Thank you for the explanation but you did not explain the role of "include_next" here!! You only insisted on some path is ignored!!! I know that when we use -I and there is the same pathname in the system , -I is ignored!! But WHERE "include_next" is used? Is it used with -isystem and in the file it is introducing ONLY? Please rewrite this part of gcc manual, it is not clear at all!! On Sun, May 1, 2011 at 3:17 AM, Ian Lance Taylor <iant@xxxxxxxxxx> wrote: > Jonathan Wakely <jwakely.gcc@xxxxxxxxx> writes: > >> On 30 April 2011 12:39, ali hagigat wrote: >>> 3.14 Options for Directory Search >>> -Idir >>> This is to ensure that GCC’s procedure to fix buggy system >>> headers and the ordering for the include next directive are not >>> inadvertently hanged. >>> ----------------------------- >>> Sorry I do not have the answer yet!! I understood "include_next" >>> directive but what is the procedure of GCC to fix the system headers? >> >> GCC installs fixed versions of buggy system headers, as part of the >> gcc installation tree. Those headers are used instead of the original >> system ones. >> >> >>> When we specify a path with -I and it is ignored because there is the >>> same name in the system directories, how it can fix the system headers >>> then? >> >> Because the system directories (including the one containing the fixed >> headers) are still searched as normal. >> >> It really isn't complicated: if a directory is considered as a system >> directory and it is also named with -I, then the -I option is ignored. >> BUT THE DIRECTORY IS STILL SEARCHED AS A SYSTEM DIRECTORY. >> >> Like Ian said, if you say: >> -isystem foo -I foo >> then the -I option is ignored and it is equivalent to: >> -isystem foo >> >> This ensures that if 'foo' contains buggy system headers then those >> headers will not be found before the fixed versions, because gcc >> searches the directory containing the fixed headers before it searches >> other system directories. > > > It is straightforward to test these options with a working version of > gcc, to help clarify the documentation in your own mind. > > Ian >
