-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi, You haven't written what kind of environment you are using, so I in the later I will assume it is linux or BSD. See my comments below. loody írta: > Dear all: > in gcc document there is an option as > -nostdinc > Do not search the standard system directories for header > files. Only the directories you have specified with -I > options (and the directory of the current file, if appropriate) > are searched > Is that used to tell where the headers that gcc can get the size of > some already define data types? Unless you are a kernel developer you shouldn't use -nostdinc, because gcc will not found essential header files. By default as you have written, gcc is looking for header files in the following locations (maybe in different order): o standard system directories: - this is the directory where standard headers installed, and this location is the same for the whole system and cannot be changed. - this directory is usually /usr/include and /usr/local/include on a Unix like system. - you can change the location of standard system directory with $C_INCLUDE_PATH and $CPLUS_INCLUDE_PATH env. variables. - if this directory is empty it means that you don't have installed your development environment properly eg. libc/glibc is not installed which is the standard C library. o In directory where your source code is. These headers are part of your program. o In directories you specified with -I.. command line options. These headers are usually not part of your program (or not in the same directory) neither a system wide library. E.g.: a library you have downloaded but have not installed system wide, or if you want to use a library which has different version than the one installed on your system. So if you use -nostdinc, gcc simply ignores the standard headers. This is only useful if you are writing a program which doesn't use standard library at all, or you want to use a different standard library and in this case you must tell its location to gcc with -I/path/to/your/headers. > If my assumption is correct, is there any command or options I can use > to check where is the path that my gcc search for, since I always get > error messages as "cannot find stddef.h" ? > I have type "gcc -v" but i have no idea which one can tell me where > the stdinc path it looks for? > appreciate your help, > miloody I dont know how to get them in an exact way, but I'm pretty sure gcc will look in the directories I wrote above. But be careful, if you use - -nostdinc, it will skip system headers! stddef.h is not part of glibc, but part of gcc itself, and on my system it is located in a compiler specific directory. I used gcc -v and looked for --includedir=... to get its path, but it didn't tell me the location of standard header files. Maybe it is "include" added to the path specified with --prefix=... ? I'm not sure. Have a nice day, Tibor -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAksJiYUACgkQRH5UCDZswS0YOACfYaQcnsdeFQtjGrStkPAm7GFO G0AAoMNC/k+rnWzFCrMxKst4kUUrayU0 =1Lbz -----END PGP SIGNATURE-----
