问题
OSX 10.11.3 (El Capitan)
I'm getting link errors while building the first example from the Boost::Log tutorial.
#include <boost/log/trivial.hpp>
int main(int, char*[])
{
BOOST_LOG_TRIVIAL(trace) << "A trace severity message";
BOOST_LOG_TRIVIAL(debug) << "A debug severity message";
BOOST_LOG_TRIVIAL(info) << "An informational severity message";
BOOST_LOG_TRIVIAL(warning) << "A warning severity message";
BOOST_LOG_TRIVIAL(error) << "An error severity message";
BOOST_LOG_TRIVIAL(fatal) << "A fatal severity message";
return 0;
}
Here are the diagnostics:
$ c++ trivial_log_test.cpp
Undefined symbols for architecture x86_64:
"boost::log::v2s_mt_posix::record_view::public_data::destroy(boost::log::v2s_mt_posix::record_view::public_data const*)", referenced from:
boost::log::v2s_mt_posix::record::reset() in trivial_log_test-6968b8.o
"boost::log::v2s_mt_posix::aux::stream_provider<char>::release_compound(boost::log::v2s_mt_posix::aux::stream_provider<char>::stream_compound*)", referenced from:
boost::log::v2s_mt_posix::aux::record_pump<boost::log::v2s_mt_posix::sources::severity_logger_mt<boost::log::v2s_mt_posix::trivial::severity_level> >::auto_release::~auto_release() in trivial_log_test-6968b8.o
"boost::log::v2s_mt_posix::aux::stream_provider<char>::allocate_compound(boost::log::v2s_mt_posix::record&)", referenced from:
boost::log::v2s_mt_posix::aux::record_pump<boost::log::v2s_mt_posix::sources::severity_logger_mt<boost::log::v2s_mt_posix::trivial::severity_level> >::record_pump(boost::log::v2s_mt_posix::sources::severity_logger_mt<boost::log::v2s_mt_posix::trivial::severity_level>&, boost::log::v2s_mt_posix::record&) in trivial_log_test-6968b8.o
"boost::log::v2s_mt_posix::aux::unhandled_exception_count()", referenced from:
boost::log::v2s_mt_posix::aux::record_pump<boost::log::v2s_mt_posix::sources::severity_logger_mt<boost::log::v2s_mt_posix::trivial::severity_level> >::record_pump(boost::log::v2s_mt_posix::sources::severity_logger_mt<boost::log::v2s_mt_posix::trivial::severity_level>&, boost::log::v2s_mt_posix::record&) in trivial_log_test-6968b8.o
boost::log::v2s_mt_posix::aux::record_pump<boost::log::v2s_mt_posix::sources::severity_logger_mt<boost::log::v2s_mt_posix::trivial::severity_level> >::~record_pump() in trivial_log_test-6968b8.o
"boost::log::v2s_mt_posix::core::open_record(boost::log::v2s_mt_posix::attribute_set const&)", referenced from:
boost::log::v2s_mt_posix::record boost::log::v2s_mt_posix::sources::basic_logger<char, boost::log::v2s_mt_posix::sources::severity_logger_mt<boost::log::v2s_mt_posix::trivial::severity_level>, boost::log::v2s_mt_posix::sources::multi_thread_model<boost::log::v2s_mt_posix::aux::light_rw_mutex> >::open_record_unlocked<boost::parameter::aux::tagged_argument<boost::log::v2s_mt_posix::keywords::tag::severity, boost::log::v2s_mt_posix::trivial::severity_level const> >(boost::parameter::aux::tagged_argument<boost::log::v2s_mt_posix::keywords::tag::severity, boost::log::v2s_mt_posix::trivial::severity_level const> const&) in trivial_log_test-6968b8.o
"boost::log::v2s_mt_posix::core::push_record_move(boost::log::v2s_mt_posix::record&)", referenced from:
boost::log::v2s_mt_posix::sources::basic_logger<char, boost::log::v2s_mt_posix::sources::severity_logger_mt<boost::log::v2s_mt_posix::trivial::severity_level>, boost::log::v2s_mt_posix::sources::multi_thread_model<boost::log::v2s_mt_posix::aux::light_rw_mutex> >::push_record_unlocked(boost::rv<boost::log::v2s_mt_posix::record>&) in trivial_log_test-6968b8.o
"boost::log::v2s_mt_posix::sources::aux::get_severity_level()", referenced from:
boost::log::v2s_mt_posix::sources::aux::severity_level<boost::log::v2s_mt_posix::trivial::severity_level>::set_value(boost::log::v2s_mt_posix::trivial::severity_level) in trivial_log_test-6968b8.o
"boost::log::v2s_mt_posix::trivial::logger::get()", referenced from:
_main in trivial_log_test-6968b8.o
"boost::log::v2s_mt_posix::core::get_logging_enabled() const", referenced from:
boost::log::v2s_mt_posix::record boost::log::v2s_mt_posix::sources::basic_composite_logger<char, boost::log::v2s_mt_posix::sources::severity_logger_mt<boost::log::v2s_mt_posix::trivial::severity_level>, boost::log::v2s_mt_posix::sources::multi_thread_model<boost::log::v2s_mt_posix::aux::light_rw_mutex>, boost::log::v2s_mt_posix::sources::features<boost::log::v2s_mt_posix::sources::severity<boost::log::v2s_mt_posix::trivial::severity_level>, void, void, void, void, void, void, void, void, void> >::open_record<boost::parameter::aux::tagged_argument<boost::log::v2s_mt_posix::keywords::tag::severity, boost::log::v2s_mt_posix::trivial::severity_level const> >(boost::parameter::aux::tagged_argument<boost::log::v2s_mt_posix::keywords::tag::severity, boost::log::v2s_mt_posix::trivial::severity_level const> const&) in trivial_log_test-6968b8.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Several similar questions said that the following gave useful information:
$ clang++ -E -x c++ - -v < /dev/null
Apple LLVM version 7.0.2 (clang-700.1.81)
Target: x86_64-apple-darwin15.3.0
Thread model: posix
"/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang" -cc1 -triple x86_64-apple-macosx10.11.0 -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -E -disable-free -disable-llvm-verifier -main-file-name - -mrelocation-model pic -pic-level 2 -mthread-model posix -mdisable-fp-elim -masm-verbose -munwind-tables -target-cpu core2 -target-linker-version 253.9 -v -dwarf-column-info -resource-dir /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/7.0.2 -stdlib=libc++ -fdeprecated-macro -fdebug-compilation-dir /Users/chap/private/cpp/BOOST_TESTING/log_test -ferror-limit 19 -fmessage-length 176 -stack-protector 1 -mstackrealign -fblocks -fobjc-runtime=macosx-10.11.0 -fencode-extended-block-signature -fcxx-exceptions -fexceptions -fmax-type-align=16 -fdiagnostics-show-option -fcolor-diagnostics -o - -x c++ -
clang -cc1 version 7.0.2 based upon LLVM 3.7.0svn default target x86_64-apple-darwin15.3.0
ignoring nonexistent directory "/usr/include/c++/v1"
#include "..." search starts here:
#include <...> search starts here:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1
/usr/local/include
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/7.0.2/include
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include
/usr/include
/System/Library/Frameworks (framework directory)
/Library/Frameworks (framework directory)
End of search list.
# 1 "<stdin>"
# 1 "<built-in>" 1
# 1 "<built-in>" 3
# 332 "<built-in>" 3
# 1 "<command line>" 1
# 1 "<built-in>" 2
# 1 "<stdin>" 2
Homebrew is installed and up-to-date. I reinstalled Boost:
$ brew reinstall boost
==> Reinstalling boost
==> Downloading https://homebrew.bintray.com/bottles/boost-1.60.0_1.el_capitan.bottle.tar.gz
Already downloaded: /Library/Caches/Homebrew/boost-1.60.0_1.el_capitan.bottle.tar.gz
==> Pouring boost-1.60.0_1.el_capitan.bottle.tar.gz
🍺 /usr/local/Cellar/boost/1.60.0_1: 11,139 files, 436.0M
In other similar questions about link errors using the Boost libraries, a common solution was to run bootstrap.sh to build the b2 executable to compile some libraries. However, these people installed Boost without using Homebrew. Homebrew's installation of Boost looks different than the directory structure that's described by the Boost 'getting started' page - notably in that it doesn't contain either the bootstrap.sh script or the b2 binary. This makes me think that brew install boost has taken care of it.
Can someone suggest a next step?
UPDATE 1: Corrected statement about bootstrap.sh and b2.
回答1:
The solution, provided by someone on the Homebrew mailing list, was to compile my program using the following flags:
c++ -DBOOST_LOG_DYN_LINK -lboost_log-mt trivial_log_test.cpp
Since I got the Boost "bottle", I got prebuilt versions of the binary libraries. No need for bootstrap.sh / b2.
来源：https://stackoverflow.com/questions/36117306/link-errors-using-homebrews-boostlog-in-osx-el-capitan