In which I recall how to build stuff
It all started when I wanted to "relearn" C++. I use it everyday, but it's been so long since I first came across it 15 years ago that I've accumulated tons of bad habits and thought patterns etc, so I wanted to get a "beginner's mind" feel of it again.
The initial detour
Ok, I thought, let's read the 4th edition of Bjarne's introduction to C++, and meanwhile also get to know Boost with some familiarity.
So I downloaded the Boost libraries (which took a while), and then tried to build this basic example (from the Boost FAQ)
#include <iostream>
#include <algorithm>
#include <iterator>
using boost::lambda::_1;
int main() {
typedef std::istream_iterator<int> in;
std::for_each(
in(std::cin), in(), std::cout << (_1 * 3) << " ");
}
using Clang
clang -std=c++11 -stdlib=libc++ -I/opt/boost/boost_1_54_0 example.cc -o example
Fork in the road
No luck
/tmp/example-oWquCX.o: In function `__cxx_global_var_init3':
example.cc:(.text+0x71): undefined reference to `std::ios_base::Init::Init()'
example.cc:(.text+0x79): undefined reference to `std::ios_base::Init::~Init()'
/tmp/example-oWquCX.o: In function `main':
example.cc:(.text+0xb3): undefined reference to `std::cin'
example.cc:(.text+0xf0): undefined reference to `std::cout'
/tmp/example-oWquCX.o: In function `std::istream_iterator<int, char, std::char_traits<char>, long>::_M_read()':
(and more that I'll skip over right now).
Later I realized that this was probably my fault in not linking it correctly, but I immediately, inexplicably, decided "Aha! let's build clang from source!"
This might also have been because I had gotten bored of sudo apt-get install foo and longed for the (decade ago) days of emerge foo.
Deep in the woods
Luckily, this turned out to be well-documented, more or less.
So I got up to the point where I got and built clang:
$ svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm
$ cd llvm/tools
$ svn co http://llvm.org/svn/llvm-project/cfe/trunk clang
$ mkdir build && cd build
$ ../llvm/configure --prefix=/usr/clang_3_3 \
--enable-optimized --enable-targets=host
$ make -j 8
And I procedded to then build libcxx
$ svn co http://llvm.org/svn/llvm-project/libcxx/trunk libcxx
$ mkdir build_libcxx && cd build_libcxx
$ CC=clang CXX=clang++ cmake -G "Unix Makefiles" \
-DLIBCXX_CXX_ABI=libsupc++ \
-DLIBCXX_LIBSUPCXX_INCLUDE_PATHS="/usr/include/c++/4.6/;\
/usr/include/c++/4.6/x86_64-linux-gnu/" \
-DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr $HOME/Clang/libcxx
$ make
Mt. Doom
At this point I got a compiler error. Very sad. Too bad, I thought, we need to go deeper. Time for building gcc/g++ and a new version of the C++ standard library. My Ubuntu version only had gcc upto 4.6, and I found a mailing list post which suggested this might be fixed in 4.7.
I could have at this point decided to add a PPA repository and got the new libraries and binaries that way, but luckily this was also well-documented (thank you, "Solarian Programmer", whoever you are!).
So I went ahead and downloaded gcc, and what turned out to be its prerequisites, gmp, mpfr and mpc.
These I built in the usual way (configure, make, make install), and then had to refer to them while setting up gcc:
$ export LD_LIBRARY_PATH=/usr/gcc_4_7/lib:$LD_LIBRARY_PATH
$ export LIBRARY_PATH=/usr/lib/x86_64-linux-gnu/
$ export C_INCLUDE_PATH=/usr/include/x86_64-linux-gnu
$ export CPLUS_INCLUDE_PATH=/usr/include/x86_64-linux-gnu
$ ../gcc-4.7.2/configure --build=x86_64-linux-gnu --prefix=/usr/gcc_4_7 \
--with-gmp=/usr/gcc_4_7 --with-mpfr=/usr/gcc_4_7 \
--with-mpc=/usr/gcc_4_7 --enable-checking=release \
--enable-languages=c,c++,fortran --disable-multilib \
--program-suffix=-4.7
Now I could proceed where I left off earlier, with the libcxx build, after setting a couple of path variables:
$ export PATH=/usr/gcc_4_7/bin:$PATH
$ export LD_LIBRARY_PATH=/usr/gcc_4_7/lib:/usr/gcc_4_7/lib64:$LD_LIBRARY_PATH
A ray of hope
But first, I wanted to see if the new g++ could do what I had initially tried to do with clang:
$ g++4.7 -std=c++11 -I/opt/boost/boost_1_54_0 example.cc -o example
$ echo 1 2 3 | ./example
3 6 9
Whew, now I was getting somewhere.
I went back and re-ran cmake, and then libcxx built successfully.
And then of course, I retried my original example:
$ /usr/clang_3_3/bin/clang++ -std=c++11 -I/opt/boost/boost_1_54_0 example.cc -o example
and that worked too ... Woohoo!!
Finally, since I always measure running time:
$ time /usr/clang_3_3/bin/clang++ -std=c++11 -I/opt/boost/boost_1_54_0 example.cc -o example
real 0m0.848s
user 0m0.780s
sys 0m0.056s
$ time g++4.7 -std=c++11 -I/opt/boost/boost_1_54_0 example.cc -o example
real 0m0.714s
user 0m0.648s
sys 0m0.044s
Now to do something more than this example program ...