clang++を使う

c++入門しようと思ったらいきなり詰まりました. clang++を使ってコンパイルしようとしたら,

cp0001.cpp:1:10: fatal error: 'iostream' file not found
#include <iostream>
          ^
1 error generated.

iostreamがない…?

% g++ cp0001.cpp 
% ./a.out

Hello

あるっぽい.

iostreamはちゃんとあるらしい.
やっぱパスの問題らしい.
どこにあるか探してみる.

% find /usr/include -name iostream 
/usr/include/c++/4.2.1/iostream

あるっぽい.

インクルードパスを追加して,もう一度コンパイル

% clang++ -v cp0001.cpp -I /usr/include/c++/4.2.1

オプションについて
-I Add directory to include search path
-v Show commands to run and use verbose output

-v オプションで,コンパイル時のclang++コマンドの詳細が表示できるらしい.

参考:http://kaworu.jpn.org/cpp/clang++


% clang++ -v cp0001.cpp -I /usr/include/c++/4.2.1
clang version 3.4.1 (tags/RELEASE_34/dot1-final)
Target: x86_64-apple-darwin13.3.0
Thread model: posix
 "/usr/local/llvm/bin/clang" -cc1 -triple x86_64-apple-macosx10.9.0 -emit-obj -mrelax-all -disable-free -main-file-name cp0001.cpp -mrelocation-model pic -pic-level 2 -mdisable-fp-elim -masm-verbose -munwind-tables -target-cpu core2 -target-linker-version 236.4 -v -resource-dir /usr/local/llvm/bin/../lib/clang/3.4.1 -I /usr/include/c++/4.2.1 -I /usr/local/include -stdlib=libc++ -fdeprecated-macro -fdebug-compilation-dir /Users/mao/exercises/c++ -ferror-limit 19 -fmessage-length 99 -stack-protector 1 -mstackrealign -fblocks -fobjc-runtime=macosx-10.9.0 -fencode-extended-block-signature -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -vectorize-slp -o /var/folders/n0/kt8bmlgs0h39kg8p8zc1g__00000gn/T/cp0001-17d3be.o -x c++ cp0001.cpp
clang -cc1 version 3.4.1 based upon LLVM 3.4.1 default target x86_64-apple-darwin13.3.0
ignoring nonexistent directory "/usr/local/llvm/bin/../include/c++/v1"
ignoring nonexistent directory "/usr/include/c++/v1"
ignoring duplicate directory "/usr/local/include"
  as it is a non-system directory that duplicates a system directory
#include "..." search starts here:
#include <...> search starts here:
 /usr/include/c++/4.2.1
 /usr/local/include
 /usr/local/llvm/bin/../lib/clang/3.4.1/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 10.9.0 -o a.out /var/folders/n0/kt8bmlgs0h39kg8p8zc1g__00000gn/T/cp0001-17d3be.o -lc++ -lSystem /usr/local/llvm/bin/../lib/clang/3.4.1/lib/darwin/libclang_rt.osx.a
Undefined symbols for architecture x86_64:
  "std::ios_base::Init::Init()", referenced from:
      ___cxx_global_var_init in cp0001-17d3be.o
  "std::ios_base::Init::~Init()", referenced from:
      ___cxx_global_var_init in cp0001-17d3be.o
  "std::cout", referenced from:
      _main in cp0001-17d3be.o
  "std::basic_ostream<char, std::char_traits<char> >& std::operator<<<std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)", referenced from:
      _main in cp0001-17d3be.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

やっぱりうまくいかない.
よくわからない…

ここで完全に行き詰まってたわけですが,近くにいらっしゃったすごい人にお尋ねしたところ,clang++が怪しいってことで

% which clang++
/usr/local/llvm/bin/clang++

これは後から手動で入れたllvmのやつで,こいつのパスがうまくいってないようだ.
でも,デフォルトのclang++を使えばできるのではってことで,

% /usr/bin/clang++ cp0001.cpp 

できた!!

ということで,後から入れたllvmをどうにかします.