Compile options not being applied to modules

Development
1

I believe that I have encountered a bug in CMake. I am using C++ modules, and target_compile_options or compile_options are only being applied to the regular C++ files, not the module files (as observed through the compile_commands.json).

Interestingly enough, the options set through add_compile_definitions were applied to both file types.

I started debugging the issue and noticed divergence at target->GetCompileOptions(config, lang) The config and lang were the same, but the target objects were different. This is not what I expected both types of sources were connected to the same “target” as per CMake.

I don’t think this problem is exclusive to Ninja, but I am using Ninja, which is why I have filed this as such.

I am happy to provide a minimal error case, but I don’t see a good way to do that with this text-based interface. Maybe I could provide a zip or tar.gz of the files I have?

If you will forgive the style errors, this is the most important part:

cmake_minimum_required(VERSION 3.28)

add_library(test)

# Add module interface files
target_sources(test
  PUBLIC
    FILE_SET CXX_MODULES FILES
      ternary.cxx
)
# Add other source files
target_sources(test
  PUBLIC
    trie.cpp
)

string(TIMESTAMP TODAY "%Y-%m-%d")
message(STATUS "Current build date: ${TODAY}")

add_compile_definitions("UNIVERSAL")
add_compile_options("-DDATE_OPTION=${TODAY}")

add_executable(testo main.cpp)
set_target_properties(testo PROPERTIES OUTPUT_NAME "modules-test")
target_compile_options(testo PUBLIC "-DDATE_TARGET=${TODAY}")
target_compile_options(testo PUBLIC "$<$<CONFIG:DEBUG>:-Wall>")
target_link_libraries(testo test)
install(TARGETS testo)

“UNIVERSAL” is defined for all files as expected. However, -DDATE_OPTION, -DDATE_TARGET, and -Wall are only specified for main.cpp and trie.cpp. They are not provided for ternary.cxx as expected.