Coverage generation isn't working correctly on OSX with Homebrew gcc

[zackw]

On Travis, postprocessing of test coverage information is failing catastrophically when we try to use Homebrew gcc on OSX:

Scanning . for .gcda files ...
geninfo: WARNING: /Users/travis/build/besser82/libxcrypt/build/lib/.libs/libcrypt_la-alg-des.gcno: Overlong record at end of file!
Found 69 data files in .
Processing lib/.libs/libcrypt_la-alg-des.gcda
geninfo: WARNING: cannot find an entry for alg-des.c##18b2c852c0edeffadf6cc9e0c9c509e2.gcov in .gcno file, skipping file!
geninfo: WARNING: cannot find an entry for byteorder.h##ae93dab466d845fca9fc8a160120b720.gcov in .gcno file, skipping file!
geninfo: WARNING: /Users/travis/build/besser82/libxcrypt/build/lib/.libs/libcrypt_la-alg-gost3411-2012-core.gcno: Overlong record at end of file!
Processing lib/.libs/libcrypt_la-alg-gost3411-2012-core.gcda
geninfo: WARNING: cannot find an entry for alg-gost3411-2012-core.c##f731ebae2ff82159365370d58469ea11.gcov in .gcno file, skipping file!
geninfo: WARNING: /Users/travis/build/besser82/libxcrypt/build/lib/.libs/libcrypt_la-alg-gost3411-2012-hmac.gcno: Overlong record at end of file!

There's a set of these errors for every source file, and we get no usable coverage information to upload.

This is probably a case of the lcov toolset being out of sync with Homebrew gcc's gcov, and someone with direct access to an OSX build environment should find it pretty easy to fix, but I've reached the limit of my patience with debugging via logfiles only.

[zackw]

On slightly further investigation, this is linux-test-project/lcov#58 , which has been fixed in lcov trunk, but the fix has not yet appeared in an official release. Ubuntu cherry-picked the patch, so it works in the Travis Linux environment, but Homebrew didn't. I cannot figure out whether Homebrew "formulae" are capable of cherry-picking patches. I'm going to file an issue on the formula and close this issue; the problem will resolve itself whenever the Homebrew package of lcov picks up the fix (either via cherry-picking or via an official release).

[zackw]

Homebrew/homebrew-core#50043