轉載：http://blog.csdn.net/wudiwo/article/details/7682320
Eclipse 中新建C 或C ++到項目時，頭文件報警，顯示“Unresolved inclusion:<stdio.h>” 雖然不影響項目到編譯和運行，確也無法查看頭文件，讓人感覺實在不爽。下面是在國外到網站上看到解決方案，自己整理了一下拿來分享一下。關於在Eclipse 下配置C /C ++ 開發環境這里不多說了。
在終端下查看C 庫文件到路徑：
$ echo "int main() { return 0; }" > a1.c
$ gcc -v a1.c
#include "..." search starts here:
#include <...> search starts here:
/usr/lib/gcc/x86_64-linux-gnu/4.9/include
/usr/local/include
/usr/lib/gcc/x86_64-linux-gnu/4.9/include-fixed
/usr/include/x86_64-linux-gnu
/usr/include
搜索列表結束。
……
查看C++ 庫文件到搜索路徑：
$ echo "int main() { return 0; }" > a1.cpp
$ g++ -v a1.cpp
#include "..." search starts here:
#include <...> search starts here:
/usr/include/c++/4.9
/usr/include/x86_64-linux-gnu/c++/4.9
/usr/include/c++/4.9/backward
/usr/lib/gcc/x86_64-linux-gnu/4.9/include
/usr/local/include
/usr/lib/gcc/x86_64-linux-gnu/4.9/include-fixed
/usr/include/x86_64-linux-gnu
/usr/include
搜索列表結束。
上述路徑因人而異。
在eclipse中菜單Window --> Preferences --> C/C++ --> Build --> Environment添加環境變量
C_INCLUDE_PATH =/usr/lib/gcc/x86_64-linux-gnu/4.9/include:/usr/local/include:/usr/lib/gcc/x86_64-linux-gnu/4.9/include-fixed:/usr/include/x86_64-linux-gnu:/usr/include
CPLUS_INCLUDE_PATH =/usr/include/c++/4.9:/usr/include/x86_64-linux-gnu/c++/4.9:/usr/include/c++/4.9/backward:/usr/lib/gcc/x86_64-linux-gnu/4.9/include:/usr/local/include:/usr/lib/gcc/x86_64-linux-gnu/4.9/include-fixed:/usr/include/x86_64-linux-gnu:/usr/include
記得選中下面的Append variables to native environment.
添加完后重啟Eclipse 新建項目即可。