Messages in this thread |  | | | From | Linus Torvalds <> | | Date | Tue, 24 Jul 2012 12:09:41 -0700 | | Subject | Re: [PATCH v2] posix_types.h: make __NFDBITS compatible with glibc definition |
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On Tue, Jul 24, 2012 at 12:03 PM, Josh Boyer <jwboyer@redhat.com> wrote: > > FWIW, the definitions of __FD_ELT/__FD_MASK in glibc are: > > #define __FD_ELT(d) ((d) / __NFDBITS) > #define __FD_MASK(d) ((__fd_mask) 1 << ((d) % __NFDBITS)) > > where __fd_mask is 'typdef long int'.
Yeah, that's not good.
If __NFDBITS is signed (and it is), and "d" is a signed type, that division and modulus now create stupid extra code with conditionals (assuming 'd' isn't constant, of course).
So changing the sign of __NFDBITS has these kinds of subtle side effects that clearly the glibc people didn't actually think about.
What was the *advantage* of that stupidity?
Quite frankly, if you want to make NFDBITS be an "int", then it should have been done at that
#define NFDBITS ((int)__NFDBITS)
level, not at "__NFDBITS". Exactly because the unsigned type there matters.
Does anybody in the glibc camp care about efficient and small code AT ALL?
Linus
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