Building lldb-instr fails with undefined reference to symbol when building with BUILD_SHARED_LIBS=ON

[KyleFromKitware]

Building lldb-instr fails with the following error when I build with BUILD_SHARED_LIBS=ON:

: && /usr/bin/c++ -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wno-misleading-indentation -fdiagnostics-color -Wno-deprecated-declarations -Wno-unknown-pragmas -Wno-strict-aliasing -Wno-stringop-truncation -g -Wl,-rpath-link,<redacted>/./lib tools/lldb/tools/lldb-instr/CMakeFiles/lldb-instr.dir/Instrument.cpp.o -o bin/lldb-instr  -Wl,-rpath,"\$ORIGIN/../lib"  -lpthread  lib/libclangCodeGen.so.17git  lib/libclangTooling.so.17git  lib/libclangFrontend.so.17git  lib/libclangSerialization.so.17git  lib/libclangAST.so.17git  lib/libclangRewrite.so.17git  lib/libclangLex.so.17git  lib/libclangBasic.so.17git  -Wl,-rpath-link,<redacted>/lib && :
/usr/bin/ld: tools/lldb/tools/lldb-instr/CMakeFiles/lldb-instr.dir/Instrument.cpp.o: undefined reference to symbol '_ZNK4llvm15SmallVectorBaseIjE5emptyEv'
/usr/bin/ld: <redacted>/./lib/libLLVMSupport.so.17git: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status

I suspect lldb-instr is missing some library dependency.

[llvmbot]

@llvm/issue-subscribers-lldb

[KyleFromKitware]

The following patch seems to fix it:

diff --git a/lldb/tools/lldb-instr/CMakeLists.txt b/lldb/tools/lldb-instr/CMakeLists.txt
index a1bbd7e2b7c9..9e9a757c4329 100644
--- a/lldb/tools/lldb-instr/CMakeLists.txt
+++ b/lldb/tools/lldb-instr/CMakeLists.txt
@@ -12,3 +12,8 @@ add_lldb_tool(lldb-instr
     clangTooling
 
   )
+target_link_libraries(
+  lldb-instr
+  PRIVATE
+    LLVMSupport
+  )

Shall I submit this?

[JDevlieghere]

This is probably the result of e12a950. Let's make sure that if we undo that we don't break the Xcode build in the process.

[KyleFromKitware]

That looks like it is almost certainly the cause, considering what the fix looks like.

[KyleFromKitware]

I'm also investigating if the issue fixed by e12a950 might be a CMake bug, I'll report here when I know more.

[KyleFromKitware]

I just tried building on Xcode with the commit before e12a950 and it built fine, even with two references to libLLVMSupport.a. @jimingham could you please tell me how to reproduce the build that failed without e12a950?

[JDevlieghere]

I was able to reproduce the issue too. Here's what I did:

Perform a standalone build of LLVM+Clang:

$ cmake ../llvm-project/llvm \
    -G Ninja \
    -DCMAKE_BUILD_TYPE='RelWithDebInfo' \
    -DLLVM_ENABLE_ASSERTIONS:BOOL=ON \
    -DLLVM_ENABLE_PROJECTS='llvm;clang'
$ ninja

Perform a standalone build of LLDB:

$ cmake ../llvm-project/lldb  \
    -C../llvm-project/lldb/cmake/caches/Apple-lldb-Xcode.cmake \
    -DLLVM_DIR=<absolute path to standalone llvm build>/lib/cmake/llvm \
    -DClang_DIR=<absolute path to standalone llvm build>/lib/cmake/clang
$ cmake --build .

[KyleFromKitware]

@JDevlieghere What version of Xcode are you using? I just tried this with Xcode 12.2 and it built fine.