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Asked: 2026-05-28T13:01:10+00:00

While reading up on POSIX threading, I came across an example of thread-specific-data. I

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While reading up on POSIX threading, I came across an example of thread-specific-data. I did have one area of confusion in my mind…

The thread-specific-data interface looks a little clunky, especially once you mix in having to use pthread_once, the various initializers, etc.

Is there any reason I can’t just use a static std::map where the key is the pthread_self() id and the data value is held in the second part of the std::pair?

I can’t think of a reason that this wouldn’t work as long as it was wrapped in a mutex, but I see no suggestion of it or anything similar which confuses me given it sounds much easier than the provided API. I know threading can have alot of catch-22’s so I thought I’d ask and see if I was about to step in… something unpleasant? 🙂

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  1. Editorial Team

    I can’t think of a reason that this wouldn’t work as long as it was wrapped in a mutex

    That in itself is a very good reason; implemented properly, you can access your thread-specific data without preventing other threads from simultaneously creating or accessing theirs.

    There’s also general efficiency (constant time access, versus logarithmic time if you use std::map), no guarantee that pthread_t has a suitable ordering defined, and automatic cleanup along with all the other thread resources.

    You could use C++11’s thread_local keyword, or boost::thread_specific_ptr, if you don’t like the Posix API.

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