[Boost-build] Issue running bjam with multiple jobs and custom code generator

Subject: [Boost-build] Issue running bjam with multiple jobs and custom code generator
From: Christophe B. (boost_at_[hidden])
Date: 2016-11-04 12:27:58

Hi,

I developed a protoc.jam (see attachment) allowing to invoke an external 
code generator tool (protoc from protobuf library). The tool generates 
c++ unit files X.pb.h X.pb.cc from a source X.proto.

When I run bjam -j1 from scratch everything works like a charm.

When I run bjam -j6 from scratch, I get compilation issues complaining 
that the generated X.pb.h file is missing, because the compiler compiles 
other cpp units in parallel before protoc has fully finished.

Why it does work correctly with one job and not with multiple jobs 
remains a mystery to me. I would expect that bjam detects the 
dependencies of cpp units with the generated X.pb.h file and waits for 
its generation before starting compilation of depending cpp units.

I also attached the Jamfile of my project.

Any help would be appreciated.

Christophe B.