Issues with the 1.1.2 pre-built musl toolchains

Issues with the 1.1.2 pre-built musl toolchains

[Thomas Petazzoni]

Hello,

In Buildroot, we do have support for the pre-built musl toolchains
available from http://musl.codu.org/. Up until the musl 1.1.1
toolchains, everything was working fine, but unfortunately the musl
1.1.2 toolchains are no longer working correctly, for two reasons:

 * The first reason is that the sysroot support has been disabled,
   while this sysroot support was initially requested by us to be able
   to use those pre-built toolchains in Buildroot. Buildroot simply
   cannot support non-sysroot capable pre-built toolchains. Moreover,
   the commit that indicates why sysroot support is not desirable
   (https://bitbucket.org/GregorR/musl-cross/commits/16ccdedb5fae1fbf72fe61ceec35025e3b6a1557)
   indicates that it's related to a path issue in the libstdc++.la
   file, but I fail to see any difference between the libstdc++.la file
   of the 1.1.1 musl toolchains (which do have sysroot support), and
   the libstdc++.la file of the 1.1.2 musl toolchains (which no longer
   have sysroot support) :

 === musl 1.1.1 toolchains ===

thomas@skate:~/dl/arm-linux-musleabi-1.1.1$ ./bin/arm-musl-linuxeabi-gcc -v
[...]
Configured with: ../configure --prefix=/opt/cross/musl/arm-linux-musleabi --target=arm-linux-musleabi --with-sysroot=/opt/cross/musl/arm-linux-musleabi/arm-linux-musleabi --enable-languages=c,c++ --disable-libmudflap --disable-libsanitizer --disable-multilib --disable-lto-plugin --with-arch=armv4t
[...]
thomas@skate:~/dl/arm-linux-musleabi-1.1.1$ cat arm-linux-musleabi/lib/libstdc++.la
# libstdc++.la - a libtool library file
# Generated by libtool (GNU libtool 1.3134 2009-11-29) 2.2.7a
#
# Please DO NOT delete this file!
# It is necessary for linking the library.

# The name that we can dlopen(3).
dlname='libstdc++.so.6'

# Names of this library.
library_names='libstdc++.so.6.0.19 libstdc++.so.6 libstdc++.so'

# The name of the static archive.
old_library='libstdc++.a'

# Linker flags that can not go in dependency_libs.
inherited_linker_flags=''

# Libraries that this one depends upon.
dependency_libs=' -lm'

# Names of additional weak libraries provided by this library
weak_library_names=''

# Version information for libstdc++.
current=6
age=0
revision=19

# Is this an already installed library?
installed=yes

# Should we warn about portability when linking against -modules?
shouldnotlink=no

# Files to dlopen/dlpreopen
dlopen=''
dlpreopen=''

# Directory that this library needs to be installed in:
libdir='/opt/cross/musl/arm-linux-musleabi/arm-linux-musleabi/lib'

 === musl 1.1.2 toolchains ===

thomas@skate:~/dl/arm-linux-musleabi-1.1.2$ ./bin/arm-linux-musleabi-gcc -v
[...]
Configured with: ../configure --prefix=/opt/cross/musl/arm-linux-musleabi --target=arm-linux-musleabi --enable-languages=c,c++ --disable-libmudflap --disable-libsanitizer --disable-nls --disable-multilib --disable-lto-plugin --with-arch=armv4t
[...]
thomas@skate:~/dl/arm-linux-musleabi-1.1.2$ cat arm-linux-musleabi/lib/libstdc++.la
# libstdc++.la - a libtool library file
# Generated by libtool (GNU libtool 1.3134 2009-11-29) 2.2.7a
#
# Please DO NOT delete this file!
# It is necessary for linking the library.

# The name that we can dlopen(3).
dlname='libstdc++.so.6'

# Names of this library.
library_names='libstdc++.so.6.0.19 libstdc++.so.6 libstdc++.so'

# The name of the static archive.
old_library='libstdc++.a'

# Linker flags that can not go in dependency_libs.
inherited_linker_flags=''

# Libraries that this one depends upon.
dependency_libs=' -lm'

# Names of additional weak libraries provided by this library
weak_library_names=''

# Version information for libstdc++.
current=6
age=0
revision=19

# Is this an already installed library?
installed=yes

# Should we warn about portability when linking against -modules?
shouldnotlink=no

# Files to dlopen/dlpreopen
dlopen=''
dlpreopen=''

# Directory that this library needs to be installed in:
libdir='/opt/cross/musl/arm-linux-musleabi/arm-linux-musleabi/lib'

   As you can see, the libdir is identical in both .la files, so
   disabling the sysroot support hasn't changed anything, so I believe
   some incorrect assumption was made in commit
   https://bitbucket.org/GregorR/musl-cross/commits/16ccdedb5fae1fbf72fe61ceec35025e3b6a1557.

 * The second problem is that the kernel headers seem to no longer be
   present in the toolchains. I've seen that musl-cross has switched to
   using the sanitized kernel headers from Sabotage but the end result
   is that there are no longer any headers in usr/include/linux. For
   example, Buildroot looks at <linux/version.h> to see the kernel
   version of the headers, and uses that to ensure the user doesn't use
   kernel headers that are too old to build certain
   applications/libraries that need recent kernel headers. The
   disappearance of <linux/version.h> is problematic for this specific
   usage, but I believe the disappearance of *all* <linux/foo.h>
   headers is probably going to cause build issues as well. See:

thomas@skate:~/dl/arm-linux-musleabi-1.1.1$ LANG=C cat arm-linux-musleabi/usr/include/linux/version.h 
#define LINUX_VERSION_CODE 199686
#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))
thomas@skate:~/dl/arm-linux-musleabi-1.1.2$ LANG=C cat arm-linux-musleabi/usr/include/linux/version.h 
cat: arm-linux-musleabi/usr/include/linux/version.h: No such file or directory

Would it be possible to revert back to the build process of the 1.1.1
musl toolchains, which were working perfectly fine?

Thanks a lot,

Thomas Petazzoni
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

Re: Issues with the 1.1.2 pre-built musl toolchains

[Luca Barbato]

On 28/06/14 12:53, Thomas Petazzoni wrote:

If the problem is the .la file, what about removing it?

.la files cause more problems than what they supposedly solve (linking
deps for .a files, superceeded by pkgconf almost completely).

lu