Build failure on multithreaded build.

[jstressman]

Sometimes works, sometimes doesn't.

hrev53701

Ryzen 9 3950x CPU with Ubuntu 19.10 64bit.

Using command

jam -q -j32 @nightly-anyboot

Failed with -j30 as well.

[jstressman]

-j32 build fail of hrev53701

[pulkomandy]

Build error: header files for libpng, libjpeg, etc are not found.

Suspicious things found in the logs:

• I see two invocations of ExtractHpkgArchive1 for libpng (lines 4530 and 4547), is this expected?
• Compilation of the PNG translator starts after that (line 16025) and eventually fails (line 31138)

So, I suspect one of these two:

• The double extraction of the package is creating an invalid result
• Or, the build of the PNG translator is completed before extraction is complete

The latter is quite plausible, due to the way we manage these extraction rules. Basically, as soon as the rule has created the libpng directory in build_packages, the PNG translator assumes that the dependency is satisfied. It does not depend on specific files inside that directory.

Workaround: once you have a succesful build, these packages are extracted only on updates which happen rarely. So the following builds will be fine.