diff mbox

[1/8] libunwind: fix C library dependency

Message ID 1453148701-10036-2-git-send-email-thomas.petazzoni@free-electrons.com
State Superseded
Headers show

Commit Message

Thomas Petazzoni Jan. 18, 2016, 8:24 p.m. UTC 
The libunwind package currently dependency on glibc *or* uclibc
snapshot. However, we are going to remove the support for uclibc
snapshot, and uClibc-ng has equivalent functionality as uclibc
snapshot. Moreover, musl is also capable of building libunwind for
certain architectures.

Therefore, this commit reworks the architecture dependencies of
libunwind, to make it available on all architectures for which it is
supported, depending on the capabilities of the different C libraries,
and the implementation of libunwind on each architecture.

On some architectures, libunwind uses the C library *context()
functions, which are not provided by musl at all, and not provided by
uClibc on all architectures. But on some other architectures,
libunwind does not use the C library *context() functions, which
explains why it can be built with musl on such architectures.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
---
 package/libunwind/Config.in | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

Comments

Romain Naour Jan. 25, 2016, 9:59 p.m. UTC | #1 
Hi Thomas, All,

Le 18/01/2016 21:24, Thomas Petazzoni a écrit :
> The libunwind package currently dependency on glibc *or* uclibc
> snapshot. However, we are going to remove the support for uclibc
> snapshot, and uClibc-ng has equivalent functionality as uclibc
> snapshot. Moreover, musl is also capable of building libunwind for
> certain architectures.
> 
> Therefore, this commit reworks the architecture dependencies of
> libunwind, to make it available on all architectures for which it is
> supported, depending on the capabilities of the different C libraries,
> and the implementation of libunwind on each architecture.
> 
> On some architectures, libunwind uses the C library *context()
> functions, which are not provided by musl at all, and not provided by
> uClibc on all architectures. But on some other architectures,
> libunwind does not use the C library *context() functions, which
> explains why it can be built with musl on such architectures.
> 
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> ---
>  package/libunwind/Config.in | 31 ++++++++++++++++++++++++-------
>  1 file changed, 24 insertions(+), 7 deletions(-)
> 
> diff --git a/package/libunwind/Config.in b/package/libunwind/Config.in
> index 85cb472..6f747ae 100644
> --- a/package/libunwind/Config.in
> +++ b/package/libunwind/Config.in
> @@ -1,15 +1,32 @@
> +# libunwind is only available for a certain subset of the
> +# architectures (as visible in the list of architectures supported
> +# with the glibc C library below).
> +#
> +# In addition to this, on some architectures libunwind requires the
> +# *context() function from the C library, which are only available on
> +# certain architectures in uClibc, and not available at all on
> +# musl. But on some other architectures, libunwind works without using
> +# the *context() functions, which allows it to be built with musl.
> +config BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS
> +	bool
> +	default y if BR2_TOOLCHAIN_USES_GLIBC && \
> +		(BR2_arm || BR2_armeb || BR2_mips || BR2_mipsel || BR2_mips64 || \
> +		 BR2_mips64el || BR2_powerpc || BR2_sh || BR2_sh64 || BR2_i386 || BR2_x86_64)
> +	default y if BR2_TOOLCHAIN_USES_UCLIBC && \
> +		(BR2_arm || BR2_armeb || BR2_i386 || BR2_mips || BR2_mipsel || \
> +		 BR2_x86_64)
> +	default y if BR2_TOOLCHAIN_USES_MUSL && \
> +		(BR2_arm || BR2_armeb || BR2_i386 || BR2_x86_64)
> +
>  config BR2_PACKAGE_LIBUNWIND
>  	bool "libunwind"
>  	depends on BR2_TOOLCHAIN_HAS_THREADS
> -	depends on (BR2_UCLIBC_VERSION_SNAPSHOT || BR2_TOOLCHAIN_USES_GLIBC) # {g,s}etcontext
> -	depends on BR2_arm || BR2_armeb || BR2_mips || BR2_mipsel || BR2_mips64 || \
> -		BR2_mips64el || BR2_powerpc || BR2_sh || BR2_sh64 || BR2_i386 || BR2_x86_64
> +	depends on BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS

Build tested on musl and x86_64.
Checked that libunwind doesn't build with uClibc-snapshot and uClibc-ng.

