From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id 2DFD23858C5F; Fri, 26 May 2023 20:25:49 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 2DFD23858C5F
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1685132749;
	bh=ivnnlx4O3teBoMiDuZFULRXlzllDYhJ8P1walm+wknE=;
	h=From:To:Subject:Date:From;
	b=BVRrraZ+fmL1KJ2oWcLsRdfY9VgBfVbFXoloAuhI1/zL9yuYwhF8LcuBbAYjG4bKR
	 nTFbzXHraKzD8uJ2y26LC3F/INRdr5nBtGbpca2gtQ6vjp/XjI/hIvxbn8Dx88N8fE
	 Xy+suJaDggA88ioIqU+tK33kyObnRkblSMUUix1A=
From: "nikolasklauser at berlin dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/110000] New: GCC should implement
 exclude_from_explicit_instantiation
Date: Fri, 26 May 2023 20:25:48 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: unknown
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: nikolasklauser at berlin dot de
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-110000-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110000

            Bug ID: 110000
           Summary: GCC should implement
                    exclude_from_explicit_instantiation
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nikolasklauser at berlin dot de
  Target Milestone: ---

`exclude_from_explicit_instantiation` is an attribute implemented by clang.=
 It
tells the compiler that a function should not be part of an explicit
instantiation. This allows libraries to have greater control over which
functions are part of their ABI and which aren't. It is used extensively in
libc++ to keep the ABI surface as small as possible. Currently, libc++ uses
always_inline if exclude_from_explicit_instantiation isn't available, resul=
ting
in almost every function in the library being declared as always_inline.
Replacing always_inline with exclude_from_explicit_instantiation would
approximately halve the time it takes to run the libc++ test suite with GCC.
(removing always_inline brings the time down to about the same as clang tak=
es)=