Messages in this thread | | | From | Gabriel Paubert <> | Date | Wed, 12 May 2004 21:34:38 +0200 | Subject | Re: GCC nested functions? |
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On Wed, May 12, 2004 at 10:59:24AM -0700, Stephen Hemminger wrote: > I used GCC nested functions in the (not released) bridge sysfs interface for 2.6.6. > It seemed like a nice way to express the sysfs related interface without doing > lots of code copying (or worse lots of macros). > > The code in question looks like: > static ssize_t store_bridge_parm(struct class_device *cd, > const char *buf, size_t len, > void (*store)(struct net_bridge *, unsigned long)) > { > struct net_bridge *br = to_bridge(cd); > char *endp; > unsigned long val; > > if (!capable(CAP_NET_ADMIN)) > return -EPERM; > > val = simple_strtoul(buf, &endp, 0); > if (endp == buf) > return -EINVAL; > > spin_lock_bh(&br->lock); > store(br, val); > spin_unlock_bh(&br->lock); > return len; > } > ... > > static ssize_t store_forward_delay(struct class_device *cd, const char *buf, > size_t len) > { > void store(struct net_bridge *br, unsigned long val) > { > unsigned long delay = clock_t_to_jiffies(val); > br->forward_delay = delay; > if (br_is_root_bridge(br)) > br->bridge_forward_delay = delay; > } > > return store_bridge_parm(cd, buf, len, store); > } > > > This works fine for GCC 2.95 and 3.X for i386 and x86_64 architectures, but the ia64 > (cross compiler) pukes with: > > In function `store_forward_delay': > : undefined reference to `__ia64_trampoline' > > Redoing it as separate functions is easy enough, but the questions are: > - Are gcc nested functions allowed in the kernel? If not where should > this restriction be put in Documentation? CodingStyles?
There is some kind of implicit prohibition in Documentation/CodingStyle (Chapter3: Placing braces):
"Heretic people all over the world have claimed that this inconsistency is ... well ... inconsistent, but all right-thinking people know that (a) K&R are _right_ and (b) K&R are right. Besides, functions are special anyway (you can't nest them in C)." ^^^^^^^^^^^^^^^^^^^^^^^^^^^
Maybe the way it is stated is too close so subliminal ;-) But I never found a real need for them in C.
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