Reviewed-by: Romain Naour <romain.naour@gmail.com>

Best regards,
Romain

>  	help
>  	  C API to determine the call-chain of a program.
>  
>  	  http://www.nongnu.org/libunwind/index.html
>  
> -comment "libunwind needs a uclibc snapshot or (e)glibc toolchain w/ threads"
> -	depends on BR2_arm || BR2_armeb || BR2_mips || BR2_mipsel || BR2_mips64 || \
> -		BR2_mips64el || BR2_powerpc || BR2_sh || BR2_sh64 || BR2_i386 || BR2_x86_64
> -	depends on !BR2_TOOLCHAIN_HAS_THREADS || !(BR2_UCLIBC_VERSION_SNAPSHOT || BR2_TOOLCHAIN_USES_GLIBC)
> +comment "libunwind needs a toolchain w/ threads"
> +	depends on BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS
> +	depends on !BR2_TOOLCHAIN_HAS_THREADS
>
Thomas Petazzoni Jan. 25, 2016, 10:20 p.m. UTC | #2 
Romain,

On Mon, 25 Jan 2016 22:59:40 +0100, Romain Naour wrote:

> > diff --git a/package/libunwind/Config.in b/package/libunwind/Config.in
> > index 85cb472..6f747ae 100644
> > --- a/package/libunwind/Config.in
> > +++ b/package/libunwind/Config.in
> > @@ -1,15 +1,32 @@
> > +# libunwind is only available for a certain subset of the
> > +# architectures (as visible in the list of architectures supported
> > +# with the glibc C library below).
> > +#
> > +# In addition to this, on some architectures libunwind requires the
> > +# *context() function from the C library, which are only available on
> > +# certain architectures in uClibc, and not available at all on
> > +# musl. But on some other architectures, libunwind works without using
> > +# the *context() functions, which allows it to be built with musl.
> > +config BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS
> > +	bool
> > +	default y if BR2_TOOLCHAIN_USES_GLIBC && \
> > +		(BR2_arm || BR2_armeb || BR2_mips || BR2_mipsel || BR2_mips64 || \
> > +		 BR2_mips64el || BR2_powerpc || BR2_sh || BR2_sh64 || BR2_i386 || BR2_x86_64)
> > +	default y if BR2_TOOLCHAIN_USES_UCLIBC && \
> > +		(BR2_arm || BR2_armeb || BR2_i386 || BR2_mips || BR2_mipsel || \
> > +		 BR2_x86_64)
> > +	default y if BR2_TOOLCHAIN_USES_MUSL && \
> > +		(BR2_arm || BR2_armeb || BR2_i386 || BR2_x86_64)
> > +
> >  config BR2_PACKAGE_LIBUNWIND
> >  	bool "libunwind"
> >  	depends on BR2_TOOLCHAIN_HAS_THREADS
> > -	depends on (BR2_UCLIBC_VERSION_SNAPSHOT || BR2_TOOLCHAIN_USES_GLIBC) # {g,s}etcontext
> > -	depends on BR2_arm || BR2_armeb || BR2_mips || BR2_mipsel || BR2_mips64 || \
> > -		BR2_mips64el || BR2_powerpc || BR2_sh || BR2_sh64 || BR2_i386 || BR2_x86_64
> > +	depends on BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS

Thanks for reviewing!

> Build tested on musl and x86_64.
> Checked that libunwind doesn't build with uClibc-snapshot and uClibc-ng.

I don't get this sentence however. libunwind should build with
uClibc-ng on the architectures listed in
BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS, no?

