Dynamic linking: undefined references when linking libLTO.so

[Quuxplusone]

Bugzilla Link	PR37591
Status	NEW
Importance	P normal
Reported by	Brian Vandenberg (phantall@gmail.com)
Reported on	2018-05-25 13:43:25 -0700
Last modified on	2018-05-25 13:48:44 -0700
Version	6.0
Hardware	Sun Solaris
CC	llvm-bugs@lists.llvm.org
Fixed by commit(s)
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I'm building on Solaris 10 / sparcv9, though I suspect this isn't solaris or
sparc specific.

I built with the following:

    cmake ../src/llvm \
    -DCMAKE_C_COMPILER=gcc-7.2.0 \
    -DCMAKE_CXX_COMPILER=g++-7.2.0 \
    -DGCC_INSTALL_PREFIX=$(dirname $(dirname $(which gcc-7.2.0))) \
    -DBUILD_SHARED_LIBS=ON \
    -DLINK_LLVM_DYLIB=ON \
    -DCMAKE_BUILD_TYPE=RelWithDebInfo

    make -j32

I'll explain why I built using those options in a separate comment.

When linking libLTO.so it fails with undefined references to the following:

    LLVMDisasmDispose
    LLVMCreateDisasmCPU
    LLVMCreateDisasm
    LLVMDisasmInstruction
    LLVMSetDisasmOptions

If I remove those entries from tools/lto/lto.exports then it links fine.

[Quuxplusone]

I built with

    BUILD_SHARED_LIBS=ON
    LINK_LLVM_DYLIB=ON

... because there are issues with global object initialization on
sparc/solaris.  Without those options clang-tblgen and llvm-tbglen both crash
while executing global constructors for command-line argument parsing.