I am trying to build some code that uses the EVP_* functions in Ubuntu, however when I build, I get the dreaded "undefined reference" errors.
I am using Ubuntu 11.10.
The following line is how I compile:
g++ -lcrypto -lssl *.cpp -o IOService
[...]
crypto.cpp:(.text+0x8): undefined reference to `EVP_md5'
[...]
The cpp files include openssl/evp.h.
I have installed the libssl1.0.0-dbg package, but those libraries get installed in /usr/lib/debug/lib/i386-linux-gnu/ where my linker doesn't seem to find them. I tried softlinking and copying the .so files, to no avail (and I have the feeling this is not the way to go).
ld is a one-pass linker, meaning that you have to add libraries after the object files that use them: g++ *.cpp -o IOService -lcrypto (I think libssl is not needed if all you need is md5)
Related
I'm trying to compile a program on Ubuntu 11.10 that uses the Boost libraries. I have the 1.46-dev Boost libraries from the Ubuntu Repository installed, but I get an error when compiling the program.
undefined reference to boost::system::system_category()
What is it that I do wrong?
The boost library you are using depends on the boost_system library. (Not all of them do.)
Assuming you use gcc, try adding -lboost_system to your compiler command line in order to link against that library.
Linking with a library that defines the missing symbol (-lboost_system) is the obvious solution, but in the particular case of Boost.System, a misfeature in the original design makes it use boost::system::generic_category() and boost::system::system_category() needlessly. Compiling with the flag -DBOOST_SYSTEM_NO_DEPRECATED disables that code and lets a number of programs compile without requiring -lboost_system (that link is of course still needed if you explicitly use some of the library's features).
Starting from Boost 1.66 and this commit, this behavior is now the default, so hopefully fewer and fewer users should need this answer.
As noticed by #AndrewMarshall, an alternative is to define BOOST_ERROR_CODE_HEADER_ONLY which enables a header-only version of the code. This was discouraged by Boost as it can break some functionality. However, since 1.69, header-only seems to have become the default, supposedly making this question obsolete.
Another workaround for those who don't need the entire shebang: use the switch
-DBOOST_ERROR_CODE_HEADER_ONLY.
If you use CMake, it's add_definitions(-DBOOST_ERROR_CODE_HEADER_ONLY).
The above error is a linker error... the linker a program that takes one or more objects generated by a compiler and combines them into a single executable program.
You must add -lboost_system to you linker flags which indicates to the linker that it must look for symbols like boost::system::system_category() in the library libboost_system.so.
If you have main.cpp, either:
g++ main.cpp -o main -lboost_system
OR
g++ -c -o main.o main.cpp
g++ main.o -lboost_system
When using CMAKE and find_package, make sure it is :
find_package(Boost COMPONENTS system ...)
and not
find_package(boost COMPONENTS system ...)
Some people may have lost hours for that ...
I got the same Problem:
g++ -mconsole -Wl,--export-all-symbols -LC:/Programme/CPP-Entwicklung/MinGW-4.5.2/lib -LD:/bfs_ENTW_deb/lib -static-libgcc -static-libstdc++ -LC:/Programme/CPP-Entwicklung/boost_1_47_0/stage/lib \
D:/bfs_ENTW_deb/obj/test/main_filesystem.obj \
-o D:/bfs_ENTW_deb/bin/filesystem.exe -lboost_system-mgw45-mt-1_47 -lboost_filesystem-mgw45-mt-1_47
D:/bfs_ENTW_deb/obj/test/main_filesystem.obj:main_filesystem.cpp:(.text+0x54):
undefined reference to `boost::system::generic_category()
Solution was to use the debug-version of the system-lib:
g++ -mconsole -Wl,--export-all-symbols -LC:/Programme/CPP-Entwicklung/MinGW-4.5.2/lib -LD:/bfs_ENTW_deb/lib -static-libgcc -static-libstdc++ -LC:/Programme/CPP-Entwicklung/boost_1_47_0/stage/lib \
D:/bfs_ENTW_deb/obj/test/main_filesystem.obj \
-o D:/bfs_ENTW_deb/bin/filesystem.exe -lboost_system-mgw45-mt-d-1_47 -lboost_filesystem-mgw45-mt-1_47
But why?
