Re: is g++-cxa-atexit.dpatch still needed
Martin,
Have you tried running the orginal test case from
http://gcc.gnu.org/ml/gcc-patches/1999-12n/msg00664.html
with gcc 3.1 built without the g++-cxa-atexit.dpatch.
Both HJ Lu and Jakub Jelinek have been trying to make
clear that since glibc 2.2 the -fuse-cxa-atexit is unnecessary
because __cxa_atexit is no provide through the glibc
atexit call. That is why you can build gcc 3.1 without
the patch and it passes the test case with or without
being compiled with -fuse-cxa-atexit. The patch is totally
uncessary.
Jack
-----------------------------------------------------------
>From hjl@lucon.org Sat Jun 1 22:16:07 2002
Date: Sat, 1 Jun 2002 19:15:36 -0700
From: "H . J . Lu" <hjl@lucon.org>
To: Jack Howarth <howarth@nitro.msbb.uc.edu>
Subject: Re: PATCH: Add --enable-__cxa_atexit
References: <200205310627.CAA13821@nitro.msbb.uc.edu> <200205311604.MAA14609@nitro.msbb.uc.edu> <200205311807.OAA16660@nitro.msbb.uc.edu> <200206020108.VAA20849@nitro.msbb.uc.edu>
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In-Reply-To: <200206020108.VAA20849@nitro.msbb.uc.edu>; from howarth@nitro.msbb.uc.edu on Sat, Jun 01, 2002 at 09:08:54PM -0400
On Sat, Jun 01, 2002 at 09:08:54PM -0400, Jack Howarth wrote:
> HJ,
> I have gone back over the debian mailing list and found
> the origin of their g++-cxa-atexit.dpatch which does...
>
> --- src/gcc/cp/decl2.c~ Wed Jun 6 23:51:11 2001
> +++ src/gcc/cp/decl2.c Sat Jun 23 13:40:36 2001
> @@ -401,7 +401,7 @@
> /* Nonzero to use __cxa_atexit, rather than atexit, to register
> destructors for local statics and global objects. */
>
> -int flag_use_cxa_atexit;
> +int flag_use_cxa_atexit = 1;
>
> /* Nonzero to not ignore namespace std. */
>
> The origin is in...
>
> http://lists.debian.org/debian-gcc/2001/debian-gcc-200106/msg00126.html
> http://gcc.gnu.org/ml/gcc-patches/1999-12n/msg00664.html
>
It isn't needed by the current glibc. I will recommend to drop this
patch from Debian's gcc. I won't apply that patch to my gcc 3.1 nor do
any tests with it.
H.J.
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>From hjl@lucon.org Sat Jun 1 22:24:27 2002
Date: Sat, 1 Jun 2002 19:23:57 -0700
From: "H . J . Lu" <hjl@lucon.org>
To: Jack Howarth <howarth@nitro.msbb.uc.edu>
Subject: Re: debian
References: <200206012132.RAA19767@nitro.msbb.uc.edu>
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In-Reply-To: <200206012132.RAA19767@nitro.msbb.uc.edu>; from howarth@nitro.msbb.uc.edu on Sat, Jun 01, 2002 at 05:32:24PM -0400
On Sat, Jun 01, 2002 at 05:32:24PM -0400, Jack Howarth wrote:
> HJ,
> Debian has just upgraded to gcc 3.1.1-pre1 from the cvs but it seems
> they still have the patch for using __ca_atexit in place. Are you going
> to try a gcc build there with that feature enabled and debug binutils
> to see why the testsuite has the s records failure?
> I ask because the traffic on the gcc mailing list was confused yesterday.
> I got the impression in the end that you had decided to try to help
> regress all use of __ca_atexit out of gcc or was that incorrect? Do other
But Jakub convinced me that Linux doesn't need __ca_atexit from gcc.
I decided not to bother.
> OS's beside linux need that? I know it was claimed that atexit in linux
> was as fast as __ca_atexit but I was unclear if some other OS needed that
> to be retained in gcc. Thanks for any clarification.
Any OS which has __ca_atexit can make its atexit safe. From glibc:
/* This is defined by newer gcc version unique for each module. */
extern void *__dso_handle __attribute__ ((__weak__));
/* Register FUNC to be executed by `exit'. */
int
atexit (void (*func) (void))
{
return __cxa_atexit ((void (*) (void *)) func, NULL,
&__dso_handle == NULL ? NULL : __dso_handle);
}
H.J.
------------------------------------------------------------------------
>From hjl@lucon.org Sat Jun 1 22:43:59 2002
Date: Sat, 1 Jun 2002 19:43:28 -0700
From: "H . J . Lu" <hjl@lucon.org>
To: Jack Howarth <howarth@nitro.msbb.uc.edu>
Subject: Re: PATCH: Add --enable-__cxa_atexit
References: <200205310627.CAA13821@nitro.msbb.uc.edu> <200205311604.MAA14609@nitro.msbb.uc.edu> <200205311807.OAA16660@nitro.msbb.uc.edu> <200206020108.VAA20849@nitro.msbb.uc.edu> <200206020231.WAA21450@nitro.msbb.uc.edu>
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In-Reply-To: <200206020231.WAA21450@nitro.msbb.uc.edu>; from howarth@nitro.msbb.uc.edu on Sat, Jun 01, 2002 at 10:31:46PM -0400
On Sat, Jun 01, 2002 at 10:31:46PM -0400, Jack Howarth wrote:
> patch is totally unnecessary. I am still quite puzzled as to why
> the test case pases with or without -fuse-cxa-atexit and the
> a.out seems to have _use_cxa_atexit in it in both cases. This
> seems to suggest that gcc now detects __cxa_atexit support
No, that __cxa_atexit comes from glibc. When you use atexit, which
gcc 3.1 does, glibc will make sure __cxa_atexit is used. Check out
/usr/lib/libc_nonshared.a and /usr/lib/libc.so. That is why
-fuse-cxa-atexit is useless for Linux, or for any OS which has
__cxa_atexit for that matter.
H.J.
------------------------------------------------------------------------------
Jack W. Howarth, Ph.D. 231 Albert Sabin Way
NMR Facility Director Cincinnati, Ohio 45267-0524
Dept. of Molecular Genetics phone: (513) 558-4420
Univ. of Cincinnati College of Medicine fax: (513) 558-8474
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