Compile error when including boost/thread.hpp - c++

Question

I'm trying to use threads in C++, using boost's thread library. Clang is giving me an error and I don't know how to interpret it. The file I'm trying to compile is about as minimal as it can get:
#include <iostream>
#include <boost/thread.hpp>
using namespace std;
int main() {
return 0;
}
Here's the transcript:
$ clang++ -std=c++11 -o 4.4 4.4.cpp -v
Apple clang version 4.1 (tags/Apple/clang-421.11.66) (based on LLVM 3.1svn)
Target: x86_64-apple-darwin12.2.1
Thread model: posix
"/usr/bin/clang" -cc1 -triple x86_64-apple-macosx10.8.0 -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -main-file-name 4.4.cpp -pic-level 1 -mdisable-fp-elim -relaxed-aliasing -masm-verbose -munwind-tables -target-cpu core2 -target-linker-version 134.9 -v -resource-dir /usr/bin/../lib/clang/4.1 -fmodule-cache-path /var/folders/mt/k4dhhm7d7_7_q6drl3zkjj4r0000gn/T/clang-module-cache -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /Users/thinkpad20/Documents/workspace/cpp/homework4 -ferror-limit 19 -fmessage-length 100 -stack-protector 1 -mstackrealign -fblocks -fobjc-runtime-has-arc -fobjc-runtime-has-weak -fobjc-dispatch-method=mixed -fobjc-default-synthesize-properties -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o /var/folders/mt/k4dhhm7d7_7_q6drl3zkjj4r0000gn/T/4-49j8fE.o -x c++ 4.4.cpp
clang -cc1 version 4.1 based upon LLVM 3.1svn default target x86_64-apple-darwin12.2.1
ignoring nonexistent directory "/usr/include/c++/4.2.1/i686-apple-darwin10/x86_64"
ignoring nonexistent directory "/usr/include/c++/4.0.0"
ignoring nonexistent directory "/usr/include/c++/4.0.0/i686-apple-darwin8/"
ignoring nonexistent directory "/usr/include/c++/4.0.0/backward"
ignoring nonexistent directory "/usr/local/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/include/c++/4.2.1
/usr/include/c++/4.2.1/backward
/usr/bin/../lib/clang/4.1/include
/usr/include
/System/Library/Frameworks (framework directory)
/Library/Frameworks (framework directory)
End of search list.
"/usr/bin/ld" -demangle -dynamic -arch x86_64 -macosx_version_min 10.8.0 -o 4.4 /var/folders/mt/k4dhhm7d7_7_q6drl3zkjj4r0000gn/T/4-49j8fE.o -lstdc++ -lSystem /usr/bin/../lib/clang/4.1/lib/darwin/libclang_rt.osx.a
Undefined symbols for architecture x86_64:
"boost::system::system_category()", referenced from:
___cxx_global_var_init3 in 4-49j8fE.o
"boost::system::generic_category()", referenced from:
___cxx_global_var_init1 in 4-49j8fE.o
___cxx_global_var_init2 in 4-49j8fE.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Any help is appreciated! :)

Answer 1

You need to tell clang which libraries to link against. In your case, this is boost_system (that's what the error message tells you) and (as soon as you actually get around to using some threading stuff in your program) boost_thread as well, so compile it like this:
clang++ -std=c++11 -o myapp myfile.cpp -lboost_system -lboost_thread