CODEWITHSUNDEEP
makefilegnu-parallel
Euklides
Euklides

Reputation: 584

Can GNU make create broken binaries when building in parallel?

I am working in a project where we have just added parallelism to our build system, using GNU Make.

We build both libraries and the programs in parallel.

First we build all the libs necessary for the binaries. After the libs are created we start building the binaries.

Now when running our programs we have found that one of the binaries dont run as expected. Is it possible that GNU Make could cause broken binaries when building in parallel but still link correctly? If that is the case, what is the common cause and how can one avoid it?

Upvotes: 0

Views: 112

Answers (1)

MadScientist
MadScientist

Reputation: 100856

Correct parallel builds depend on a correct makefile. If a build works serially but not in parallel, that means that your makefile has not declared all the prerequisites that it needs, so make doesn't realize it can't build target X until after target Y is complete.

However, it's extremely unlikely that these kinds of errors would allow the build to succeed: that is, the compiler or linker will almost always fail if things are building in the wrong order. It's hard for me to imagine how the build would succeed except by the purest chance, if at all (maybe if your tools overwrite an existing file instead of deleting it and writing it from scratch). Of course you given no information about exactly what "don't run as expected" means so it's hard to say for sure.

To investigate you need to do some testing: does it fail the same way every time you do a parallel build? Does it fail even if you use different amounts of parallelism (different -j levels)? Does it continue to fail if you switch back to non-parallel builds? Does the build succeed with -j even if you start with a completely clean workspace (nothing built)?

Upvotes: 3

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