From mboxrd@z Thu Jan  1 00:00:00 1970
From: Danny Milosavljevic <dannym@scratchpost.org>
Subject: Re: [PATCH] gnu: Add LDFLAGS=-lpthread to configure-flags where
	needed.
Date: Tue, 21 Mar 2017 12:29:05 +0100
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References: <1490059331-32049-1-git-send-email-john@darrington.wattle.id.au>
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To: John Darrington <john@darrington.wattle.id.au>
Cc: guix-devel@gnu.org

Hi John,

thanks for looking into the problem.

On Tue, 21 Mar 2017 02:22:11 +0100
John Darrington <john@darrington.wattle.id.au> wrote:
> +   (arguments `(#:configure-flags '("LDFLAGS=-lpthread")))

Hmm, that seems to be a very unsafe thing to do.

In order to actually use pthread, one has to switch gcc into pthread mode (which influences how it handles variables etc).
But just passing "-lpthread" to the linker does no such things and will only make it link - with the wrong actual instructions in the object files!

Also, even if it worked - by chance -, that seems like papering over the problem.

It would be better to check out the object files (with objdump -r or objdump -t) and find out where the symbol is listed as undefined ("U"). Then check the associated source file whether it actually intended to use pthread.

Pthread is not exactly a modular library that you can just switch on and off at will.