When I had this, problem, the cause was the ordering of the libraries. To fix it, I put libboost_system last:
g++ mingw/timer1.o -o mingw/timer1.exe -L/usr/local/boost_1_61_0/stage/lib \
-lboost_timer-mgw53-mt-1_61 \
-lboost_chrono-mgw53-mt-1_61 \
-lboost_system-mgw53-mt-1_61
This was on mingw with gcc 5.3 and boost 1.61.0 with a simple timer example.
in my case, adding -lboost_system was not enough, it still could not find it in my custom build environment. I had to use the advice at Get rid of "gcc - /usr/bin/ld: warning lib not found" and change my ./configure command to:
./configure CXXFLAGS="-I$HOME/include" LDFLAGS="-L$HOME/lib -Wl,-rpath-link,$HOME/lib" --with-boost-libdir=$HOME/lib --prefix=$HOME
for more details see Boost 1.51 : "error: could not link against boost_thread !"
...and in case you wanted to link your main statically, in your Jamfile add the following to requirements:
<link>static
<library>/boost/system//boost_system
and perhaps also:
<linkflags>-static-libgcc
<linkflags>-static-libstdc++
I'm trying to compile a program on Ubuntu 11.10 that uses the Boost libraries. I have the 1.46-dev Boost libraries from the Ubuntu Repository installed, but I get an error when compiling the program.
undefined reference to boost::system::system_category()
What is it that I do wrong?
The boost library you are using depends on the boost_system library. (Not all of them do.)
Assuming you use gcc, try adding -lboost_system to your compiler command line in order to link against that library.
Linking with a library that defines the missing symbol (-lboost_system) is the obvious solution, but in the particular case of Boost.System, a misfeature in the original design makes it use boost::system::generic_category() and boost::system::system_category() needlessly. Compiling with the flag -DBOOST_SYSTEM_NO_DEPRECATED disables that code and lets a number of programs compile without requiring -lboost_system (that link is of course still needed if you explicitly use some of the library's features).
Starting from Boost 1.66 and this commit, this behavior is now the default, so hopefully fewer and fewer users should need this answer.
As noticed by #AndrewMarshall, an alternative is to define BOOST_ERROR_CODE_HEADER_ONLY which enables a header-only version of the code. This was discouraged by Boost as it can break some functionality. However, since 1.69, header-only seems to have become the default, supposedly making this question obsolete.
Another workaround for those who don't need the entire shebang: use the switch
-DBOOST_ERROR_CODE_HEADER_ONLY.
If you use CMake, it's add_definitions(-DBOOST_ERROR_CODE_HEADER_ONLY).
The above error is a linker error... the linker a program that takes one or more objects generated by a compiler and combines them into a single executable program.
You must add -lboost_system to you linker flags which indicates to the linker that it must look for symbols like boost::system::system_category() in the library libboost_system.so.
If you have main.cpp, either:
g++ main.cpp -o main -lboost_system
OR
g++ -c -o main.o main.cpp
g++ main.o -lboost_system
When using CMAKE and find_package, make sure it is :
find_package(Boost COMPONENTS system ...)
and not
find_package(boost COMPONENTS system ...)
Some people may have lost hours for that ...
I got the same Problem:
g++ -mconsole -Wl,--export-all-symbols -LC:/Programme/CPP-Entwicklung/MinGW-4.5.2/lib -LD:/bfs_ENTW_deb/lib -static-libgcc -static-libstdc++ -LC:/Programme/CPP-Entwicklung/boost_1_47_0/stage/lib \
D:/bfs_ENTW_deb/obj/test/main_filesystem.obj \
-o D:/bfs_ENTW_deb/bin/filesystem.exe -lboost_system-mgw45-mt-1_47 -lboost_filesystem-mgw45-mt-1_47
D:/bfs_ENTW_deb/obj/test/main_filesystem.obj:main_filesystem.cpp:(.text+0x54):
undefined reference to `boost::system::generic_category()
Solution was to use the debug-version of the system-lib:
g++ -mconsole -Wl,--export-all-symbols -LC:/Programme/CPP-Entwicklung/MinGW-4.5.2/lib -LD:/bfs_ENTW_deb/lib -static-libgcc -static-libstdc++ -LC:/Programme/CPP-Entwicklung/boost_1_47_0/stage/lib \
D:/bfs_ENTW_deb/obj/test/main_filesystem.obj \
-o D:/bfs_ENTW_deb/bin/filesystem.exe -lboost_system-mgw45-mt-d-1_47 -lboost_filesystem-mgw45-mt-1_47
But why?
