[m-dev.] test server

[Zoltan Somogyi]

On Mon, 31 Mar 2025 14:15:26 +1100, Peter Wang <novalazy at gmail.com> wrote:

> On Mon, 31 Mar 2025 12:42:29 +1100 "Zoltan Somogyi" <zoltan.somogyi at runbox.com> wrote:
> > 
> > 
> > On Mon, 31 Mar 2025 12:21:54 +1100, Peter Wang <novalazy at gmail.com> wrote:
> > 
> > > Hi, we have set up a new test server at:
> > > 
> > >     http://172.236.33.24
> > > 
> > > Configuration: 2 virtual cores, 4 GB RAM, running Ubuntu Linux 24.04.
> > > 
> > > vendor_id	: AuthenticAMD
> > > cpu family	: 25
> > > model		: 1
> > > model name	: AMD EPYC 7713 64-Core Processor
> > > stepping	: 1
> > 
> > Thank you very much. Can you, or Julien, please point
> > testing.mercurylang.org at it?
> > 
> > I note that there seems to be an issue with a warning from
> > compiling Boehm gc. Does anyone know the root cause for that is?
> 
> The full warning message is:
> 
> /usr/bin/ld: warning: atomic_ops_sysdeps.o: missing .note.GNU-stack section implies executable stack
> /usr/bin/ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
> 
> It seems that old versions of GNU ld defaulted to an executable stack,
> while newer versions of GNU ld warn about depending on that default.
> To suppress the warning, we would pass -z noexecstack to the linker at
> the correct places, but I haven't tried it yet.

The file boehm_gc/libatomic_ops/src/atomic_ops_sysdeps.S, which in my workspace
is the only possible source for the .o file the linker is complaining about, is effectively
an empty file on non-SPARC systems, i.e. on all the systems that we use, AFAIK.
Instead of telling ld to use an executable stack, we could

- add the missing .note.GNU-stack section to atomic_ops_sysdeps.S,
  provided Boehm does not actually need executable stacks on SPARCs
  (which I think is likely),

- if Boehm does need executable stacks on SPARCs, we could add a
  dummy definition to a new else arm of the #ifdef in that file,
  which should fix the issue on non-SPARC systems if the only reason
  for the warning is that ld is complaining about the *empty* .o file
  missing that section, or

- we could modify the makefile to include atomic_ops_sysdeps.S among
  the list of source modules only if the condition of the #ifdef is true.
  There is already a flag for that, NEED_ASM, but I don't see why its value
  calls for the inclusion of atomic_ops_sysdeps.S; configure.ac should set it
  only on Solaris hosts. But then, I have never used automake, so my reading
  of Makefile.am is superficial.

In general, we should ask ld to provide an executable stack only if Boehm
actually needs one.

Zoltan.