Thanks,

Thomas
Romain Naour Jan. 25, 2016, 10:33 p.m. UTC | #3 
Thomas,

Le 25/01/2016 23:20, Thomas Petazzoni a écrit :
> Romain,
> 
> On Mon, 25 Jan 2016 22:59:40 +0100, Romain Naour wrote:
> 
>>> diff --git a/package/libunwind/Config.in b/package/libunwind/Config.in
>>> index 85cb472..6f747ae 100644
>>> --- a/package/libunwind/Config.in
>>> +++ b/package/libunwind/Config.in
>>> @@ -1,15 +1,32 @@
>>> +# libunwind is only available for a certain subset of the
>>> +# architectures (as visible in the list of architectures supported
>>> +# with the glibc C library below).
>>> +#
>>> +# In addition to this, on some architectures libunwind requires the
>>> +# *context() function from the C library, which are only available on
>>> +# certain architectures in uClibc, and not available at all on
>>> +# musl. But on some other architectures, libunwind works without using
>>> +# the *context() functions, which allows it to be built with musl.
>>> +config BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS
>>> +	bool
>>> +	default y if BR2_TOOLCHAIN_USES_GLIBC && \
>>> +		(BR2_arm || BR2_armeb || BR2_mips || BR2_mipsel || BR2_mips64 || \
>>> +		 BR2_mips64el || BR2_powerpc || BR2_sh || BR2_sh64 || BR2_i386 || BR2_x86_64)
>>> +	default y if BR2_TOOLCHAIN_USES_UCLIBC && \
>>> +		(BR2_arm || BR2_armeb || BR2_i386 || BR2_mips || BR2_mipsel || \
>>> +		 BR2_x86_64)
>>> +	default y if BR2_TOOLCHAIN_USES_MUSL && \
>>> +		(BR2_arm || BR2_armeb || BR2_i386 || BR2_x86_64)
>>> +
>>>  config BR2_PACKAGE_LIBUNWIND
>>>  	bool "libunwind"
>>>  	depends on BR2_TOOLCHAIN_HAS_THREADS
>>> -	depends on (BR2_UCLIBC_VERSION_SNAPSHOT || BR2_TOOLCHAIN_USES_GLIBC) # {g,s}etcontext
>>> -	depends on BR2_arm || BR2_armeb || BR2_mips || BR2_mipsel || BR2_mips64 || \
>>> -		BR2_mips64el || BR2_powerpc || BR2_sh || BR2_sh64 || BR2_i386 || BR2_x86_64
>>> +	depends on BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS
> 
> Thanks for reviewing!
> 
>> Build tested on musl and x86_64.
>> Checked that libunwind doesn't build with uClibc-snapshot and uClibc-ng.
> 
> I don't get this sentence however. libunwind should build with
> uClibc-ng on the architectures listed in
> BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS, no?

Ha, sorry (missing some context).
I build tested libunwind with uClibc-snapshot on powerpc with the master branch
to verify that it doesn't build.
Then, I switched to your series with a small modification to enable powerpc and
verify that doesn't build as for uClibc-snapshot on the same architecture.

The build error look like:
In file included from ../include/libunwind.h:15:0,
                 from ppc32/Lglobal.c:2:
../include/libunwind-ppc32.h:182:9: erreur: unknown type name ‘ucontext_t’
 typedef ucontext_t unw_tdep_context_t;

So your BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS setting is correct.

