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Date: Thu, 21 Jan 2016 21:06:26 +0100
From: Szabolcs Nagy <nsz@...t70.net>
To: N Jain <jain61@...il.com>
Cc: musl@...ts.openwall.com
Subject: Re: MUSL issue while loading C++ lib
* N Jain <jain61@...il.com> [2016-01-21 14:05:41 -0500]:
>
> Also searching online I saw some issues with versions for
> GLIBCXX but don't know how to confirm if this is not the problem with MUSL
> toolchain I generated.
>
symbol versioning can cause problems, but gcc-5
libstdc++ and libgcc_s should work
> > > echo 'int main(){}' |g++ -xc++ -
> >
>
> I am not sure where to issue this command ?
i meant you should create a minimal dynamic linked
binary with your toolchain and analyze that
> > > readelf -ld ./a.out
> >
>
> INTERP 0x000114 0x00010114 0x00010114 0x00016 0x00016 R 0x1
> [Requesting program interpreter: /lib/ld-musl-arm.so.1]
...
> Dynamic section at offset 0xc24 contains 26 entries:
> Tag Type Name/Value
> 0x00000001 (NEEDED) Shared library: [libstdc++.so.6]
> 0x00000001 (NEEDED) Shared library: [libgcc_s.so.1]
> 0x00000001 (NEEDED) Shared library: [libc.so]
ok
> > > strace /lib/ld-musl-*.so.1 ./a.out
> >
>
> I don't have strace capability in my toolchain.
>
i wanted to see what paths are opened by the musl linker
to make sure the right libgcc_s.so.1 is found
> > > readelf -d /lib/libstdc++.so.6
> >
> 0x00000001 (NEEDED) Shared library: [libc.so]
> 0x00000001 (NEEDED) Shared library: [libgcc_s.so.1]
> 0x0000000e (SONAME) Library soname: [libstdc++.so.6]
ok
> > > readelf -aW /lib/libstdc++.so.6 |grep Unwind
> >
> 00137330 00051c16 R_ARM_JUMP_SLOT 00000000
> _Unwind_Resume_or_Rethrow
> 00137510 00083616 R_ARM_JUMP_SLOT 00000000
> _Unwind_GetLanguageSpecificData
my readelf prints the @GCC_3.x version suffix here.
i'm not sure what's the difference
> 1308: 00000000 0 FUNC GLOBAL DEFAULT UND
> _Unwind_Resume_or_Rethrow@..._3.3 (37)
> 2102: 00000000 0 FUNC GLOBAL DEFAULT UND
> _Unwind_GetLanguageSpecificData@..._3.0 (36)
...
> 14022: 00000000 0 FUNC GLOBAL DEFAULT UND
> _Unwind_Resume_or_Rethrow@@GCC_3.3
> 14816: 00000000 0 FUNC GLOBAL DEFAULT UND
> _Unwind_GetLanguageSpecificData@@GCC_3.0
ok
> > > readelf -aW /lib/libgcc_s.so.1 |grep Unwin
> >
>
> 302: 0001b350 28 FUNC GLOBAL DEFAULT 10
> _Unwind_GetLanguageSpecificData@@GCC_3.0
> 620: 0001ae04 36 FUNC GLOBAL DEFAULT 10
> _Unwind_Resume_or_Rethrow@@GCC_3.3
ok (.dynsym has the symbols)
> 1917: 0001b350 28 FUNC GLOBAL DEFAULT 10
> _Unwind_GetLanguageSpecificData
> 2235: 0001ae04 36 FUNC GLOBAL DEFAULT 10 _Unwind_Resume_or_Rethrow
this looks ok too
i think the musl linker should be able to deal with this :P
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