__USE_FILE_OFFSET64与_FILE_OFFSET_BITS = 64 [英] __USE_FILE_OFFSET64 vs. _FILE_OFFSET_BITS=64

问题描述

我试图维护在许多不同系统上编译的代码。我看过十几种不同的方式来询问需要64位的 lseek 。一些系统使用 lseek64 ，有些使用 lseeko ，有些需要定义 _FILE_OFFSET_BITS = 64 ，现在我找到一个新的，需要你定义 __ USE_FILE_OFFSET64 。

I am trying to maintain code that compiles on lots of different systems. I've seen a dozen different ways of asking for lseek that takes 64-bits. Some systems use lseek64, some use lseeko, some require that you define _FILE_OFFSET_BITS=64, and now I just found a new one that requires that you define __USE_FILE_OFFSET64.

这是否有任何标准？

推荐答案

有 IEEE Std 1003.1-2004中的getconf值（以及 IEEE Std 1003.1-2008 ;也参见这些文献中的实施例部分）。

There are getconf values in IEEE Std 1003.1-2004 (and a newer set in IEEE Std 1003.1-2008; see also the EXAMPLES section in those documents). Actual compiler options (which might not even be defines) are not specified.

但是，autoconf中的 AC_SYS_LARGEFILE 宏不会指定实际的编译器选项不尝试使用它 - 它尝试只是 -n32 为IRIX， -D_FILE_OFFSET_BITS = 64 （这应该工作大多数系统）和 -D_LARGE_FILES = 1 （显然对于AIX）。还可以参考向单个UNIX规范添加对任意文件大小的支持<

However, the AC_SYS_LARGEFILE macro in autoconf does not try to use this — it tries just -n32 for IRIX, -D_FILE_OFFSET_BITS=64 (which should work for most systems) and -D_LARGE_FILES=1 (apparently for AIX). There is also a reference to Adding Support for Arbitrary File Sizes to the Single UNIX Specification (an older spec draft which was then partially included in the POSIX.1 spec) in autoconf sources.

至于定义 __ USE_FILE_OFFSET64

As for defining __USE_FILE_OFFSET64 manually, not sure if this is really a correct solution — double-underscore macros are reserved for system headers, and most likely there is some conditional definition there which depends on other defines.

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