gcc 12: language Makefile fragment and generated files

[Simon Richter <Simon.Richter@hogyros.de>]

Hi,

I see build failures of the Debian gcc 12 packages on machines with a 
lot of threads[1]. This package adds in Modula-2 support before 
building, and the M2 fragment uses $(generated_files) as a dependency 
for the language specific options.

Because $(generated_files) is set after including the fragments, that 
doesn't really work, so the dependency is missing, and the M2 frontend 
is built before insn-attr-common.h is available.

I'm not sure how to address this best.

My initial approach was be to define "M2_OBJS", which I figured would be 
the name that the fragment processing would consult for the list of 
extra objects built from gcc/m2/Make-lang.in, and set up proper 
dependency tracking for these and include them in the order-only 
dependency at the end of gcc/Makefile.in. That didn't work, though.

My two immediate questions:

  - how is a language supposed to depend on the target header (it's 
i386.h that pulls in insn-attr-common.h)?
  - did I understand the purpose of the _OBJS processing correctly?

    Simon

[1] https://bugs.debian.org/1053551