FD_SETSIZE在不同操作系统中的行为(From Squid)

1、LINUX下面
Cannot increase FD_SETSIZE on Linux, but we can increase __FD_SETSIZE
with glibc 2.2 (or later? remains to be seen). We do this by including
bits/types.h which defines __FD_SETSIZE first, then we redefine
__FD_SETSIZE. Ofcourse a user program may NEVER include bits/whatever.h
directly, so this is a dirty hack!

#if (__GLIBC__ > 2) || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 2)
#include
#undef __FD_SETSIZE
#define __FD_SETSIZE SQUID_MAXFD
#endif

2、FreeBsd

Cannot increase FD_SETSIZE on FreeBSD before 2.2.0, causes select(2)
to return EINVAL.

3、Mac OS X Server

Trying to redefine CHANGE_FD_SETSIZE causes a slew of warnings
on Mac OS X Server.

其他的大部分平台基本上都可以重定义FD_SETSIZE（当然包括winnt系列了)

 

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