Best regards,
Romain

> 
> Thanks,
> 
> Thomas
>
Thomas Petazzoni Jan. 25, 2016, 10:43 p.m. UTC | #4 
Romain,

On Mon, 25 Jan 2016 23:33:02 +0100, Romain Naour wrote:

> > I don't get this sentence however. libunwind should build with
> > uClibc-ng on the architectures listed in
> > BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS, no?
> 
> Ha, sorry (missing some context).
> I build tested libunwind with uClibc-snapshot on powerpc with the master branch
> to verify that it doesn't build.
> Then, I switched to your series with a small modification to enable powerpc and
> verify that doesn't build as for uClibc-snapshot on the same architecture.
> 
> The build error look like:
> In file included from ../include/libunwind.h:15:0,
>                  from ppc32/Lglobal.c:2:
> ../include/libunwind-ppc32.h:182:9: erreur: unknown type name ‘ucontext_t’
>  typedef ucontext_t unw_tdep_context_t;
> 
> So your BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS setting is correct.

Ok, thanks, understood!

In fact my BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS setting for uClibc is
simply based on:

$ find . | grep setcontext
./libc/sysdeps/linux/i386/setcontext.S
./libc/sysdeps/linux/arm/setcontext.S
./libc/sysdeps/linux/x86_64/setcontext.S
./libc/sysdeps/linux/mips/setcontext.S

In the uclibc-ng sources. I've done some build testing of course, but
clearly not all the combinations of architectures / C libraries.

Best regards,

Thomas
diff mbox

Patch

diff --git a/package/libunwind/Config.in b/package/libunwind/Config.in
index 85cb472..6f747ae 100644
--- a/package/libunwind/Config.in
+++ b/package/libunwind/Config.in
@@ -1,15 +1,32 @@ 
+# libunwind is only available for a certain subset of the
+# architectures (as visible in the list of architectures supported
+# with the glibc C library below).
+#
+# In addition to this, on some architectures libunwind requires the
+# *context() function from the C library, which are only available on
+# certain architectures in uClibc, and not available at all on
+# musl. But on some other architectures, libunwind works without using
+# the *context() functions, which allows it to be built with musl.
+config BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS
+	bool
+	default y if BR2_TOOLCHAIN_USES_GLIBC && \
+		(BR2_arm || BR2_armeb || BR2_mips || BR2_mipsel || BR2_mips64 || \
+		 BR2_mips64el || BR2_powerpc || BR2_sh || BR2_sh64 || BR2_i386 || BR2_x86_64)
+	default y if BR2_TOOLCHAIN_USES_UCLIBC && \
+		(BR2_arm || BR2_armeb || BR2_i386 || BR2_mips || BR2_mipsel || \
+		 BR2_x86_64)
+	default y if BR2_TOOLCHAIN_USES_MUSL && \
+		(BR2_arm || BR2_armeb || BR2_i386 || BR2_x86_64)
+
 config BR2_PACKAGE_LIBUNWIND
 	bool "libunwind"
 	depends on BR2_TOOLCHAIN_HAS_THREADS
-	depends on (BR2_UCLIBC_VERSION_SNAPSHOT || BR2_TOOLCHAIN_USES_GLIBC) # {g,s}etcontext
-	depends on BR2_arm || BR2_armeb || BR2_mips || BR2_mipsel || BR2_mips64 || \
-		BR2_mips64el || BR2_powerpc || BR2_sh || BR2_sh64 || BR2_i386 || BR2_x86_64
+	depends on BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS
 	help
 	  C API to determine the call-chain of a program.
 
 	  http://www.nongnu.org/libunwind/index.html
 
-comment "libunwind needs a uclibc snapshot or (e)glibc toolchain w/ threads"
-	depends on BR2_arm || BR2_armeb || BR2_mips || BR2_mipsel || BR2_mips64 || \
-		BR2_mips64el || BR2_powerpc || BR2_sh || BR2_sh64 || BR2_i386 || BR2_x86_64
-	depends on !BR2_TOOLCHAIN_HAS_THREADS || !(BR2_UCLIBC_VERSION_SNAPSHOT || BR2_TOOLCHAIN_USES_GLIBC)
+comment "libunwind needs a toolchain w/ threads"
+	depends on BR2_PACKAGE_LIBUNWIND_ARCH_SUPPORTS
+	depends on !BR2_TOOLCHAIN_HAS_THREADS