gcc 4.2 dump problems

gcc 4.2 dump problems

[David Reitter]

It turns out that you can't build Emacs with gcc 4.2 on Macs, and gcc  
4.2 is probably the compiler of choice for the upcoming OS X version.   
The new gcc version is not the only problem, but it seems that using  
gcc 4.2 on any version of OS X will reproduce the issue.

I don't suppose people have problems with 4.2 on non-Mach-O object  
file architectures?

http://emacsbugs.donarmstrong.com/cgi-bin/bugreport.cgi?bug=3708

Any comments regarding this bug from knowledgeable people?

Re: gcc 4.2 dump problems

[Werner LEMBERG]

> It turns out that you can't build Emacs with gcc 4.2 on Macs, and
> gcc 4.2 is probably the compiler of choice for the upcoming OS X
> version.  The new gcc version is not the only problem, but it seems
> that using gcc 4.2 on any version of OS X will reproduce the issue.

BTW, gcc 4.2 can't build the current CVS version of groff either, while
version 4.3.2 can...


    Werner

Re: gcc 4.2 dump problems

[Dan Nicolaescu]

David Reitter <david.reitter@gmail.com> writes:

  > It turns out that you can't build Emacs with gcc 4.2 on Macs, and gcc
  > 4.2 is probably the compiler of choice for the upcoming OS X version.
  > The new gcc version is not the only problem, but it seems that using
  > gcc 4.2 on any version of OS X will reproduce the issue.
  > 
  > I don't suppose people have problems with 4.2 on non-Mach-O object
  > file architectures?

I don't use gcc-4.2 anymore, but I've never seen such problems with it
on GNU/Linux while using it.

How did you determine that gcc-4.2 is the problem?

Did you try different versions of gcc on the same machine, keeping the
same version of binutils, and only gcc-4.2 had problems?

Have you tried compiling with -O0 ?  Did you also have problems when using -O0 ?

Re: gcc 4.2 dump problems

[David Reitter]

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On Aug 6, 2009, at 2:24 PM, Dan Nicolaescu wrote:
> I don't use gcc-4.2 anymore, but I've never seen such problems with it
> on GNU/Linux while using it.
>
> How did you determine that gcc-4.2 is the problem?

See Ian Eure's post to bug 3708 for this.  He installed GCC 4.2 on a  
10.5 machine and obtained similar results.
The error messages differ at times, but they do that on the 10.6  
machine that I tried it on, too.
(Building with 4.0 on 10.5 works fine.)

> Did you try different versions of gcc on the same machine, keeping the
> same version of binutils, and only gcc-4.2 had problems?

Ian, from your message, it looks like this is what you did, right?

> Have you tried compiling with -O0 ?  Did you also have problems when  
> using -O0 ?

Yes, I use -O0 routinely, including in the bug report.



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Re: gcc 4.2 dump problems

[Dan Nicolaescu]

David Reitter <david.reitter@gmail.com> writes:

  > On Aug 6, 2009, at 2:24 PM, Dan Nicolaescu wrote:
  > > I don't use gcc-4.2 anymore, but I've never seen such problems with it
  > > on GNU/Linux while using it.
  > >
  > > How did you determine that gcc-4.2 is the problem?
  > 
  > See Ian Eure's post to bug 3708 for this.  He installed GCC 4.2 on a
  > 10.5 machine and obtained similar results.

Sorry, there's too much noise in that bug, and from what I can see what
is there, it does not point to the fact that gcc-4.2 is the problem:

CFLAGS='-g -O0' CC=gcc-4.0 ./configure --without-ns --without-x
[snip]
dump failure.

So can you please summarize the info and try to go step by step:

1. find out if you find a machine where you have gcc-4.2 failing and
some other version of gcc working.
2. make sure that when using the 2 versions of gcc above only the
compiler is different, not the rest of the tools: assembler, linker, or
any libraries
3. if you have non-gcc-4.2 working, compile with it, remove temacs and
then link the same object files with gcc-4.2 and see if that works

Depending what you get above we can figure out what to do next.

Do not assume that people on this list are familiar with macs, or what
various commands to install packages actually do

Re: gcc 4.2 dump problems

[David Engster]

I'm reviving this old thread, since I'm now facing the same problem with
the arrival of Mac OS X 10.6...

David Reitter <david.reitter@gmail.com> writes:
> On Aug 6, 2009, at 2:24 PM, Dan Nicolaescu wrote:
>> I don't use gcc-4.2 anymore, but I've never seen such problems with it
>> on GNU/Linux while using it.
>>
>> How did you determine that gcc-4.2 is the problem?
>
> See Ian Eure's post to bug 3708 for this.  He installed GCC 4.2 on a
> 10.5 machine and obtained similar results.
> The error messages differ at times, but they do that on the 10.6
> machine that I tried it on, too.
> (Building with 4.0 on 10.5 works fine.)

I consistently get the same error on 10.6, and it's the one with 

unexec: unrecognized section name in __DATA segment

This unrecognized section in the DATA segment is called
"__program_vars", and I cannot find any documentation for it. It's not
mentioned in the Mach-O File Format Reference at all, even in the latest
XCode I installed from the Developer Connection.

So my guess is that unexecmacosx.c has to be patched to deal correctly
with that section. I don't know the first thing about this dumping
process, but I simply tried to include it in the section where
__la_symbol_ptr and __nl_symbol_ptr are handled, and it didn't work...

-David

Re: gcc 4.2 dump problems

[Ian Eure]

On Aug 25, 2009, at 6:18 AM, David Engster wrote:

> I'm reviving this old thread, since I'm now facing the same problem  
> with
> the arrival of Mac OS X 10.6...
>
Perhaps you can install MacPorts and the apple-gcc40 port as a  
temporary workaround.

  - Ian

Re: gcc 4.2 dump problems

[David Reitter]

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On Aug 25, 2009, at 11:56 AM, Ian Eure wrote:
>> I'm reviving this old thread, since I'm now facing the same problem  
>> with
>> the arrival of Mac OS X 10.6...
>>
> Perhaps you can install MacPorts and the apple-gcc40 port as a  
> temporary workaround.

Anyone, please post if you've been successful.  I have tried this a  
while ago with "i686-apple-darwin10-gcc-4.0.1", but perhaps I didn't  
pick the right compiler+linker settings.

Thankfully, Dan N has been looking into this - some info below.  I  
haven't found any info on this new link format - pointers appreciated.

Dan Nicolaescu wrote:

>
> On Snow Leopard:
> It looks like dumper in emacs does not understand the new compact link
> edit format in Snow Leopard.  (Long term someone needs to reword
> unexecmacosx.c to deal with that)
>
> Unfortunately workarounds to not use that format like:
> -mmacosx-version-min=10.4
> or
> -mmacosx-version-min=10.5 -Wl,-no_compact_linkedit
>
> don't seem to help either.
>
> I'll let you know if I find out more.

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Re: gcc 4.2 dump problems

[David Engster]

Ian Eure <ian@digg.com> writes:
> On Aug 25, 2009, at 6:18 AM, David Engster wrote:
>
>> I'm reviving this old thread, since I'm now facing the same problem
>> with
>> the arrival of Mac OS X 10.6...
>>
> Perhaps you can install MacPorts and the apple-gcc40 port as a
> temporary workaround.

That doesn't work, either.

I could not build any other gcc via macports on 10.6, so I compiled gcc
4.2 manually, but that also didn't help. While I do not get the
__program_vars section in the __DATA segment anymore, the resulting dump
now crashes.

-David