I'm trying to write bazel rules for a 3rd party library that specify different pre-processor define values per file i.e.
c++ ... -DVALUE=file1.cpp -c file1.cpp
c++ ... -DVALUE=file2.cpp -c file2.cpp
c++ ... -DVALUE=file3.cpp -c file3.cpp
This is basically set_property() on the file to add COMPILE_DEFINITIONS in CMake.
Using copts or local_defines for cc_library() doesn't seem to support this use case as they are common for all source files in the library.
The terrible ways to do this that I can think of:
-include to add the definition.Is there a better way to achieve this? Thanks!
The simplest approach to that is to just make a separate cc_library for each file, and then aggregate them together. Bazel isn't actually going to create a separate .a file in most configurations, so it doesn't change very much. A macro or list comprehension may be helpful to avoid copy/paste for the attribute values shared between all of the cc_libary targets.
The other option is writing a custom rule. my_c_compile and my_c_archive are some basic examples, you could combine them pretty easily into a single rule that takes multiple source files and applies separate user_compile_flags to each. That seems like a lot of work though.
Bazel also includes a full implementation of cc_library in Starlark which you could start from when writing a custom rule, but that's really complicated in many ways which you don't need. It's in src/main/starlark/builtins_bzl/common/cc/cc_library.bzl.