| Message ID | CAKo4hF+R0m+gGjk+P36tXN3ztiFr+vRsXXwe3bDPkM2zPY62+g@mail.gmail.com |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [uclibc-ng-devel] _FILE_OFFSET_BITS=64 and preadv/pwritev prototypes | expand |
Hi Sergey, what does the patch fixes? Compiler warnings? Runtime issues? ... best regards Waldemar > Am 10.06.2018 um 22:28 schrieb Sergey Korolev <s.korolev@ndmsystems.com>: > > As preadv and pwritev accept off_t type the prototypes should be declared as follows > > extern ssize_t preadv (int __fd, const struct iovec *__iovec, int __count, > off_t __offset) __wur; > > extern ssize_t pwritev (int __fd, const struct iovec *__iovec, int __count, > off_t __offset) __wur; > > to take into account _FILE_OFFSET_BITS=64 define. > > I am not sure but probably it is better to redeclare these prototypes > by analogy with sendfile using __REDIRECT_NTH. > <Fix-prototypes-for-preadv-pwritev.patch> > _______________________________________________ > devel mailing list > devel@uclibc-ng.org > https://mailman.uclibc-ng.org/cgi-bin/mailman/listinfo/devel
This patch fixes a size of 4th argument in a prototype
in case of _FILE_OFFSET_BITS=64 to match an implementation
on 32 bit architectures
#ifdef __NR_pwritev
ssize_t
pwritev (int fd, const struct iovec *vector, int count, off_t offset)
{
unsigned long pos_l, pos_h;
pos_h = (unsigned long)((long long)offset >> 32);
pos_l = (unsigned long)((long long)offset);
return INLINE_SYSCALL (pwritev, 5, fd, vector, count, pos_l, pos_h);
}
#endif
A simple test program compiled with gcc 7.3 and -Wconversion
#include <stdio.h>
#include <stdint.h>
#include <sys/uio.h>
int main()
{
const off_t ofs = INT64_MAX;
pwritev(0, NULL, 0, ofs);
return 0;
}
gives a warning
test.c:9:22: warning: conversion to '__off_t {aka long int}' from 'off_t
{aka const long long int}' may alter its value [-Wconversion]
pwritev(0, NULL, 0, ofs);
^~~
Without the patch the prototype tells a compiler to pass only 32 bits
to preadv/pwritev definitions that gives a corrupted offset value.
On Mon, Jun 11, 2018 at 6:14 AM, Waldemar Brodkorb <wbx@uclibc-ng.org>
wrote:
> Hi Sergey,
> what does the patch fixes?
> Compiler warnings? Runtime issues? ...
>
> best regards
> Waldemar
>
> > Am 10.06.2018 um 22:28 schrieb Sergey Korolev <s.korolev@ndmsystems.com
> >:
> >
> > As preadv and pwritev accept off_t type the prototypes should be
> declared as follows
> >
> > extern ssize_t preadv (int __fd, const struct iovec *__iovec, int
> __count,
> > off_t __offset) __wur;
> >
>
> > extern ssize_t pwritev (int __fd, const struct iovec *__iovec, int
> __count,
> > off_t __offset) __wur;
> >
> > to take into account _FILE_OFFSET_BITS=64 define.
> >
> > I am not sure but probably it is better to redeclare these prototypes
> > by analogy with sendfile using __REDIRECT_NTH.
