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 &lt;wbx(a)uclibc-ng.org&gt; wrote: