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From: "nsz at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug libc/27824] New: preadv2 and pwritev2 offset argument passing
 on 64bit targets
Date: Tue, 04 May 2021 14:56:05 +0000
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X-Bugzilla-Version: 2.33
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D27824

            Bug ID: 27824
           Summary: preadv2 and pwritev2 offset argument passing on 64bit
                    targets
           Product: glibc
           Version: 2.33
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: nsz at gcc dot gnu.org
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

the linux preadv2 offset arg passing code is

/* Provide a macro to pass the off{64}_t argument on p{readv,writev}{64}.  =
*/
#define LO_HI_LONG(val) \
 (long) (val), \
 (long) (((uint64_t) (val)) >> 32)

on a 64bit target the first arg contains the entire 64bit offset
but i'd expect the second arg to be fixed 0.

linux does not seem to look at the second arg now on 64bit targets,
but it seems cleaner to pass 0 instead of top 32bit of val.

x86_64 seems to fixed this but other targets still have the >> 32
logic.

--=20
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