10BigIntegermlERKS[BigInteger::operator*(BigInteger const&) const]+0x29): undefined reference
to `BigInteger::multiply(BigInteger const&, BigInteger const&)'
collect2: ld returned 1 exit status
I've tried using the -I, -l and -L switches to fix the problem but with no success.
Moreover I've tried in the cpp to put #include "BI/BigIntegerLibrary.hh" but that didn't work.
Is there something I'm doing wrong?
Thanks in advance.
You need to use both -L and -l switches. -L to point to the directory containing the library binary, -l to name that binary
e.g. -L/home/ed/libs -lmath
There's two keywords to keep in mind. Undeclared means the compiler has never heard of it. Undefined means the compiler has heard of it, but doesn't know exactly how to use it. For those errors you need to tell it to link with the BigInteger library that should have come with the headers (A *.lib file) I'm hot sure exactly how gcc includes link libraries (Ed Heal says -L and -l, I'd do that).
Your problem is that you didn't link with the library code.
Read the "README", then follow its advice to adapt the enclosed Makefile.
Ok, so after some messing around I figured out that I needed to do a couple of things
add the -L switch with the dir of the header files
add to the g++ command line all the .cc files (e.g. g++ test.cpp BigInteger.cc etc.)
put everything in a batch file for semplicity
wow, now it seems quite easy!