RE: Help - header include issues

[Sudeep George <sudeep.george@xxxxxxxxxxx>]

-----Original Message-----
From: kernelnewbies-bounce@xxxxxxxxxxxx
[mailto:kernelnewbies-bounce@xxxxxxxxxxxx] On Behalf Of Davidlohr Bueso
A
Sent: Tuesday, May 25, 2004 1:32 PM
To: c.lucas@xxxxxxxxxxx; whereisit28@xxxxxxxxx
Cc: kernelnewbies@xxxxxxxxxxxx
Subject: Re: Help - header include issues

On Sat, 2004-05-22 at 03:41, Christophe Lucas wrote:
> l x (whereisit28@xxxxxxxxx) wrote:
> > Hi,
> > 
> > I found a very stange problem related to header file
> > includ.  Could some one take a look and see what
> > causes the problem?
> > 
> > One C source file needs to include 2 system header
> > files scsi.h and hosts.h.  They both are under
> > /usr/src/linux-2.4.18-14/drivers/scsi/ and hosts.h
> > uses structures defined in scsi.h.
> > 
> > To avoid using hard-coded path when including them in
> > the c file, the following two lines are added to the
> > Makefile:
> > 
> > INCLUDE_PATH = -I$//usr/src/linux-`uname
> > -r`/drivers/scsi
> > [...] 
> > Everything is compiled okay.  This means the path
> > included in the Makefile works okay because it can
> > find hosts.h.
> > 
> > (2) If I include them like this:
> > 
> > #include <scsi.h>
> > #include <hosts.h>
> > 
> > Compile errors show structures used by hosts.h can not
> > be found, meaning scsi.h can not be found.
> > 
> > This is strange.  Why only one header file can be
> > found but not the other while both of them are in the
> > same directory?  What can be wrong? 
> 
> I think you must include them by :
> #include "scsi.h"
> #include "hosts.h"
> 
> Perhaps I make a mistake, If it is true, please correct me :-)
> 

> #include "my_header.h" == #include <my_header.h>
> The " " and < > are just coding conventions.

There is a difference between using #include <> and #include ""
Pasting the relevant section from the "The C Preprocessor" manual:
------------------------------------------------------------------------
----
"GCC looks in several different places for headers. On a normal Unix
system, if you do not instruct it otherwise, it will look for headers
requested with #include <file> in:
/usr/local/include
/usr/lib/gcc-lib/target/version/include
/usr/target/include
/usr/include

You can add to this list with the '-Idir' command line option. All the
directories named by '-I' are searched, in left-to-right order, before
the default directories. 
GCC looks for headers requested with #include "file" first in the
directory containing the current file, then in the same places it would
have looked for a header requested with angle brackets."
------------------------------------------------------------------------
--

Hope this helps w.r.t to the problem in picking up the <scsi.h> file

> Have a good day :)
You too 

Dave

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