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This is a really big step towards getting parallel make to work.
Note that this is not yet complete. There are still a few `details' to
fix before this works 100%. Specifically: sequential make (compat) and
parallel make don't use the same engine, and the parallel engine still
has a few limitations. For instance, some known issues:
- parallel make does not deal with .phony targets correctly all the time.
- some errors are deadly in parallel make mode.
- parallel make NEEDS way more sturdy correspondance of file system paths
and target names, since it often needs to match dependencies to targets
before the corresponding files exist.
- some local variables like $* get set in a bogus way in some cases.
- suffix handling has issues, especially related to the NULL suffix.
So, if you find stuff that does NOT yet work with parallel make, don't go
blindly try to fix the Makefile. It's very likely you might have stumbled
into a make bug. (unless you really, really, understand Makefiles, DON'T
GO CHANGING THEM YET).
Tested by lots of people, thanks go to miod@, and robert@ among other people.
Quick summary of what this does:
- remove `saving commands' extension (it's not really usable, nor used)
- move compat job runner and parallel interrupt handling into engine.c
- tweak the code so that both compat and parallel mode use the same job runner
and the same interrupt handling. Remove the other one.
- optimize job runner so that, in parallel mode, the last command does not
fork if we can avoid it (as it's already running in a sub shell).
- scrape all the code that dealt with creating shell scripts from commands.
- scrape all the code that dealt with recognizing special sequences in
command output to print/not print output.
- fix the parallel job pipe to not keep around file descriptors that are not
needed.
- replace the parallel job buffering with a nicer one, that deals with
non-blocking descriptors to try to agregate as much output from one job in
one go (greed) to unconfuse the users.
- create two pipes per job, so that stdout and stderr stay separate.
- make job token printing a debug option.
- always use the parallel job-runner to `execute' commands, even if we just
print them out.
- store list of errors encountered during parallel make running, and print them
on exit, so that we know what went wrong.
- add a dirty hack to targ.c to deal with paths produced by gccmakedep.
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