I suspect this is because these are C or Fortran sub-projects. I'm looking for some clean way to tell Cmake to apply externis to all the C++ only subprojects if possible. I'll see what I can come up with.
I'd also like to know, if multiple GCC commands end up pointing to the same trace.json, especially in a parallel build, will externis automagically ensure that it doesn't step over itself?
I figured out a way to set it at a top level, so it only happens with C++ files:
target_compile_options(${NAME} PUBLIC
$<$<COMPILE_LANGUAGE:CXX>:-fplugin=externis -fplugin-arg-externis-trace-dir=(where I want to put traces)>
)
But as I suspected, it is not a single trace file. It's thousands of trace files. Is there some way to collate all the data into one larger picture of how the build progressed?