Re: Thread configure flag

Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> Bruce Momjian writes:
>> If it is the default, libpq is going to use the libc_r library, at least
>> on some platforms, and that may not be desired.

> But what is the objective reason for this lack of desire?

I have heard that the reentrant libc is significantly worse-performing
than the non-reentrant one on some platforms. This is not real hard
to believe, since functions as common as malloc() will need locking
overhead if they think they might be in a multithreaded environment.

However, that's only an argument that we must provide a
--without-threads option, it doesn't speak strongly to the question of
what the default choice should be (where there is a choice).

> _POSIX_PTHREAD_SEMANTICS isn't used anywhere in the entire system, the
> effect of _THREAD_SAFE is to define _REENTRANT, and the effect of
> _REENTRANT is to declare getlogin_r(), which PostgreSQL sources don't use.

On which version of Linux are the above statements true? Are you sure
they are true on other versions?

regards, tom lane