When I had this, problem, the cause was the ordering of the libraries. To fix it, I put libboost_system last:
g++ mingw/timer1.o -o mingw/timer1.exe -L/usr/local/boost_1_61_0/stage/lib \
-lboost_timer-mgw53-mt-1_61 \
-lboost_chrono-mgw53-mt-1_61 \
-lboost_system-mgw53-mt-1_61
This was on mingw with gcc 5.3 and boost 1.61.0 with a simple timer example.
in my case, adding -lboost_system was not enough, it still could not find it in my custom build environment. I had to use the advice at Get rid of "gcc - /usr/bin/ld: warning lib not found" and change my ./configure command to:
./configure CXXFLAGS="-I$HOME/include" LDFLAGS="-L$HOME/lib -Wl,-rpath-link,$HOME/lib" --with-boost-libdir=$HOME/lib --prefix=$HOME
for more details see Boost 1.51 : "error: could not link against boost_thread !"
...and in case you wanted to link your main statically, in your Jamfile add the following to requirements:
<link>static
<library>/boost/system//boost_system
and perhaps also:
<linkflags>-static-libgcc
<linkflags>-static-libstdc++
I've been working on this for a while now, and can't seem to make sense of the situation - partly bceause I don't fully understand what's going on (which is why I came here).
I'm doing a sort of boost hello world as follows:
#include <boost/thread/thread.hpp>
#include <cstdio>
void helloworld() {
std::printf("HELLO FROM A BOOST THREAD!");
}
int main(int argc, char **argv) {
boost::thread t(&helloworld);
t.join();
}
This is on Windows. I stored the Boost directory in C:\Boost. I ran bootstrap and bjam, and now have a stage/lib folder that contains all the .lib files. The lib files relating to the boost/thread library are:
libboost_thread-vc100-mt.lib
libboost_thread-vc100-mt-1_46_1.lib
libboost_thread-vc100-mt-gd.lib
libboost_thread-vc100-mt-gd-1_46_1.lib
Now I compile:
g++ -c main.cpp -I/Boost
that line works fine, I get main.o. Then:
g++ -o test.exe main.o -L/Boost/stage/lib -llibboost_thread-vc100-mt
And that's where the trouble happens. First of all, If I didn't type the -l argument the way I did, MinGW couldn't even find the file. Meaning, if I tried:
-lboost_thread-vc100-mt
instead of the way I typed it above (and how I thought it should be done), ld would exit with no such file. Anyway, this is now the output I'm getting from that line:
main.o:main.cpp:(.text+0x47): undefined reference to `_imp___ZN5boost6thread4joinEv'
main.o:main.cpp:(.text+0x55): undefined reference to `_imp___ZN5boost6threadD1Ev'
main.o:main.cpp:(.text+0x70): undefined reference to `_imp___ZN5boost6threadD1Ev'
main.o:main.cpp:(.text$_ZN5boost6threadC1IPFvvEEET_NS_10disable_ifINS_14is_convertibleIRS4_NS_6detail13thread_move_tIS4_EEEEPNS0_5dummyEE4typeE[boost::thread::thread<void (*)()>(void (*)(), boost::disable_if<boost::is_convertible<void (*&)(), boost::detail::thread_move_t<void (*)()> >, boost::thread::dummy*>::type)]+0x23): undefined reference to `_imp___ZN5boost6thread12start_threadEv'
collect2: ld returned 1 exit status
Now somewhere in there, I can tell that these are apparently the functions I'm supposed to be getting from boost/thread, and apparently it does find the lib file, so why isn't it linking correctly?
