Intermittent build failure with multi-job builds (make -j)

[tobiasb-ms]

Following instructions here: in the README, I got the latest released tarball, configured with:

./configure --with-examples --with-drill

And built with make.

When I build with make or make -j1 (so a single job), it builds fine.

If I build with multiple threads like with make -j32, I get intermittent errors like:

./libtool --tag=CC --quiet --mode=link gcc -DOPENSSL_API_COMPAT=10100 -fno-strict-aliasing -Wunused-function -Wstrict-prototypes -Wwrite-strings -W -Wall -g -O2 -D_GNU_SOURCE   examples/ldns-verify-zone.lo compat/b64_pton.lo compat/b64_ntop.lo libldns.la -lssl  -lcrypto  -o examples/ldns-verify-zone ./libldns.la
/usr/bin/ld: examples/.libs/ldns-testns.o: in function `main':
/home/tobiasb/scratch/ldns-cool/ldns-1.8.4/./examples/ldns-testns.c:599:(.text.startup+0x3e4): undefined reference to `perr�'
collect2: error: ld returned 1 exit status
make: *** [Makefile:210: examples/ldns-testns] Error 1

(NOTE that the non-printable character was part of the error output itself.)

I've reproed this on Ubuntu 24.04 and on Azure Linux 3.

Obviously, this is easy to work around but it if this is a known issue, I haven't been able to find it. May be worth documenting it explicitly, or working out the makefile magic to fix it.

[wcawijngaards]

After some searching in the Makefile, and then trying to build but that does not replicate it here. It does have other failure-related output that does not stop the compilation. But then I spotted that it tries to build both .lo and .o files at the same time. Since the .lo then writes to the .o as well, that overwrites the same file and in the multi-job builds then the partially overwritten file can both enable another job to start because of the previous written contents, but then fail when the newly written contents is not completed, even though the contents are likely mostly identical, apart from compiler build randomness during optimization and stuff like that. This is in particular for the example programs.

[wcawijngaards]

Thank you for the report, the fix improves the build so that it does not have overwrites, and that likely fixes some issues during a multi-job build. That should improve the build situation!

[tobiasb-ms]

Wow, thanks for the fast turnaround. I applied the patch and built 30 times with no failures -- nice work!