如何使lseek64 _ Actally_返回64位偏移?
-
23-10-2019 - |
题
#define _FILE_OFFSET_BITS 64
#define _LARGEFILE64_SOURCE
...
off64_t st_size;
...
st_size = (off64_t)lseek64(fd, (off64_t)0, SEEK_END);
fprintf(stderr, "QQQ st_size=%llx %lld\n", st_size, st_size);
然后Strace:
$ strace -e _llseek ./the_program
_llseek(3, 0, [20974464000], SEEK_END) = 0
QQQ st_size=ffffffffe22cec00 -500372480
- 20974464000 == 0x4e22cec00-好
- -500372480 == 0xffffffffffe22cec00-不好
它变为 (off64_t)lseek64(fd, 0, SEEK_END);
它不正确地调用_llseek:
_llseek(3, 8589934592, [8589934592], SEEK_SET) = 0
st_size=0 0
我还应该做些什么来确保它正确地达到尺寸,而不会砍掉主要的dword?
解决方案
确保您定义 _FILE_OFFSET_BITS
和 _LARGEFILE64_SOURCE
前 包括sys/types.h和unistd.h。最好在编译器的命令行中。
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