Re: Stubdom GMP build failure for gcc 6

From: Juergen Gross <jgross@suse.com>
To: Wei Liu <wei.liu2@citrix.com>,
	Xen-devel <xen-devel@lists.xenproject.org>
Cc: samuel.thibault@ens-lyon.org, xuquan8@huawei.com,
	Ian Jackson <Ian.Jackson@eu.citrix.com>,
	dgdegra@tycho.nsa.gov
Subject: Re: Stubdom GMP build failure for gcc 6
Date: Fri, 28 Oct 2016 16:44:10 +0200	[thread overview]
Message-ID: <72113d2b-153a-80f3-9587-63cea16938de@suse.com> (raw)
In-Reply-To: <20161028121057.GE30231@citrix.com>

On 28/10/16 14:10, Wei Liu wrote:
> Hi all
> 
> There have been a few reports on stubdom build failure with gcc 6
> toolchain. I spent some time yesterday to figure what went wrong. Here
> is what I found.
> 
> When building GMP library, its configure script generates small C
> programs to determine various aspects of the system. Unfortunately the
> build rune for it is incorrect, so the test program ends up consuming
> newlib headers while linking against the host glibc. It's amazing that
> this even worked in the past few years! :-)
> 
> Unfortunately my attempt to fix it by providing LDFLAGS="-nostdlib
> -LXXX" doesn't work. It turns out that there is no crt generated in
> newlib. I'm not sure if that's because the newlib port is incomplete or
> I haven't discovered a way to teach it to generate one.
> 
> So what should we do with this? I'm not sure if I can come up with a
> non-intrusive patch quickly.  GMP is only used by tpm emulator, so for
> the imminent 4.8 release I can write a patch to disable building that.
> 
> Ultimately we need to have a proper solution, because there can be other
> breakages in the future. And I do wish users who need tpm emulator can
> continue to use it. I don't have a clear answer as to how many people
> care about this and how can we fix it.
> 
> Thoughts?

I just tried to verify it is working (or failing) for me. On the machine
I normally did my Xen builds cmake was missing so it never tried to
build libgmp. After installing it I saw the following problem:

at the end of libgmp build:
Libraries have been installed in:
   /home/gross/xen/stubdom/cross-root-x86_64/x86_64-xen-elf/lib64

and when trying to link stubdom-vtpm:
make[2]: Entering directory '/home/gross/xen/extras/mini-os-remote'
ld -r -d -nostdlib
-L/home/gross/xen/stubdom/cross-root-x86_64/x86_64-xen-elf/lib  -m
elf_x86_64 -\( /home/gross/xen/stubdom/vtpm/vtpm.a -T app.lds -\) -ltpm
-ltpm_crypto -lgmp -lpolarssl --undefined main -o
/home/gross/xen/stubdom/mini-os-x86_64-vtpm/mini-os_app.o
ld: cannot find -lgmp

manually adding
"-L/home/gross/xen/stubdom/cross-root-x86_64/x86_64-xen-elf/lib64" lets
the link command succeed.

Juergen

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