Hi,
I'm hoping for an explanation for some strange behavior that I see
when attempting a parallel build. Its
not the classic race condition, but rather something wrong with my
pattern rule. Hopefully this will
be an obvious problem with a nice solution.
My pattern rule reads like this:
lf/% af/% nf/% pf/%:
do_stuff()
My intent is to invoke the same function for any make target with one of
the 4 subdirs listed above.
There are dependencies between them. e.g., lf/abc depends on af/abc and
nf/aaa. af/abc
depends on pf/ppp while nf/aaa depends on pf/p1... Thus there are
opportunities for parallel.
But the "notdir" part of the targets DO repeat in af and lf.
This works fine with -j 1 builds - everything builds in order as
needed. However, I run into a
problem with -j 2. I think there is a problem when I have lf/abc
dependent on af/abc using the
pattern rule above. make builds af/abc in parallel with nf/aaa. af/abc
finishes, and then nf/aaa
finishes and make thinks its done! It never attempts to build lf/abc
... again only with multiple jobs.
Here's the last bit of make's -d output - after af/abc finishes.
Reaping winning child 0x09b975f8 PID 27863
Removing child 0x09b975f8 PID 27863 from chain.
Released token for child 0x09b975f8 (af/abc).
Live child 0x09b968e8 (nf/aaa) PID 22912
Considering target file `lf/abc'.
File `lf/abc' was considered already.
Live child 0x09b968e8 (nf/aaa) PID 22912
Thanks for reading.
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