> > <Fix-prototypes-for-preadv-pwritev.patch>
> > _______________________________________________
> > devel mailing list
> > devel@uclibc-ng.org
> > https://mailman.uclibc-ng.org/cgi-bin/mailman/listinfo/devel
>
>
<div dir="ltr">This patch fixes a size of 4th argument in a prototype<div>in case of <span style="font-size:12.8px;text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">_FILE_OFFSET_BITS=64 </span>to match an implementation</div><div>on 32 bit architectures<div><div><br></div><div><div>#ifdef __NR_pwritev</div><div>ssize_t</div><div>pwritev (int fd, const struct iovec *vector, int count, off_t offset)</div><div>{</div><div> unsigned long pos_l, pos_h;</div><div><br></div><div> pos_h = (unsigned long)((long long)offset >> 32);</div><div> pos_l = (unsigned long)((long long)offset);</div><div><br></div><div> return INLINE_SYSCALL (pwritev, 5, fd, vector, count, pos_l, pos_h);</div><div>}</div><div>#endif</div></div><div><br></div></div></div><div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">A simple test program compiled with gcc 7.3 and -Wconversion</div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial"><br></div><div style="text-decoration-style:initial;text-decoration-color:initial"><div><div>#include <stdio.h></div><div>#include <stdint.h></div><div>#include <sys/uio.h></div><div><br></div><div>int main()</div><div>{</div><div> const off_t ofs = INT64_MAX;</div><div><br></div><div> pwritev(0, NULL, 0, ofs);</div><div><br></div><div> return 0;</div><div>}</div></div><div><br></div></div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">gives a warning</div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial"><br></div><div style="text-decoration-style:initial;text-decoration-color:initial"><div>test.c:9:22: warning: conversion to '__off_t {aka long int}' from 'off_t {aka const long long int}' may alter its value [-Wconversion]</div><div> pwritev(0, NULL, 0, ofs);</div><div> ^~~</div></div></div><div><br></div><div>Without the patch the prototype tells a compiler to pass only 32 bits</div><div>to preadv/pwritev definitions that gives a corrupted offset value.</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Jun 11, 2018 at 6:14 AM, Waldemar Brodkorb <span dir="ltr"><<a href="mailto:wbx@uclibc-ng.org" target="_blank">wbx@uclibc-ng.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi Sergey,<br>
what does the patch fixes?<br>
Compiler warnings? Runtime issues? ...<br>
<br>
best regards<br>
Waldemar <br>
<div><div class="h5"><br>
> Am 10.06.2018 um 22:28 schrieb Sergey Korolev <<a href="mailto:s.korolev@ndmsystems.com">s.korolev@ndmsystems.com</a>>:<br>
> <br>
> As preadv and pwritev accept off_t type the prototypes should be declared as follows<br>
> <br>
> extern ssize_t preadv (int __fd, const struct iovec *__iovec, int __count,<br>
> off_t __offset) __wur;<br>
> <br>
> extern ssize_t pwritev (int __fd, const struct iovec *__iovec, int __count,<br>
> off_t __offset) __wur;<br>
> <br>
> to take into account _FILE_OFFSET_BITS=64 define.<br>
> <br>
> I am not sure but probably it is better to redeclare these prototypes<br>
> by analogy with sendfile using __REDIRECT_NTH.<br>
</div></div>> <Fix-prototypes-for-preadv-<wbr>pwritev.patch><br>
> ______________________________<wbr>_________________<br>
> devel mailing list<br>
> <a href="mailto:devel@uclibc-ng.org">devel@uclibc-ng.org</a><br>
> <a href="https://mailman.uclibc-ng.org/cgi-bin/mailman/listinfo/devel" rel="noreferrer" target="_blank">https://mailman.uclibc-ng.org/<wbr>cgi-bin/mailman/listinfo/devel</a><br>
<br>
</blockquote></div><br></div>
From 12347ece4b48c81a1db80eec660fc7ec7c542c19 Mon Sep 17 00:00:00 2001 From: Vlad Starodubtsev <v.starodubtsev@ndmsystems.com> Date: Thu, 26 Oct 2017 17:22:33 +0300 Subject: [PATCH] Fix prototypes for preadv pwritev. --- include/sys/uio.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/sys/uio.h b/include/sys/uio.h index 78341ed40..aa766f9b1 100644 --- a/include/sys/uio.h +++ b/include/sys/uio.h @@ -59,7 +59,7 @@ extern ssize_t writev (int __fd, const struct iovec *__iovec, int __count); This function is a cancellation point and therefore not marked with __THROW. */ extern ssize_t preadv (int __fd, const struct iovec *__iovec, int __count, - __off_t __offset) __wur; + off_t __offset) __wur; /* Write data pointed by the buffers described by IOVEC, which is a vector of COUNT 'struct iovec's, to file descriptor FD at the given @@ -71,7 +71,7 @@ extern ssize_t preadv (int __fd, const struct iovec *__iovec, int __count, This function is a cancellation point and therefore not marked with __THROW. */ extern ssize_t pwritev (int __fd, const struct iovec *__iovec, int __count, - __off_t __offset) __wur; + off_t __offset) __wur; #endif /* Use misc. */ __END_DECLS -- 2.17.1
As preadv and pwritev accept off_t type the prototypes should be declared as follows extern ssize_t preadv (int __fd, const struct iovec *__iovec, int __count, off_t __offset) __wur; extern ssize_t pwritev (int __fd, const struct iovec *__iovec, int __count, off_t __offset) __wur; to take into account _FILE_OFFSET_BITS=64 define. I am not sure but probably it is better to redeclare these prototypes by analogy with sendfile using __REDIRECT_NTH.