Problem building GDB on Power64

Problem building GDB on Power64

[Paul Gilliam]

On a ppc64 system, GDB builds as a 32-bit application.  This is OK if the 
64-bit dev. env. is not available.  But if it is, this is wrong: GDB should 
build as a 64-bit application so that both 64 and 32 bit apps can be 
debugged.

If I understood the configure process, I would have tried submitting a patch.  
It should be easy: just include -m64 in the CFLAGS.  And make sure to link 
with the 64-bit libraries (which had better be there).

-=# Paul Gilliam #=-

Re: Problem building GDB on Power64

[Daniel Jacobowitz]

On Thu, Sep 02, 2004 at 09:20:53AM -0700, Paul Gilliam wrote:
> On a ppc64 system, GDB builds as a 32-bit application.  This is OK if the 
> 64-bit dev. env. is not available.  But if it is, this is wrong: GDB should 
> build as a 64-bit application so that both 64 and 32 bit apps can be 
> debugged.
> 
> If I understood the configure process, I would have tried submitting a patch.  
> It should be easy: just include -m64 in the CFLAGS.  And make sure to link 
> with the 64-bit libraries (which had better be there).

IMO, if your 64-bit environment defaults to building 32-bit code, it's
your responsibility to set -m64 yourself.

-- 
Daniel Jacobowitz

Re: Problem building GDB on Power64

[Paul Gilliam]

On Thursday 02 September 2004 10:21, Daniel Jacobowitz wrote:
> On Thu, Sep 02, 2004 at 09:20:53AM -0700, Paul Gilliam wrote:
> > On a ppc64 system, GDB builds as a 32-bit application.  This is OK if the
> > 64-bit dev. env. is not available.  But if it is, this is wrong: GDB
> > should build as a 64-bit application so that both 64 and 32 bit apps can
> > be debugged.
> >
> > If I understood the configure process, I would have tried submitting a
> > patch. It should be easy: just include -m64 in the CFLAGS.  And make sure
> > to link with the 64-bit libraries (which had better be there).
>
> IMO, if your 64-bit environment defaults to building 32-bit code, it's
> your responsibility to set -m64 yourself.

Normally I would agree with you, but this is kind of a special case.

The reason the 64-bit environment defaults to building 32-bit code is that it 
was felt that most applications running on a 64-bit processor will be 32-bit 
applications. (at least that's what the gcc person in the next cube explained 
to me).

But, if possible, the debugger should handle either.  In fact, the gdb 
installed with the 64-bit dev. system is a 64-bit app. and can debug both 64 
and 32 bit apps.

In this case, then, I think it makes more sense for gdb to build atomaticly as 
a 64-bit app, if it can be.

-=# Paul #=-

PS:  I'm not asking for someone to post patches to configure.in or what ever, 
(hinting maybe), but I am asking for some pointers on where to look.

Re: Problem building GDB on Power64

[Daniel Jacobowitz]

On Thu, Sep 02, 2004 at 10:52:04AM -0700, Paul Gilliam wrote:
> On Thursday 02 September 2004 10:21, Daniel Jacobowitz wrote:
> > On Thu, Sep 02, 2004 at 09:20:53AM -0700, Paul Gilliam wrote:
> > > On a ppc64 system, GDB builds as a 32-bit application.  This is OK if the
> > > 64-bit dev. env. is not available.  But if it is, this is wrong: GDB
> > > should build as a 64-bit application so that both 64 and 32 bit apps can
> > > be debugged.
> > >
> > > If I understood the configure process, I would have tried submitting a
> > > patch. It should be easy: just include -m64 in the CFLAGS.  And make sure
> > > to link with the 64-bit libraries (which had better be there).
> >
> > IMO, if your 64-bit environment defaults to building 32-bit code, it's
> > your responsibility to set -m64 yourself.
> 
> Normally I would agree with you, but this is kind of a special case.
> 
> The reason the 64-bit environment defaults to building 32-bit code is that it 
> was felt that most applications running on a 64-bit processor will be 32-bit 
> applications. (at least that's what the gcc person in the next cube explained 
> to me).
> 
> But, if possible, the debugger should handle either.  In fact, the gdb 
> installed with the 64-bit dev. system is a 64-bit app. and can debug both 64 
> and 32 bit apps.
> 
> In this case, then, I think it makes more sense for gdb to build atomaticly as 
> a 64-bit app, if it can be.

I really don't agree - I think it's the packager's or builder's job to do this.

> PS:  I'm not asking for someone to post patches to configure.in or what ever, 
> (hinting maybe), but I am asking for some pointers on where to look.

This would be very tricky to do.  GDB links to libraries built in the
same tree, so nothing in gdb/configure.in would work.  It would have to
be in the top level, which is shared with binutils and gcc and so on. 
You don't want them to default to being 64-bit apps, because they
should obey the system policy of defaulting to 32-bit.

I really think this is your responsibility when building GDB if you
want it to support 64-bit binaries.

-- 
Daniel Jacobowitz

Re: Problem building GDB on Power64

[Andrew Cagney]

>>> PS:  I'm not asking for someone to post patches to configure.in or what ever, 
>>> (hinting maybe), but I am asking for some pointers on where to look.
> 
> 
> This would be very tricky to do.  GDB links to libraries built in the
> same tree, so nothing in gdb/configure.in would work.  It would have to
> be in the top level, which is shared with binutils and gcc and so on. 
> You don't want them to default to being 64-bit apps, because they
> should obey the system policy of defaulting to 32-bit.
> 
> I really think this is your responsibility when building GDB if you
> want it to support 64-bit binaries.

Exactly.

GDB's build behavior is determined by policies set by autotools, config 
and <top-level>.  GDB isn't in a position to vary this locally. 
Perhaphs the thing to do is rase this on GCC (where I'd guess the 
<top-level> aspect should be discussed).

BTW, I did once ask to the config maintainer (BJE@ibm) if config.guess 
could look at the compiler.  That way, instead of:
	$ CC='cc -m64' config.guess
	powerpc-unknown-linux-gnu
it would return:
	$ CC='cc -m64' config.guess
	powerpc64-unknown-linux-gnu
and that in turn would let us specify:
	$ CC='cc -m64' .../configure
Ben didn't agree (I don't remember why).

Andrew

Re: Problem building GDB on Power64

[Michael Chastain]

Here's an idea from gcc:

gcc has a directory named INSTALL with a file 'specific.html', which has
info organized by target.  If we had a file like that, then that would
be the natural place for describing build choices like -m32 and -m64.

It would also be a good place for the section of PROBLEMS that
are about build failures and their workarounds.

I'm not strongly pounding the table for this, just pointing it out.
What do y'all think?

Michael

Re: Problem building GDB on Power64

[Eli Zaretskii]

> Date: Thu, 02 Sep 2004 16:16:58 -0400
> From: Michael Chastain <mec.gnu@mindspring.com>
> Cc: gdb@sources.redhat.com, drow@false.org
> 
> Here's an idea from gcc:
> 
> gcc has a directory named INSTALL with a file 'specific.html', which has
> info organized by target.  If we had a file like that, then that would
> be the natural place for describing build choices like -m32 and -m64.
> 
> It would also be a good place for the section of PROBLEMS that
> are about build failures and their workarounds.

I think PROBLEMS is the wrong place for this, unless there's a small
number of platforms with specific build problems.

Why not put this in the INSTALL file?  That's where installation
instructions belong, IMHO.