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Date: Sat, 28 Jun 2014 12:53:08 +0200
From: Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
To: musl@...ts.openwall.com
Subject: Issues with the 1.1.2 pre-built musl toolchains
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@...te:~/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@...te:~/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@...te:~/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@...te:~/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@...te:~/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@...te:~/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
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