Linker errors with codelite, unittest++ and g++ on linux - c++

I'm new to unit testing in c++, and writing c++ on Linux (Mint). I'm using CodeLite as my IDE. I have found several answers on stackoverflow about linker errors, but after hours of trying various solutions I have not succeeded in implementing a solution correctly.
I installed unittest++ through apt-get. The unittest++ header files were installed in /usr/include, so I added this to the Compiler linker options in Codelite (Right click project name->Settings, Compiler):
Codelite screenshot
I then have a very simple program, which consists entirely of one main.cpp file:
#include <unittest++/UnitTest++.h>
//See if unit tests are working
TEST(MyMath) {
CHECK(false);
}
int main()
{
UnitTest::RunAllTests();
return 0;
}
Running the project at this point generates a stream of linker errors other users have experienced, for example:
main.cpp:4: undefined reference to UnitTest::CurrentTest::Details()
At this point, my understanding is that I now need to tell the g++ compiler about the object files and link them to the unittest++ files. And this is where I'm stuck. The only .o file I see is in Debug/main.cpp.o and running the command
g++ main.cpp -o main.cpp.o -Lunittest++
as well as variations with the I and o flags, but all of them return the same linker errors I get when I try to compile. I've also tried to copy every g++ line in the forums and only get various errors.
I've tried to find a solution in the g++ man pages, read about the flags I've been using and did not infer a solution. I then quickly got buried in quantity of pages in the man entry. The documentation for CodeLite and unittest++ seems woefully out of date, so I posted here on stackoverflow as a last resort.
I'm fairly certain I'm just making a rookie mistake. If someone has feedback, I'd be grateful.

In your explanation, you try to link manually with g++ -c main.cpp -o main.cpp.o -Lunittest++ , but the -L option gives the path to additional directories to search for libraries. You probably want -lunittest++ to link with the unittest++ library. That library should provide the symbols you see in the "undefined reference" errors.
As a side note, "/usr/include" should be in the default search path and there's no need to add it explicitly.

Related

Problems with including custom c++ library in Visual Studio Code

I was trying to include the GMP library, which was simply the code below(I did nothing else):
#include <gmpxx.h>
However, when I tried to compile the code, the following error from g++ compiler occured:
myCode.cpp:3:10: fatal error: gmpxx.h: No such file or directory
#include <gmpxx.h>
^~~~~~~~~~~~~~~~~~~~~~
I have tried everything I searched online, putting the GMP lib here and there, adding INFINITE includepaths in c_cpp_properties.json, still, it keeps showing the message, although, I can find the file through "Go to Definition" option.
Is there any known solution to this?
It's not enough to configure VS Code includes, you need to pass those options to the compiler as well.
You don't mention your platform at all, so I'm going to use an example from my personal machine, a Macbook Pro with the fmt library.
When compiling with the fmt library, I have to provide three more options to the compiler.
-I/usr/local/include // Tells the compiler where to look for extra includes
-L/usr/local/lib // Tells the compiler where to look for extra libraries
-lfmt // fmt-specific command to use fmt library
So the full command ends up looking like this:
g++ -Wall -std=c++17 -I/user/local/include -L/usr/local/lib -lfmt main.cpp
I need all three options because fmt is installed in a non-standard location that the compiler doesn't check by default. According to the documentation, you can get away with just -lgmp and -lgmpxx if you installed the library in a standard location (happens by default with *nix and a package manager, I imagine).
If you use build tasks in VS Code, this can be set up and automated for you.

How to use a dynamic lib in eclipse?

