Re: typedefs and structs [was Re: [PATCH 16/42]: PCI: PCI Error reporting callbacks]

[linas <linas@austin.ibm.com>]

On Mon, Nov 07, 2005 at 11:02:45AM -0800, Greg KH was heard to remark:
> 
> > I'm not to clear on what "sparse" can do; however, in the good old days,
> > gcc allowed you to commit great sins when passing "struct blah *" to 
> > subroutines, whereas it stoped you cold if you tried the same trick 
> > with a typedef'ed "blah_t *".  This got me into the habit of turning
> > all structs into typedefs in my personal projects.  Can we expect
> > something similar for the kernel, and in particular, should we start
> > typedefing structs now?
> 
> No, never typedef a struct.  That's just wrong.  

Its a defacto convention for most C-language apps, see, for 
example Xlib, gtk and gnome.  Also, "grep typedef include/linux/*"
shows that many kernel device drivers use this convention.

> gcc should warn you
> just the same if you pass the wrong struct pointer 

There were many cases where it did not warn (I don't remember 
the case of subr calls). I beleive this had to do with ANSI-C spec
issues dating to the 1990's; traditional C is weakly typed.

Its not just gcc; anyoe who coded for a while eventually discovered
that tyedefs where strongly typed, but "struct blah *" were not.

> (and all of your code
> builds without warnings, right?)

:-/  Yes, of course.

--linas
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