[C++] CMake error when Arrow is built as subproject: ARROW_SIMD_LEVEL undefined in io/CMakeLists.txt

[zanmato1984]

Describe the enhancement requested

Summary

When Arrow is added as a subproject (FetchContent + SOURCE_SUBDIR cpp), CMake configuration fails in
cpp/src/arrow/io/CMakeLists.txt:48. The if() uses ${ARROW_SIMD_LEVEL} and crashes if the
variable is undefined, which happens because ARROW_DEFINE_OPTIONS defaults to OFF for subprojects.

Repro

Minimal CMakeLists.txt:

cmake_minimum_required(VERSION 3.20)
project(bundled-arrow-example LANGUAGES CXX)
include(FetchContent)

set(ARROW_BUILD_SHARED OFF CACHE BOOL "" FORCE)
set(ARROW_BUILD_STATIC ON CACHE BOOL "" FORCE)
set(ARROW_BUILD_TESTS OFF CACHE BOOL "" FORCE)
set(ARROW_BUILD_UTILITIES OFF CACHE BOOL "" FORCE)
set(ARROW_COMPUTE OFF CACHE BOOL "" FORCE)
set(ARROW_ACERO OFF CACHE BOOL "" FORCE)
set(ARROW_DATASET OFF CACHE BOOL "" FORCE)
set(ARROW_IPC OFF CACHE BOOL "" FORCE)
set(ARROW_PARQUET OFF CACHE BOOL "" FORCE)

set(ARROW_VERSION "23.0.0")
FetchContent_Declare(
  arrow
  URL https://github.com/apache/arrow/archive/refs/tags/apache-arrow-${ARROW_VERSION}.tar.gz
  SOURCE_SUBDIR cpp
)
FetchContent_MakeAvailable(arrow)

Configure:

cmake -S . -B build

CMake fails with:

CMake Error at build/_deps/arrow-src/cpp/src/arrow/io/CMakeLists.txt:48 (if):
  if given arguments:
    "NOT" "(" "STREQUAL" "NONE" ")" "AND" "NOT" "(" "STREQUAL" "NEON" ")"
  Unknown arguments specified

Component(s)

C++

[kou]

Issue resolved by pull request 49165
#49165