Re: BoF DWARF5 patches (25% .debug section size reduction)

[Mark Wielaard <mark@klomp.org>]

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On Thu, 2020-09-10 at 13:16 +0200, Jakub Jelinek wrote:
> On Wed, Sep 09, 2020 at 09:57:54PM +0200, Mark Wielaard wrote:
> > --- a/gcc/doc/invoke.texi
> > +++ b/gcc/doc/invoke.texi
> > @@ -9057,13 +9057,14 @@ possible.
> >  @opindex gdwarf
> >  Produce debugging information in DWARF format (if that is supported).
> >  The value of @var{version} may be either 2, 3, 4 or 5; the default version
> > -for most targets is 4.  DWARF Version 5 is only experimental.
> > +for most targets is 5 (with the exception of vxworks and darwin which
> > +default to version 2).
> 
> I think in documentation we should spell these VxWorks and Darwin/Mac OS X

OK. As attached.

Are we ready to flip the default to 5?

Thanks,

Mark

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From 409bd1b2c60905b0f96c94fface12154d3be4d32 Mon Sep 17 00:00:00 2001
From: Mark Wielaard <mark@klomp.org>
Date: Tue, 29 Sep 2020 15:52:44 +0200
Subject: [PATCH] Default to DWARF5

gcc/ChangeLog:

	* common.opt (gdwarf-): Init(5).
	* doc/invoke.texi (-gdwarf): Document default to 5.
---
 gcc/common.opt      | 2 +-
 gcc/doc/invoke.texi | 7 ++++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/gcc/common.opt b/gcc/common.opt
index 292c2de694ef..d1722de80bf0 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -3148,7 +3148,7 @@ Common Driver JoinedOrMissing Negative(gdwarf-)
 Generate debug information in default version of DWARF format.
 
 gdwarf-
-Common Driver Joined UInteger Var(dwarf_version) Init(4) Negative(gstabs)
+Common Driver Joined UInteger Var(dwarf_version) Init(5) Negative(gstabs)
 Generate debug information in DWARF v2 (or later) format.
 
 ggdb
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 2091e0cd23b9..e6453374bcd4 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -9210,14 +9210,15 @@ possible.
 @itemx -gdwarf-@var{version}
 @opindex gdwarf
 Produce debugging information in DWARF format (if that is supported).
-The value of @var{version} may be either 2, 3, 4 or 5; the default version
-for most targets is 4.  DWARF Version 5 is only experimental.
+The value of @var{version} may be either 2, 3, 4 or 5; the default
+version for most targets is 5 (with the exception of VxWorks and
+Darwin/Mac OS X which default to version 2).
 
 Note that with DWARF Version 2, some ports require and always
 use some non-conflicting DWARF 3 extensions in the unwind tables.
 
 Version 4 may require GDB 7.0 and @option{-fvar-tracking-assignments}
-for maximum benefit.
+for maximum benefit. Version 5 requires GDB 8.0 or higher.
 
 GCC no longer supports DWARF Version 1, which is substantially
 different than Version 2 and later.  For historical reasons, some
-- 
2.18.4