Thank you very much for any help!
EDIT:
I've rebuilt boost using the bjam "stage" option
bjam toolset=gcc stage
Now, after the build completes, I'm left with a stage/lib folder with .a files, as is to be expected. These are the boost/thread related libraries:
libboost_thread-mgw45-mt-1_46_1.a
libboost_thread-mgw45-mt-d-1_46_1.a
However, linking as follows:
g++ -o test.exe main.o -L/Boost/stage/lib -lboost_thread-mgw45-mt-1_46_1
outputs the exact same errors. Also tried:
g++ -o test.exe main.o -L/Boost/stage/lib -lboost_thread-mgw45-mt-1_46_1 -static
I'm at a loss, still.
Solved the problem. Boost's headers are configured to be dynamically linked, but the dynamic libraries (dll's) are not built unless you specify:
--build-type=complete
when invoking bjam. After that, copy the appropriate dll to your application directory, but still use the
-L/BOOST_DIR/stage/lib -lname
when linking.
This set of library files:
libboost_thread-vc100-mt.lib
libboost_thread-vc100-mt-1_46_1.lib
libboost_thread-vc100-mt-gd.lib
libboost_thread-vc100-mt-gd-1_46_1.lib
are for the Visual Studio 2010 compiler. They won't work with GCC. If you want to use gcc/MinGW, you'll need to download/build a set of boost libraries for that compiler. Alternatively you can install VS 2010 and use that compiler (the free VC++ 2010 Express version should work fine if cost is an issue).
You can get a MinGW distribution with Boost already in the package from http://nuwen.net/mingw.html (32-bit target only, I believe).
To answer about getting the errors with using the MinGW libs:
The _imp_ prefixes on the symbols is an indication that g++ is looking to link to a a dll/shared library. The .lib file you have are for static libraries (which is what also what I get when doing a straightforward bjam build of the libraries). If you look in boost/thread/detail/config.hpp you'll see that for Win32 builds it defaults to building against a DLL library unless the MSVC or Intel compiler is being used.
I'm not even sure exactly how to build the DLL libraries - I'll have to look it up. In the meantime, you can use the following command to build your example such that it'll link against the static library. The BOOST_THREAD_USE_LIB macro build the .cpp file such that it'll expect to link against the static library:
g++ -I/Boost -DBOOST_THREAD_USE_LIB -c main.cpp
I need to use libcurl in a piece of software I am writing on my ubuntu machine. I am using Eclipse to write and compile all of the software. When I put the libcurl files in the same folder as the .cpp file, and include the curl.h file in the header, When I attempt to compile the program, It comes up with these errors:
Building target: sms
Invoking: GCC C++ Linker
g++ -o"sms" ./src/sms.o
./src/sms.o: In function `main':
/home/geekman/workspace/sms/Debug/../src/sms.cpp:38: undefined reference to `curl_easy_init'
/home/geekman/workspace/sms/Debug/../src/sms.cpp:42: undefined reference to `curl_easy_setopt'
/home/geekman/workspace/sms/Debug/../src/sms.cpp:44: undefined reference to `curl_easy_setopt'
/home/geekman/workspace/sms/Debug/../src/sms.cpp:46: undefined reference to `curl_easy_perform'
/home/geekman/workspace/sms/Debug/../src/sms.cpp:47: undefined reference to `curl_easy_cleanup'
collect2: ld returned 1 exit status
make: *** [sms] Error 1
I took the contents of the include folder from libcurl, and placed them in the same folder as the .cpp file. then in the header of the .cpp file, I typed:
#include <curl/curl.h>
I also tried:
#include "curl/curl.h"
Any ideas on the problem? Thanks.
Your header file inclusions are just fine; your problem is occurring at the linking step. In order to link against libcurl, you need to add the -lcurl command line option, assuming it's installed in a standard directory:
g++ -o sms ./src/sms.o -lcurl
If it's not installed in a standard directory, you also need to add the -L/path/to/libcurl, e.g. something like:
# Assuming that /home/geekman/workspace/libcurl is where libcurl.a is located
g++ -o sms ./src/sms.o -L/home/geekman/workspace/libcurl -lcurl
Also note that the -lcurl option has to appear after the list of object files you're linking, otherwise it won't link properly.
