thanks robert for clearing up my fundamentals . warm regards sandeep dey ----- Original Message ----- From: "Robert Love" <rml@tech9.net> To: "sandeep dey" <sandey@iitk.ac.in> Cc: "paridhi bansal" <paridhibansal@yahoo.com>; <kernelnewbies@nl.linux.org> Sent: Saturday, November 23, 2002 1:39 PM Subject: Re: global variables > On Sun, 2002-11-24 at 05:50, sandeep dey wrote: > > > just declare the global variables as extern in other files > > and use them.i.e declare them as 'extern int k;' > > (int k or anything you would like to declare) > > take care of double global varibles with same name > > and don't initialise an extern variable where it was declared.i.e (don't > > use 'extern int k=0;') > > This is a recipe for disaster in a large project (i.e. the kernel). > > The best solution is to use externs, but do not just "declare the global > variables as extern in other files" as you will have no type checking. > > Instead, in a header file associated with whatever you are doing, > declare the variable extern. Use that in your other files where you > need to use the global. Then (and this is the important part) also > include that same header where the variable is actually defined. Then > you will get your type checking, since the extern declaration must match > the actual definition. > > Look anywhere in the kernel for examples of this. > > Note, perhaps even better, do not have the variables accessible > externally at all. If needed, export functions to access them (i.e. > get_foo() and set_foo()). The scheduler is a good example of where we > did this. > > Whenever I see an extern plopped right above where it is used, I am > always suspicious. > > Robert Love > -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
