Without this change build will fail when using gold linker

[sochotnicky]

This is needed for certain optimization levels with llvm

[rakshasa]

Could you be more specific, what optimization levels and why does it require it? (I can guess why, but rather have it explicitly stated)

[sochotnicky]

This optimization is called LTO, implemented currently in GCC[1] as well as LLVM[2]. LLVM starts to use LTO when -O4 is used (equivalent to "-O3 -oflto").

Some more information can be found on LLVM web[3]

[1] http://gcc.gnu.org/wiki/LinkTimeOptimization
[2] http://llvm.org/docs/LinkTimeOptimization.html
[3] http://llvm.org/docs/GoldPlugin.html

[rakshasa]

Ok, I'll test it out once in a couple of days.

[jlec]

The original patch was initiated by me.
I am using the ld.gold linker instead of the ld.bfd. As gold as a stronger detection of underlinking problems, it needs this patch. Otherwise you get this error:

libtool: link: x86_64-pc-linux-gnu-g++ -O2 -pipe -ftracer -march=corei7-avx -mtune=corei7-avx -mcx16 -msahf -mno-movbe -maes -mpclmul -mpopcnt -mno-abm -mno-lwp -mno-fma -mno-fma4 -mno-xop -mno-bmi -mno-tbm -mavx -msse4.2 -msse4.1 --param l1-cache-size=32 --param l1-cache-line-size=64 --param l2-cache-size=8192 -frecord-gcc-switches -g -Wenum-compare -DNDEBUG -I/usr/include/sigc++-2.0 -I/usr/lib64/sigc++-2.0/include -Wl,-O1 -Wl,--as-needed -Wl,-O1 -Wl,--hash-style=gnu -Wl,--sort-common -o rtorrent main.o libsub_root.a ui/libsub_ui.a core/libsub_core.a display/libsub_display.a input/libsub_input.a rpc/libsub_rpc.a utils/libsub_utils.a -lncursesw -lcurl /usr/lib64/libtorrent.so -lcrypto -lsigc-2.0
thread_base.cc:131: error: undefined reference to 'pthread_create'
thread_base.cc:208: error: undefined reference to 'pthread_kill'
thread_base.cc:200: error: undefined reference to 'pthread_kill'
collect2: ld returned 1 exit status