Here is an small example I did with clang++ :
===filename===
calc_mean.cpp
===filename===
===filecontent===
double mean(double a, double b) {
return (a+b) / 2;
}
===filecontent===
===filename===
calc_mean.h
===filename===
===filecontent===
double mean(double, double);
===filecontent===
===filename===
commands.sh
===filename===
===filecontent===
#/usr/bin/env bash
clang++ -c calc_mean.cpp -o calc_mean.o
ar rcs libmean.a calc_mean.o
clang++ -c -fPIC calc_mean.cpp -o calc_mean.o
gcc -shared -W1,-soname,libmean.so.1 -o libmean.so.1.0.1 calc_mean.o
clang++ main.cpp -L. -lmean -o dynamicmain -v
===filecontent===
===filename===
main.cpp
===filename===
===filecontent===
#include <stdio.h>
#include "calc_mean.h"
int main(int argc, char const* argv[])
{
double v1, v2, m;
v1 = 5.0;
v2 = 6.0;
m = mean(v1, v2);
printf("Mean: %f\n", m);
return 0;
}
===filecontent===
It worked perfectly. Now turn to eclipse, I created a project with the dynamic lib generated above in the libs folder:
(source: p.im9.eu)
Adjusted -L and -l settings accordingly:
(source: p.im9.eu)
Got these errors:
(source: p.im9.eu)
Other things I have tried:
(source: p.im9.eu)
(source: p.im9.eu)
The errors stayed the same. I almost want to bang my head against a wall now. Should I start learning cmake already?
update
I added the header file also this time, but eclipse still can't resolve the function mean (through code analysis).
It compiles without an error though, but when I run the output binary, it says:
dyld: Library not loaded: libmean.so
Referenced from: /Users/kaiyin/personal_config_bin_files/workspace/testuselib/Debug/testuselib
Reason: image not found
Edit2:
It hit me that you're on Mac, and I remembered that there's something funny about library loading. So, there are a couple reasons why you'd get Image Not Found. The below still applies, but there's another reason it could be failing. See dyld: Library not loaded: libqscintilla2.5.dylib
I don't know if eclipse on Mac even ships with GCC, or if it's clang only on that platform, but try setting DYLD_LIBRARY_PATH as a quick test to see if it's just Mac Being Special. https://superuser.com/questions/282450/where-do-i-set-dyld-library-path-on-mac-os-x-and-is-it-a-good-idea
Edit:
Yay it compiles! Now we're hitting a linking error. This one is actually pretty fun, and isn't the "common" one I listed below (namely, Unresolved Symbols). This error, "Image Not Found" usually means that the Linker found the library, but could not use it because it was compiled in an incompatible manner.
Why is it in any incompatible format? Welcome to the one feature of C++ that I hate is missing, and one of the reasons pretty much every library out there provides a C interface instead of a C++ interface.
C++ Does Not Provide a stable ABI (Application Binary Interface). This means that libraries compiled with different compilers (or even just different versions of the same compiler may not work together. 99/100 they will just outright refuse to link/work, but even if they do link, you'll get very weird, hard-to-impossible to track down bugs, etc.
Here's the tl;dr: If you want your static lib to be C++ (which i recommend) and have a C++ interface, you need to make sure the exact same version of the compiler is used to compile both your application and the static library. The easiest way to do this is to have eclipse build both the static library and the application.
This is hopefully changing with the next version of C++, as Herb Sutter has put forward a proposal to create a platform defined C++ ABI.
Original:
You need to add the folder containing calc_mean.h to the "Additional Includes" for c++ generation. You can think of include statement as cutting and pasting the contents of the file at that exact line. The error is saying "hey, i went looking for a file called calc_mean.h and couldn't find it." You need to link the library and the header (so main.cpp knows the function)
If it was an error saying "unresolved symbols", with the symbols being in your library, then you would know you've messed up with adding the library or library path (-L).
Cmake is a good tool, but it is nice to know how to use an ide. The basic steps (add library name, add library path, add directory containing library headers) are the same in eclipse, netbeans, visual studio, xcode, etc)

