Eric Blake wrote: > According to Jim Meyering on 3/19/2009 3:58 PM: >> * src/dd.c (O_FULLBLOCK): Compute its value via cpp macros that >> expand to less than 3KB of rather than to 180KB(!). > > Why use a macro at all? All we have to do is come up with a value that is > bitwise distinct from all the others. In other words, much smaller than > 3KB, let alone 180KB. > > -- > Don't work too hard, make some time for fun as well! > > Eric Blake e...@byu.net >>From d6a83c9d49c2737a9a0ef9ca7fc4bb9f469e9576 Mon Sep 17 00:00:00 2001 > From: Eric Blake <e...@byu.net> > Date: Thu, 19 Mar 2009 22:31:16 -0600 > Subject: [PATCH] dd: use a more portable definition of O_FULLBLOCK > > * src/dd.c (O_FULLBLOCK): Compute its value without using a 180KB > macro. This avoids triggering a compilation failure with HP-UX's cc. > Reported by Matthew Woehlke.
I like it. Thanks. However, I'd like to keep O_FULLBLOCK as a single-bit value. That's slightly less surprising, and makes the change a tad smaller. How about this? >From 8e48bb674042700f7c091f053ae5128e6ca691d7 Mon Sep 17 00:00:00 2001 From: Eric Blake <e...@byu.net> Date: Thu, 19 Mar 2009 20:14:26 +0100 Subject: [PATCH] dd: use a more portable definition of O_FULLBLOCK * src/dd.c (O_FULLBLOCK): Compute its value without using a 180KB macro. This avoids triggering a compilation failure with HP-UX's cc. Reported by Matthew Woehlke. --- src/dd.c | 33 ++++++++++++++++++--------------- 1 files changed, 18 insertions(+), 15 deletions(-) diff --git a/src/dd.c b/src/dd.c index 9a1c875..a1bbd7f 100644 --- a/src/dd.c +++ b/src/dd.c @@ -265,23 +265,26 @@ static struct symbol_value const conversions[] = enum { - /* Use a value that is larger than that of any other O_ symbol. */ - O_FULLBLOCK = ((MAX (O_APPEND, - MAX (O_BINARY, - MAX (O_CIO, - MAX (O_DIRECT, - MAX (O_DIRECTORY, - MAX (O_DSYNC, - MAX (O_NOATIME, - MAX (O_NOCTTY, - MAX (O_NOFOLLOW, - MAX (O_NOLINKS, - MAX (O_NONBLOCK, - MAX (O_SYNC, - MAX (O_TEXT, 0)))))))))))))) << 1) + /* Compute a value that's bitwise disjoint from the union + of all O_ values. */ + v = ~(O_APPEND + | O_BINARY + | O_CIO + | O_DIRECT + | O_DIRECTORY + | O_DSYNC + | O_NOATIME + | O_NOCTTY + | O_NOFOLLOW + | O_NOLINKS + | O_NONBLOCK + | O_SYNC + | O_TEXT), + /* Use its lowest bit. */ + O_FULLBLOCK = v ^ (v & (v - 1)) }; -/* Ensure that we didn't shift it off the end. */ +/* Ensure that we got something. */ verify (O_FULLBLOCK != 0); #define MULTIPLE_BITS_SET(i) (((i) & ((i) - 1)) != 0) -- 1.6.2.rc1.285.gc5f54 _______________________________________________ Bug-coreutils mailing list Bug-coreutils@gnu.org http://lists.gnu.org/mailman/listinfo/bug-coreutils