There are two approaches to providing system calls and library interfaces that will work with multithreaded programs. One is to simply wrap all the appropriate code with mutexes, thereby guaranteeing that only one thread will execute any such routine at a time.
While this approach mostly works, it provides terrible performance. For functions that maintain state across multiple invocations (e.g. strtok() and friends), this approach simply doesn’t work at all, hence the existence of _r interfaces on many Unix systems (see below).
A better solution is to ensure that library calls can safely be performed by multiple threads at once.
If your Unix system provides threads, it will probably provide a set of thread-safe variants of standard C library routines. A small number of these are mandated by the POSIX standard, and many Unix vendors provide their own useful supersets, including functions such as gethostbyname_r().
Unfortunately, the supersets that different vendors support do not necessarily overlap, so in code that you intend to be portable, you can only safely use the standard POSIX-mandated functions. The thread-safe routines are conceptually “cleaner” than their stateful counterparts, though, so it is good practice to use them wherever and whenever you can.
人気スーパーコピーブランド時計激安通販専門店私達は長年の実体商店の販売経験を持って、先進とプロの技術を持って、高品質のスーパーコピー時計づくりに 取り組んでいます。最高品質のロレックス時計コピー、カルティエ時計コピー、IWC時計コピー、ブライトリング時計コピー、パネライ時計コピー激安販売中商品の数量は多い、品質はよい。海外直営店直接買い付け!★ 2015年注文割引開催中,全部の商品割引10% ★ 在庫情報随時更新! ★ 実物写真、付属品を完備する。 ★ 100%を厳守する。 ★ 送料は無料です(日本全国)!★ お客さんたちも大好評です★ 経営方針: 品質を重視、納期も厳守、信用第一!税関の没収する商品は再度無料にして発送します http://www.okakaku.com/brand-14-copy-0.html