You can try to use curl-config --libs.
An alternate answer (the first one is excellent). Consider using the output returned by "pkg-config --libs libcurl" as an argument to your compiler.
For example,
CPPFLAGS=`pkg-config --libs libcurl`
g++ $CPPFLAGS myfile.o
Pkg-config is a standard way for open source libraries to communicate to you how to link against them / #include their files.
Anyone who is using ecplise CDT then you need to do following. First on terminal enter
curl-config --libs
On my machine, the result is
-L/usr/lib/i386-linux-gnu -lcurl
then do according to this screenshot and you will be able to compile. btw don't forget to add header files in your code
So you enter library folder path without -L and library name without -l because they will be automatically added by linker.
You have to link the library to your program. With gcc (and most other compilers) you can specify the libraries to link with -lname_wo_lib, e.g. -lcurl
Also see GNU GCC Manual - Options for Linking for a detailed explanation of the options Adam Rosenfield said. For standard search directories, see An Introduction to GCC - for the GNU Compilers gcc and g++ - Setting Search Paths.
In addition to the first answer, I had to link the curlpp library too. So to compile the main.cpp file which included the curlpp I had to do:
g++ main.cpp -lcurl -lcurlpp
Using only one of the two links would return different errors regarding different links. It is important to remind that this only worked because I had installed all the necessary libraries in the standard include folders
I would like to utilize the UnitTest++ library in a testing file. However, I am having some difficulty getting the library to be included at compile time. So here is my current directory structure:
tests/
UnitTests++/
libUnitTest++.a
src/
UnitTests++.h
unit/
test.cpp
I have just used the UnitTest++ getting started guide to just get the library setup. Here is test.cpp:
// test.cpp
#include <UnitTest++.h>
TEST(FailSpectacularly)
{
CHECK(false);
}
int main()
{
return UnitTest::RunAllTests();
}
And I am currently trying to compile with:
gcc -lUnitTest++ -L../UnitTest++/ -I../UnitTest++/src/ test.cpp
I am currently getting a bunch output with ld: symbol(s) not found at the end. So how would I be able to get the UnitTest++ library properly included when this program is compiled? I am on a Mac and I'd also like for there to be an easy way for people on a Linux machine to run these same tests.
Whew, I hope this provides enough information, if not please let me know.
I was able to build it in the following manner
gcc -L../UnitTest++/ -I../UnitTest++/src/ test.cpp -lUnitTest++ -lstdc++
or
g++ -L../UnitTest++/ -I../UnitTest++/src/ test.cpp -lUnitTest++
that links to libstdc++ automatically.
GCC documentation says:
-llibrary
-l library
Search the library named library when linking. (The second alternative with the library as a separate argument is only for POSIX compliance and is not recommended.)
It makes a difference where in the command you write this option; the linker searches and processes libraries and object files in the order they are specified.
Thus, foo.o -lz bar.o' searches libraryz' after file foo.o but before bar.o. If bar.o refers to functions in `z', those functions may not be loaded.
I guess that's why the library symbols are not found when you first specify -lUnitTest++ and then test.cpp
Compile test.cpp to get test.o
and use
g++ test.o libUnitTest++.a -o ./exectest
to get the ./exectest executable
libUnitTest++.a is just an archive of all the object files of UnitTest++. You just need to link all the object files (your test object file + libUnitTest++.a)
Try editing the makefile that came with unittest++ and make it suitable for your case
The message ld: symbol(s) not found means you haven't compiled the library. So you need to go in the UnitTest++ folder, compile and install it.
I've never worked on a MAC, but in linux, libraries are usually compiled and installed with:
./configure
make
make install
In the UnitTest++ link you posted, you should simply:
make install
Then you will have the UnitTest++.so library in the libraries folder of your OS. Now the library can be linked with your program with the -lUnitTest++ command.
Usually you have to put -Lsomething before the -lsomething that requires it.