Library not linking/including properly

Alright, I realize that this might seem like a duplicate, but I've tried most variations and attempts via' searched posts, and I'm still coming up with nothing. Here's the issue: I am working with an open-source C library called libxls that is used for reading .xls files (aptly named project.. :) ). The code I'm using is straight off their website, essentially just a beginning toy example to make sure I can access the libraries:Link to their website with the source
#include <stdio.h>
#include "libxls/xls.h"
int main(){
xlsWorkBook* pWB;
pWB = xls_open("Book1.xls", "iso-8859-15//TRANSLIT");
return 0;
}
That's it. Now, the syntax of that is fine. I know for a fact through the nm command that xls_open is indeed available as a function in the .a library, so that's not a problem. in my directory I have the following files (pardon the redundant naming, I was just trying to force it to work real quick):
Book1.xls
libxlsreader.a
libxlsReader.c
libxlsreader.so
Although I don't THINK I need the .so file here since I've tried dynamically linking to where that lives, figured it wasn't a bad plan to try. Alright, so, on the include line, I keep getting the common:
libxlsreader.c:3:37: fatal erro: libxls/xls.h: No such file or directory
Ok fine, so I probably linked in the library wrong, take a look at my compile line arguments:
gcc -o libxlsWrapper libxlsReader.c -L /usr/local/lib/ -lxlsreader -lpthread
huh, well.. that certainly LOOKS right, /usr/local/lib/ is where the library created itself with all of it's .so files, and the .a one in my PWD. Now, I'm a java developer by trade, so I might be missing something blaringly obvious, but for the life of me I can't determine what it is. it certainly seems ok to me.
I'm using GCC (ubuntu/Linaro 4.7.3-lubunutul) 4.7.3 on Linux Mint 15 KDE 32-bit.
If you'd like to reproduce the library for your own testing or problem solving, it can be obtained from
I don't recommend recreating it on windows, I tried for a couple hours yesterday and gave up, so just do the regular ./configure -> make -> make install and that should produce the appropriate libraries for you.
Thanks!
-Will
edit #1: here are some of the other linking attempts I've tried, all with the identical result.
gcc -o libxlsWrapper libxlsReader.c -L. -lxlsreader -I.
gcc -o libxlsWrapper libxlsReader.c -L. -lxlsreader -lpthread
gcc -o libxlsWrapper libxlsReader.c -L. -lxlsreader.so
I also tried a bunch with g++ instead of gcc (throwing darts, I know), same result.
Please do a find your_folder -type f -iname xls.h and then use a gcc -I /the_path to include the path for xls.h. Because the problem you have is that gcc could not locate the header file xls.h.

Undefined reference to MySQL libraries using g++

I am getting undefined reference to 'mysql_suchandsuch##' messages when trying to link my program with the MySQL libraries supplied with the 5.5 server. When MySQL was installed, I used the default path, which for me on Windows is C:\Program Files\MySQL\MySQL Server 5.5\. Originally, I had thought that the spaces are causing my grief, but I think I've correctly worked out how to point to the library path without spaces (still with no luck). If there's another probable cause, please let me know.
I have reviewed a series of questions on this site trying to resolve my issue...
Question 1
Question 2
Question 3
Question 4
Question 5
Question 6
Question 7
Using mingw/g++, I have tried to link using the following options, based on my own research as well as suggestions here:
-L"C:\Program Files\MySQL\MySQL Server 5.5\lib\" -llibmysql.lib
-L"C:\Program Files\MySQL\MySQL Server 5.5\lib\" -lmysqlclient.lib
-L"C:\Progra~1\MySQL\MySQLS~1.5\lib\" -llibmysql.lib
-LC:\Progra~1\MySQL\MySQLS~1.5\lib\ -lmysqlclient.lib
-L"C:\Progra~1\MySQL\MySQLS~1.5\lib\" -lmysql
In all cases, I have put the -L/-l options at the right-most part of the statement, as I understand this can matter.
I have confirmed the libraries do exist. In the /lib dir, I have libmysql.lib, mysqlclient.lib, and libmysql.dll. I have not tried to link with the .dll, as no tutorial/forum I've reviewed suggested that.
I am not using MAKEFILES.
Does anyone have specific experience with g++/MySQL?
The following commands work fine for me using a GCC 4.6.1 from November 2011:
g++ my.cpp -I D:\Opt\MySQL5.5\include ^
D:\Opt\MySQL5.5\lib\libmysql.dll -o myWithDll.exe
g++ my.cpp -I D:\Opt\MySQL5.5\include ^
-L D:\Opt\MySQL5.5\lib -lmysql -o myWithLib.exe
So both linking against the LIB and the DLL do work.
You may get a warning (see Gaffi's comment). This is because the linker does fuzzy linking for you without you having it specified; normally, it would have failed to link. It is being nice, though, and making it work for you, at the same time warning you about things happening without your having requested them. The way to suppress the warning is to make fuzzy linking explicit:
g++ -Wl,--enable-stdcall-fixup my.cpp -I D:\Opt\MySQL5.5\include ^
D:\Opt\MySQL5.5\lib\libmysql.dll -o myWithDll.exe
g++ -Wl,--enable-stdcall-fixup my.cpp -I D:\Opt\MySQL5.5\include ^
-L D:\Opt\MySQL5.5\lib -lmysql -o myWithLib.exe
This is a Cygwin/RedHat/MinGW extension to the linker; the docs are here:
--enable-stdcall-fixup
--disable-stdcall-fixup
If the link[er] finds a symbol that it cannot resolve, it will attempt to
do “fuzzy linking” by looking for another defined symbol that differs
only in the format of the symbol name (cdecl vs stdcall) and will
resolve that symbol by linking to the match. For example, the
undefined symbol _foo might be linked to the function _foo#12, or the
undefined symbol _bar#16 might be linked to the function _bar. When
the linker does this, it prints a warning, since it normally should
have failed to link, but sometimes import libraries generated from
third-party dlls may need this feature to be usable. If you specify
--enable-stdcall-fixup, this feature is fully enabled and warnings
are not printed. If you specify --disable-stdcall-fixup, this feature is
disabled and such mismatches are considered to be errors. [This option
is specific to the i386 PE targeted port of the linker]
did you try -lmysql as the linker automatically prepends lib and appends .lib

