parallel and recursive make

[Ethan Tira-Thompson]

I have what seems a relatively simple issue, but I can't figure out the solution.

I have a project, with a module built via recursive make.

This module has some header files which are constructed from a sort of template file (call it a 'fsm' file to avoid confusion with C++ templates or such)

Source files in the project then include the generated header files from the module.

The problem is that when using parallel builds, if a 'fsm' file is modified, the module headers are regenerated, but the project source files are only recompiled on the *next* make.  If I use a single-threaded build, then everything is kept in sync properly.

How can I fix this?  I've attached a very small sample of the issue.  Fails on make 3.81, on Fedora and OS X.

Thanks,

  -Ethan

Correct build (single process):

580 ~/maketest$ touch sub/bar.h.fsm && make

Processing makefile

make -C "sub"

cp "bar.h.fsm" "bar.h" && touch "bar.h"

echo "foo.d foo.o: sub/bar.h" > "foo.d"

Processing makefile

make -C "sub"

make[1]: Nothing to be done for `all'.

g++ "foo.cc" -o "foo.o" -c 

g++ "foo.o" -o "foo" -L/opt/local/lib

Bad build when parallel:

581 ~/maketest$ touch sub/bar.h.fsm && make -j2

Processing makefile

make -C "sub"

cp "bar.h.fsm" "bar.h" && touch "bar.h"

make: Nothing to be done for `all'.

Catches it the next time though:

582 ~/maketest$ make -j2

Processing makefile

make -C "sub"

make[1]: Nothing to be done for `all'.

echo "foo.d foo.o: sub/bar.h" > "foo.d"

Processing makefile

make -C "sub"

make[1]: Nothing to be done for `all'.

g++ "foo.cc" -o "foo.o" -c 

g++ "foo.o" -o "foo" -L/opt/local/lib

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