No coverage with "--skip-solibs"

[pfrenzel]

I'm using kcov for C++ coverage reports.

After upgrading to Ubuntu 20.04 from 16.04 and recompiling of kcov I get zero coverage with the "--skip-solibs" flag.
I verified this with a "hello-world" program. Without this flag everything is fine but adding the flag I get zero coverage.

I also get this behavior with the ubuntu docker containers. There I used the default kcov-deb package.
Ubuntu 16.04 works but 20.04 does not. Here are my steps to reproduce. "hello" is just a hello-world.
docker run --rm -it --security-opt seccomp=unconfined -v $(pwd):/source ubuntu:16.04

$ apt-get update && apt-get install -y g++ kcov jq
$ cd /source && g++ -Wall -Wextra hello.cc -g -o hello
$ kcov --skip-solibs ./coverage hello

[SimonKagstrom]

Hmm... Sorry for the very late reply.

I personally use Fedora (still at 31), where this works as expected. Anyway, it's a bit surprising that the actual --skip-solibs flag causes the failure, since solib handling is sort of an add-on-feature. It relies on using LD_PRELOAD to load a special library to override dlopen.

Perhaps a thing to test, if you have the opportunity, could be to to run kcov with LD_PRELOAD=, if there for some reason is a library preloaded by default with ubuntu 20.04, i.e.,

LD_PRELOAD= kcov --skip-solibs [...]

[pfrenzel]

Unfortunately resetting LD_PRELOAD has no effect.

There are no problems with Fedora in the current version. Debian sid shows the same behaviour as Ubuntu 20.04 (no lines hit).

I've attached two outputs with debug=31.
ubuntu:16.04.log
ubuntu:20.04.log

I just found out that a program compiled with ubuntu16.04 gives the correct result with kcov under 20.04.
Under 16.04 I tested with g++-9 and always got the correct result. But when I use g++-9 in 20.04 I get again that no lines were run through.