Undefined symbol _main when trying to build logstalgia on mac

I have been trying to build the logstalgia project (http://code.google.com/p/logstalgia/) on my Mac (10.5). Rather than having to link it to the system libraries correctly, I have built and added all of the dependencies to the project. I am new at this, but I do think I have done this correctly, mostly because I have had two of my friends who are much more experienced say so.
Adding the frameworks removed all of the compile errors, but I still get a linker error. It seems to not be able to find the main() function. I have verified I included main.cpp in the sources to be compiled (using XCode) and that there are no accidental double declarations. I have also verified that the main function is correctly declared (no missing brackets, etc).
It is as though XCode does not link in the correct order. Any help would be really appreciated, I am really excited to be down to a single error! (Hope fixing this does not open a floodgate).
Thanks,
Hamilton
PS - I can definitely provide a zip of the Xcode project if anyone is willing to look!
Checking Dependencies
Ld "/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Debug/Untitled" normal i386
cd "/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled"
setenv MACOSX_DEPLOYMENT_TARGET 10.5
/developer/usr/bin/g++-4.0 -arch i386 -isysroot /developer/SDKs/MacOSX10.5.sdk "-L/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Debug" -L/sw/lib "-L/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/../../pcre-7.9/.libs" -L/opt/local/lib -L/sw/lib "-F/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Debug" -F/Users/hamiltont/Downloads/logstalgia-0.9.2 -F2/src/SDL.framework "-F/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled" -filelist "/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Untitled.build/Debug/Untitled.build/Objects-normal/i386/Untitled.LinkFileList" -mmacosx-version-min=10.5 -framework OpenGL -lpcre -lSDL -lSDL_image-1.2.0 -prebind -o "/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Debug/Untitled"
Undefined symbols:
"_main", referenced from:
start in crt1.10.5.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
I got this error to go away. If I understand, essentially SDL re-names the main function, so that it can do some stuff, then run your application, then clean up. Turns out that if you are building in Xcode, you must use ObjectiveC to compile your application.
In Xcode, telling the linker to try and use SDL_main(), rather than just main() does not work (for some technical reasons that are a bit beyond me). So, you include a few Objective C files. In Oc, you get the benefit of being able to say explicitely what the name of your main class is. Hence, the Objective C files you include seem to do nothing more than let Xcode know to look for SDL_main().
In summary, this really had nothing to do with Logstalgia, but was entirely a problem with getting SDL to link correctly in Xcode. This link is talking about this problem exactly. The SDLMain.h and SDLMain.m are Objective C files. If you can't find them, try googleing "Setting up SDL templates in Xcode." I installed the templates in Xcode, used one of them to create an empty project that would compile, link, and run (and promptly do nothing!) and then I added the project files I wanted to the pre-configured project.
Thanks!
Double-check the link file list to make sure main.cpp's object file is present there:
/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Untitled.build/Debug/Untitled.build/Objects-normal/i386/Untitled.LinkFileList
You might also want to preprocess the main.cpp to make sure main isn't getting inadvertently renamed (via a rogue macro) or omitted (via a rogue #if).