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>
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