Semi-colon separated lists in portfile becomes multi-quote guarded, space delimited strings on the command line

[MathiasMagnus]

I'm trying to enhance the LLVM package to suit my needs, but there is a big problem which I spent over a day now trying to come over. (This is the kind of aggravation which makes me start to think that Vcpkg does not scale.)

LLVM requires a LLVM_TARGETS_TO_BUILD variable which by the docs should be a semi-colon delimited string, so the native CMake encoding for lists. Currently the LLVM port only builds the X86 target, but I want it to also build GPU-related targets. (Currently it's hardcoded, but before I submit, I'll make non-x86 targets features of the package.) Problem is, that if I write this in the portfile:

vcpkg_configure_cmake(
    SOURCE_PATH ${SOURCE_PATH}
    PREFER_NINJA
    OPTIONS
        -DLLVM_TARGETS_TO_BUILD="X86;AMDGPU;NVPTX"
        -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD="X86;AMDGPU;NVPTX"
        -DLLVM_INCLUDE_TOOLS=ON
        -DLLVM_INCLUDE_UTILS=OFF
        -DLLVM_INCLUDE_EXAMPLES=OFF
        -DLLVM_INCLUDE_TESTS=OFF
        -DLLVM_ABI_BREAKING_CHECKS=FORCE_OFF
        -DLLVM_TOOLS_INSTALL_DIR=tools/llvm
        -DLLVM_PARALLEL_LINK_JOBS=8
)

It does not matter if I use quotes or not, the command-line invocation contains:

"-DLLVM_TARGETS_TO_BUILD="X86" "AMDGPU" "NVPTX""

Things from here on start to fall apart spectacularly. (LLVM_EXPERIMENTAL_TARGETS_TO_BUILD is undocumented, which targets should be placed there, it just argues seemingly randomly if something's not there. So I just duplicate everything. The two get merged anyway in the main CMakeLists.txt file via)

set(LLVM_TARGETS_TO_BUILD
   ${LLVM_TARGETS_TO_BUILD}
   ${LLVM_EXPERIMENTAL_TARGETS_TO_BUILD})
list(REMOVE_DUPLICATES LLVM_TARGETS_TO_BUILD)

This is the code snippet that calls the LLVM-build Python scripts:

message(STATUS "Constructing LLVMBuild project information")
execute_process(
  COMMAND ${PYTHON_EXECUTABLE} -B ${LLVMBUILDTOOL}
            ...
            --enable-targets "${LLVM_TARGETS_TO_BUILD}"
            ...
  RESULT_VARIABLE LLVMBUILDRESULT)

The error becomes:

-- LLVMHello ignored -- Loadable modules not supported on this platform.
-- Targeting X86 AMDGPU NVPTX
CMake Error at lib/Target/CMakeLists.txt:18 (add_subdirectory):
  add_subdirectory given source "X86 AMDGPU NVPTX" which is not an existing
  directory.


CMake Error at cmake/modules/LLVM-Config.cmake:175 (message):
  Target X86 AMDGPU NVPTX is not in the set of libraries.
Call Stack (most recent call first):

of course, because the scripts got derailed a few lines back in LLVM-Config.cmake before invoking the Python scripts when it tried

list(FIND LLVM_TARGETS_TO_BUILD "${LLVM_NATIVE_ARCH}" have_native_backend)

The variable with the semi-colons stripped is no longer a list.

The fix is to add:

message(STATUS "Constructing LLVMBuild project information")
message(STATUS "LLVM_TARGETS_TO_BUILD: ${LLVM_TARGETS_TO_BUILD}")
string(REPLACE " " ";" LLVM_TARGETS_TO_BUILD ${LLVM_TARGETS_TO_BUILD})
message(STATUS "LLVM_TARGETS_TO_BUILD: ${LLVM_TARGETS_TO_BUILD}")

which results in configuration succeeding.

-- Constructing LLVMBuild project information
-- LLVM_TARGETS_TO_BUILD: X86 AMDGPU NVPTX
-- LLVM_TARGETS_TO_BUILD: X86;AMDGPU;NVPTX
-- LLVMHello ignored -- Loadable modules not supported on this platform.
-- Targeting X86
-- Targeting AMDGPU
-- Targeting NVPTX

Summa summarum

Having to patch the build scripts solely because Vcpkg messes up command-line invocations containing native CMake lists is not okay.