Date: Mon, 15 Sep 2014 04:29:58 +0000 From: Alexey Dokuchaev <danfe@FreeBSD.org> To: Tijl Coosemans <tijl@FreeBSD.org> Cc: "svn-ports-head@freebsd.org" <svn-ports-head@freebsd.org>, "Jason E. Hale" <jhale@freebsd.org>, "svn-ports-all@freebsd.org" <svn-ports-all@freebsd.org>, ports-committers <ports-committers@freebsd.org> Subject: Re: svn commit: r368130 - in head/devel/bennugd-core: . files Message-ID: <20140915042958.GB15180@FreeBSD.org> In-Reply-To: <20140914112837.375964ab@kalimero.tijl.coosemans.org> References: <201409131920.s8DJKNGP095467@svn.freebsd.org> <CAJE75NEGTy0%2BPNT040Cj7rSinq_DBEDYaJbPzbLTiX=zHp_kEQ@mail.gmail.com> <20140914112837.375964ab@kalimero.tijl.coosemans.org>
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On Sun, Sep 14, 2014 at 11:28:37AM +0200, Tijl Coosemans wrote: > If you ask me it doesn't. The C compiler automatically links in libc > and we used to have two, libc (without threading) and libc_r (with > threading). The -pthread flag told the compiler which one to use. > Nowadays we have one libc and libpthread provides threading functions. > All -pthread does is tell the compiler to link in libpthread, just like > -lpthread does. They are the same. > > It used to be that this libpthread could only be linked into executables > and not into libraries. This meant that if an executable depended on a > library that used threading, it had to be linked with libpthread even if > it didn't use threading itself. This is why several ports still have > LDFLAGS+=-pthread or similar, just because one of the libraries in the > dependency chain used threading. This is no longer necessary. > > There's one thing that is still special about libpthread and that is > that it needs to be loaded into memory before libc because it overrides > some libc symbols. So if you mention -lc explicitly on the command > line (which you normally don't), -lpthread has to appear in front of it. > And, if an executable dlopen()s a library that uses threading, the > executable needs to be linked with libpthread even if it doesn't use > threading itself. Such an awesome explanation must find its way into PHB I think! ./danfe (who is also tired of seeing people patch for -pthread in 2014)
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