Eclipse 中新建C 或C ++到项目时，头文件报警，显示“Unresolved inclusion:<stdio.h>” 虽然不影响项目到编译和运行，确也无法查看头文件，让人感觉实在不爽。下面是在国外到网站上看到解决方案，自己整理了一下拿来分享一下。关于在Eclipse 下配置C /C ++ 开发环境这里不多说了。
在终端下查看C 库文件到路径：
$ echo "int main() { return 0; }" > a1.c
$ gcc -v a1.c
#include "..." 搜索从这里开始：
#include <...> 搜索从这里开始：
/usr/lib/gcc/i686-linux-gnu/4.6.1/include
/usr/local/include
/usr/lib/gcc/i686-linux-gnu/4.6.1/include-fixed
/usr/include/i386-linux-gnu
/usr/include
搜索列表结束。
……
查看C++ 库文件到搜索路径：
$ echo "int main() { return 0; }" > a1.cpp
$ g++ -v a1.cpp
#include "..." 搜索从这里开始：
#include <...> 搜索从这里开始：
/usr/include/c++/4.6
/usr/include/c++/4.6/i686-linux-gnu/.
/usr/include/c++/4.6/backward
/usr/lib/gcc/i686-linux-gnu/4.6.1/include
/usr/local/include
/usr/lib/gcc/i686-linux-gnu/4.6.1/include-fixed
/usr/include/i386-linux-gnu
/usr/include
搜索列表结束。
在eclipse中菜单Window --> Preferences --> C/C++ --> Build --> Environment添加环境变量
C_INCLUDE_PATH =/usr/lib/gcc/i686-linux-gnu/4.6.1/include:/usr/local/include:/usr/lib/gcc/i686-linux-gnu/4.6.1/include-fixed:/usr/include/i386-linux-gnu:/usr/include
CPLUS_INCLUDE_PATH =/usr/include/c++/4.6:/usr/include/c++/4.6/i686-linux-gnu/.:/usr/include/c++/4.6/backward:/usr/lib/gcc/i686-linux-gnu/4.6.1/include:/usr/local/include:/usr/lib/gcc/i686-linux-gnu/4.6.1/include-fixed:/usr/include/i386-linux-gnu:/usr/include
记得选中下面的Append variables to native environment.
添加完后重启Eclipse 新建项目即可。
eclipse上配置好cdt后，新建一个简单的项目测试下，当写入头文件时，却出现如下错误提示：
unresolved inclusion: <stdio.h>
原因与解决：
这是c/c++标准库未设置所致。解决方法如下。
选中项目，依次操作：
右键单击 -> properties -> C/C++ General -> Paths and Symbols -> Add... -> file system.
然后选择c/c++库的位置：/usr/include
如此再继续添加/usr/include/c++路径。确定后即可
参考：
Eclipse reports Unresolved inclusion for system headers such as stdio.h if it cannot locate the header files for a project. You can resolve this by right-clicking on the project in the Project Explorer view and then selecting Properties... from the context menu. In the dialog box, select: C/C++ General → Paths and Symbols → Add... and then add the path to the ARM Compiler headers on your host workstation. For example, C:\Program Files\DS-5\include. Select both Add to all configurations and Add to all languages, click on Apply so that Eclipse can rebuild the index.