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.
Related
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.
I'm trying to build headless blackcoin from source on Windows 8 with mingw 6.3
and I got the following error: .../src/leveldb/libleveldb.a(env_win.o):env_win.cc:(.text+0xaff): undefined reference to '_imp__PathFileExistsW#4'
This function is mentioned here https://msdn.microsoft.com/en-us/library/windows/desktop/bb773584(v=vs.85).aspx
I would appreciate if someone can help me.
P.S. I linked the appropriate library.
Finally I was able to build it. Probably it is obvious for thoose guys who down voted the question. I simply answer since it might save time to somebody.
I relied on the Makefile which is a part of the project source code. Required library (shlwapi) present in the file so I was confused when it failed to build. Everything went well when I placed the library at the end of the linked files.
It was something like this
g++ ... -o -lshlwapi... /src/leveldb/libleveldb.a /src/leveldb/libmemenv.a
And became this
g++ ... -o /src/leveldb/libleveldb.a /src/leveldb/libmemenv.a -lshlwapi
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.
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)
I'm trying to create a program that uses some of the code from WebKit/GTK+. Specifically, I want to load a string, use WebKit's parser to construct a DOM tree and then iterate over that tree.
I'm trying to use a class called HTMLDocument. WebKit/GTK+ doesn't expose this as part of its API and I'm running into some trouble linking against it.
I'm able to build WebKit/GTK+ normally, which gives me a file called: libwebkit-1.0.so. My program is:
#include <iostream>
#include <WebCore/config.h>
#include <WebCore/html/HTMLDocument.h>
using namespace WebCore;
int main() {
String title = "test";
RefPtr<HTMLDocument> d = HTMLDocument::create(0);
d->open();
d->write("<!doctype html><html><head><title>" + title + "</title></head><body></body></html>");
}
This compiles fine (I'm using the same include directives used by webkit to build), but results in linking errors.
...test_doc.cpp:18: undefined reference to `WebCore::String::String(char const*)'
...test_doc.cpp:21: undefined reference to WebCore::Document::open(WebCore::Document*)'
...(similar for every function I use)
If I run:
nm -C .libs/libwebkit-1.0.so | grep 'WebCore::Document::open'
I see:
003b1830 T WebCore::Document::open(WebCore::Document*)
which seems to indicate that the function is available. I have a reasonable amount of C++ experience, but not much experience with linking files under Linux.
I'm not expecting this exact problem to be solved, but I'm hoping someone can correct me if I have conceptual problems. My main question is why I see "undefined reference" errors when I'm linking with an .so file that lists that function as being defined. Is another file or build step needed?
Thank you very much.
Using:
Ubuntu 9.10
g++ 4.4.1
g++ is invoked with:
g++ --debug -DHAVE_CONFIG_H -I. `pkg-config --cflags libsoup-2.4` \
-DBUILDING_CAIRO__=1 -DBUILDING_GTK__=1 -DWTF_CHANGES -DWTF_USE_ICU_UNICODE=1 \
-DNDEBUG -I./WebCore -I./WebCore/accessibility -I./WebCore/bindings/js \
-I./WebCore/bridge -I./WebCore/bridge/c -I./WebCore/css -I./WebCore/dom \
...many more webkit include directories...
-DDATA_DIR=\"/usr/local/share\" \
test_doc.cpp -o test_doc.out \
./webkit-1.1.15.3/.libs/libwebkit-1.0.so
(I get the same result with -L/path/to/lib -lwebkit-1.0)
I think you might be running into an ordering problem: man g++ specifies that the order of the -l option is significant, and from memory the linker will only look for symbols in objects which have preceeded the current file on the command line.
I suspect what is happening is that the linker is trying to link test_doc before it's seen libwebkit-1.0.so, so it hasn't seen any of those symbols yet and bails.
You should use the -L/path/to/web and -lwebkit-1.0.
Also, I would compile your .cpp file in to a .o and then build your executable separately to make sure things are isolated.
Anyway, you may need to set your $LD_LIBRARY_PATH environment variable to include the path where that .so is stored. If you link to a shared library, you will need that library at run-time. Therefore, you do not want to have your webkit SO stored in its build directory (build/.libs). You want to install it. If you are not root, then you should ./configure with a --prefix=/some/path to install it to some local directory. Alternatively, you can link against the static library. One way to do this is to use the -bstatic (or similar) flag before your -lwebkit-1.0.
This is a good resource for Linux library creation and use.
I think you're issue is that the symbols you need are not exported. You can do objdump --dynamic-syms libwebkit-1.0.so to see which symbols are available. In the WebKit GTK build files there is use of the -fvisibility=hidden flag to restrict the symbols. Check your generated GNUMakefile and you'll see SYMBOL_VISIBILITY = -fvisibility=hidden. You should be able to modify the build files to get what you need.