GCC 기본 include 경로(default include path on GCC/G++)

gcc 도움말에 의하면 아래의 경로에서 기본적으로 include 파일을 찾게 된다는데

2.3 Search Path GCC looks in several different places for headers. On a normal Unix system, if you do not instruct it otherwise, it will look for headers requested with #include <file> in: /usr/local/include libdir/gcc/target/version/include /usr/target/include /usr/include [링크 : http://gcc.gnu.org/onlinedocs/cpp/Search-Path.html]

음.. 저 긴 옵션을 다 줘야 하는 이유는 먼지 모르겠지만,
아무튼 확인해보면 /usr/local/include가 /usr/include 보다 우선적으로 검색하게 된다.
그런 이유로 opencv가 /usr/local/include에 설치되는 듯하다.

$ g++ -v -x c -E - Using built-in specs. Target: i486-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.4.3-4ubuntu5' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --program-suffix=-4.4 --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-plugin --enable-objc-gc --enable-targets=all --disable-werror --with-arch-32=i486 --with-tune=generic --enable-checking=release --build=i486-linux-gnu --host=i486-linux-gnu --target=i486-linux-gnu Thread model: posix gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5)  COLLECT_GCC_OPTIONS='-v' '-E' '-shared-libgcc' '-mtune=generic' '-march=i486'  /usr/lib/gcc/i486-linux-gnu/4.4.3/cc1 -E -quiet -v - -D_FORTIFY_SOURCE=2 -mtune=generic -march=i486 -fstack-protector ignoring nonexistent directory "/usr/local/include/i486-linux-gnu" ignoring nonexistent directory "/usr/lib/gcc/i486-linux-gnu/4.4.3/../../../../i486-linux-gnu/include" ignoring nonexistent directory "/usr/include/i486-linux-gnu" #include "..." search starts here: #include <...> search starts here:  /usr/local/include  /usr/lib/gcc/i486-linux-gnu/4.4.3/include  /usr/lib/gcc/i486-linux-gnu/4.4.3/include-fixed  /usr/include End of search list. [링크 : http://gcc.gnu.org/ml/gcc-help/2007-09/msg00216.html]