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Date: Wed, 25 Sep 2013 16:35:14 +0200 From: Andrzej Pietrasiewicz <andrzej.p@...sung.com> To: charlebm@...il.com Cc: balbi@...com, Behan Webster <behanw@...verseincode.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, USB list <linux-usb@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] Remove VLAIS usage from gadget code - alternate patch Hi Mark, Nice to hear from you again; on Saturday LOT's dreamliner was not grounded and I have safely returned home ;) Please see my comments inline. W dniu 24.09.2013 19:56, charlebm@...il.com pisze: > From: Mark Charlebois <charlebm@...il.com> > > > --- linux.orig/drivers/usb/gadget/f_fs.c > +++ linux/drivers/usb/gadget/f_fs.c > @@ -30,6 +30,21 @@ > > #define FUNCTIONFS_MAGIC 0xa647361 /* Chosen by a honest dice roll ;) */ > > +/* Variable Length Array Macros **********************************************/ > +#define vla_struct(structname) size_t structname##__##next = 0 > +#define vla_struct_size(structname) structname##__##next > + > +#define vla_item(structname, type, name, n) \ > + type * structname##_##name; \ > + size_t structname##_##name##__##offset = \ > + (structname##__##next + __alignof__(type) - 1) & \ > + ~(__alignof__(type) - 1); \ > + size_t structname##_##name##__##sz = n * sizeof(type); \ most likely this shoud read: + size_t structname##_##name##__##sz = (n) * sizeof(type); \ otherwise vla_item(....., lang_count + 1); will expand to: size_t d_stringtabs__sz = lang_count + \ 1 * sizeof(struct usb_gadget_strings *); > + structname##__##next = structname##_##name##__##offset + \ > + structname##_##name##__##sz; > + > +#define vla_ptr(ptr,structname,name) structname##_##name = \ > + (__typeof__(structname##_##name))&ptr[structname##_##name##__##offset] <snip> > unsigned i = 0; > + vla_struct(d); > + vla_item(d, struct usb_gadget_strings *, stringtabs, > + lang_count + 1); Can you somehow avoid mixing code and declarations? The last thing in the expansion of this vla_item(.......) is an assignment, and > + vla_item(d, struct usb_gadget_strings, stringtab, lang_count); the first thing in expansion of the next vla_item(.......) is a declaration. GCC most likely will complain (issue a warning). One solution I can think of here (a bit hackish) is to use a braced group as an expression: define vla_item() in such a way that first it declares e.g. d_stringtabs__offset, then d_stringtabs__sz, and then struct usb_gadget_strings **d_stringtabs = ({d__next = d_stringtabs__offset + d_stringtabs__sz; NULL;}); I am not a fan of this kind of style, but can't think of any better way now. And I don't know what Clang thinks of it :O Thanks, AP -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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