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Subjectwhose job is it to include various header files?

more a philosophy question than anything but, while poking around
the percpu stuff today, i noticed in the header file linux/percpu.h
the opening snippet:

#include <linux/preempt.h>
#include <linux/slab.h> /* For kmalloc() */
#include <linux/smp.h>
#include <linux/string.h> /* For memset() */
#include <linux/cpumask.h>
...

hmmm, i thought to myself (because that's how i refer to myself), i
wonder why this header file is including headers for kmalloc() and
memset() when this header file makes no reference to those routines.
let's see what happens if i remove them and:

$ make distclean
$ make defconfig [x86]
$ make

... chug chug chug ...

CC arch/x86/kernel/nmi_32.o
arch/x86/kernel/nmi_32.c: In function ‘check_nmi_watchdog’:
arch/x86/kernel/nmi_32.c:81: error: implicit declaration of function ‘kmalloc’
arch/x86/kernel/nmi_32.c:81: error: ‘GFP_KERNEL’ undeclared (first use in this function)
arch/x86/kernel/nmi_32.c:81: error: (Each undeclared identifier is reported only once
arch/x86/kernel/nmi_32.c:81: error: for each function it appears in.)
arch/x86/kernel/nmi_32.c:81: warning: assignment makes pointer from integer without a cast
arch/x86/kernel/nmi_32.c:118: error: implicit declaration of function ‘kfree’
make[1]: *** [arch/x86/kernel/nmi_32.o] Error 1
make: *** [arch/x86/kernel] Error 2
$

ok, now i know. but that means, of course, that nmi_32.c is
invoking kmalloc() without ever having included the necessary header
file for it -- it's just inheriting that from linux/percpu.h.

doesn't that (sort of) violate the kernel coding style? if a file
somewhere needs the contents of some header file, isn't it that file's
responsibility to explicitly include it, and not quietly realize it's
getting it from elsewhere?

rday
--


========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry:
Have classroom, will lecture.

http://crashcourse.ca Waterloo, Ontario, CANADA
========================================================================
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