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From: "ian at airs dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug go/113143] Remove usage of ucontext.h
Date: Wed, 27 Dec 2023 23:20:57 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113143

--- Comment #10 from Ian Lance Taylor <ian at airs dot com> ---
The makecontext/getcontext/setcontext functions are called by libgo on
GNU/Linux for all targets other than x86_64.  It is not the case that they =
are
used only on *BSD systems.

The default gc implementation does not require these functions because it
provides assembler code.  This of course limits the gc implementation to on=
ly
support a limited number of targets: those for which the assembler code exi=
sts.
 libgo is intended to be more portable.

To be clear I am fine with removing or guarding references to ucontext.h wh=
ere
that makes sense.  I'm just pointing out that the code can't in general wor=
k if
the *context functions are not available.  It's unfortunate that POSIX remo=
ved
them without providing adequate replacements.  Saying that they "can be
replaced using POSIX threads functions" is simply false.  They provide a
portable mechanism for a userspace threads mechanism on top of POSIX thread=
s.=20
Without them there is no way for libgo to implement goroutines efficiently.=