一般情况下,我们不随便在VC的tools-〉option-〉drictroy目录下添加头文件目录,除非我们确定我们的多个工程或者我们的工作总要用到某个库或什么的,我们才将那个库的header目录添加到这里。
如果我们只想在某个工程中添加头文件目录(不影响其他工程)的话,应该在Project->Settings->C/C++一栏的Additional include directories:编辑框中添加绝对或相对目录就好了。
转个MSDN的解释
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This form instructs the preprocessor to look for include files in the same directory of the file that contains the #include statement, and then in the directories of any files that include (#include) that file. The preprocessor then searches along the path specified by the /I compiler option, then along paths specified by the INCLUDE environment variable.
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This form instructs the preprocessor to search for include files first along the path specified by the /I compiler option, then, when compiling from the command line, along the path specified by the INCLUDE environment variable.