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