dyld: Symbol not found: _ERR_remove_thread_state - libtorrent

Question

I’m trying to run the make_torrent example code provide over here.
I’m have compiled and installed libtorrent based on what written over here
Here how I have complied and linked the make_torrent.cc file.
g++ -g -Wall make_torrent.cc -ltorrent-rasterbar -lboost_system -o make_torrent
Upon running the make_torrent sample code I see this
usage: make_torrent FILE [OPTIONS]
Generates a torrent file from the specified file
or directory and writes it to standard out
OPTIONS:
-m file generate a merkle hash tree torrent.
merkle torrents require client support
the resulting full merkle tree is written to
the specified file
-w url adds a web seed to the torrent with
the specified url
-t url adds the specified tracker to the
torrent. For multiple trackers, specify more
-t options
-c comment sets the comment to the specified string
-C creator sets the created-by field to the specified string
-p bytes enables padding files. Files larger
than bytes will be piece-aligned
-s bytes specifies a piece size for the torrent
This has to be a multiple of 16 kiB
-l Don't follow symlinks, instead encode them as
links in the torrent file
-o file specifies the output filename of the torrent file
If this is not specified, the torrent file is
printed to the standard out, except on windows
where the filename defaults to a.torrent
-r file add root certificate to the torrent, to verify
the HTTPS tracker
-S info-hash add a similar torrent by info-hash. The similar
torrent is expected to share some files with this one
-L collection add a collection name to this torrent. Other torrents
in the same collection is expected to share files
with this one.
-M make the torrent compatible with mutable torrents
this means aligning large files and pad them in order
for piece hashes to uniquely indentify a file without
overlap
dyld: lazy symbol binding failed: Symbol not found: _ERR_remove_thread_state
Referenced from: /usr/local/lib/libtorrent-rasterbar.9.dylib
Expected in: flat namespace
dyld: Symbol not found: _ERR_remove_thread_state
Referenced from: /usr/local/lib/libtorrent-rasterbar.9.dylib
Expected in: flat namespace
I know I have to provide the relevant argument to make torrent but I’m not sure why libtorrent is complaining about the linker
g++ --version
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 8.0.0 (clang-800.0.42.1)
Target: x86_64-apple-darwin16.4.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin
Any clue?

Answer 1

This is caused by not linking to openssl correctly. I'm assuming you're on OSX, which has an old version of openssl in the default install path.
I would suggest installing openssl with brew install openssl. Note that this requires you have homebrew installed.
After doing this, do brew info openssl and look lines telling you what to add to your LDFLAGS and CPPFLAGS. In my case:
For compilers to find this software you may need to set:
LDFLAGS: -L/usr/local/opt/openssl/lib
CPPFLAGS: -I/usr/local/opt/openssl/include
For pkg-config to find this software you may need to set:
PKG_CONFIG_PATH: /usr/local/opt/openssl/lib/pkgconfig
So in my case, I would then compile with:
g++ -g -Wall -L/usr/local/opt/openssl/lib -I/usr/local/opt/openssl/include make_torrent.cc -ltorrent-rasterbar -lboost_system -o make_torrent
If this does not work, I would also make sure that you include these flags when compiling libtorrent.