This option does not make sense! When we use -I option, it is not used for ‘#include <file >’. Is that right? (If true, -I is equal to -iquotedir) Or -I search path is used for ‘#include <file >’ but the file is tagged as a system file? My another concern is the explanation of -I option!!: "If a standard system include directory, or a directory specified with ‘-isystem’, is also specified with ‘-I’, the ‘-I’ option will be ignored." In this case -I option and the directory after that are not ignored!! -I is replaced with -isystem. When you have written "ignored", it suggests that -I does not be considered. Then the manual continues: "The directory will still be searched but as a system directory at its normal position in the system include chain" When a beginner reads your sentence he asks what is the system include chain? and what is the normal position? Is it the point where -I has been used on the command line? or it is pointing to the directory of the system which is used by gcc when searching headers.
