> Then it needs to sort them if there is more than one address. And in order to do that it needs to read /etc/gai.conf

I don’t see why glibc would have to do that inside a call to getaddrinfo. can’t it do that once at library initialization? If it has to react to changes to that file while a process is running, couldn’t it have a separate thread for polling that file for changes, or use inotify for a separate thread to be called when it changes? Swapping in the new config atomically might be problematic, but I would think that is solvable.

Even ignoring the issue mentioned it seems wasteful to open, parse, and close that file repeatedly.

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loeg 3 days ago | parent | next [-]

I think the libc people might argue this level of functionality is just outside the scope of libc. (Arguably, it is a mistake for DNS to be part of libc, given how complicated it is.)

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Someone 8 hours ago | parent | next [-]

https://sourceware.org/glibc/ says

“The GNU C Library is designed to be a backwards compatible, portable, and high performance ISO C library. It aims to follow all relevant standards including ISO C11, POSIX.1-2008, and IEEE 754-2008.”

⇒ I don’t think they make that argument.

	▲	loeg 2 hours ago \| parent [-]
		The standards make no requirement that an implementation be good, performant, or even useful.

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ComputerGuru 3 days ago | parent | prev [-]

To be sure, complexity isn’t the determinator for whether something is or isn’t in scope for libc though.

	▲	loeg 3 days ago \| parent [-]
		Historically libcs have been leery of imposing threading on otherwise singlethreaded applications; and for similar reasons, try to minimize startup costs.

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cesarb 3 days ago | parent | prev | next [-]

> I don’t see why glibc would have to do that inside a call to getaddrinfo. can’t it do that once at library initialization?

If it were a library dedicated to DNS, sure, but glibc is used by nearly every process in the system, including many which will never call getaddrinfo.

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NewJazz 3 days ago | parent | prev [-]

You want libc to start a thread whenever it is loaded?

	▲	Someone 3 days ago \| parent [-]
		If it’s the only alternative to being broken: yes. It could read and parse the file the first time a thread gets created, too. A cheaper alternative is to check the modification time of the config file, and only reparse it in pthread_cancel when that changes. That doesn’t 10% fix the problem in theory, but would do it in practice.