Bug#836806: clang on dual arch (x86_64/i386) system tries to use 64 bit libs when m32 is passed

[Matt Parnell]

Package: clang (all versions?)

Ever since the upgrade to gcc6/libstdc++6, this has been an issue.
I build a private application that only works with 32 bit libs currently and
as a result have to include the i386 architecture to pull in a few
specific libraries.
For whatever reason, clang chooses to ignore -m32 and use the x86_64 libraries
if I do not disable (rename/move) them.

Before workaround:

clang -v -m32
Debian clang version 3.6.2-3 (tags/RELEASE_362/final) (based on LLVM 3.6.2)
Target: i386-pc-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/5.4.1
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/6.1.1
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.1
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.1.1
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.4.1
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/6.1.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.1.1
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.1.1
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

After:

clang -v -m32
Debian clang version 3.6.2-3 (tags/RELEASE_362/final) (based on LLVM 3.6.2)
Target: i386-pc-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/5.4.1
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/6.1.1
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.1
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.4.1
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/6.1.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.1
Selected GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/5.4.1
Candidate multilib: .;@m32
Selected multilib: .;@m32
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