Fix race condition in cover.erl

[altenwald]

Erlang R15B02 and R16B has a race condition in cover.erl, when a project with several applications in the apps directory is launched throught rebar with eunit, often crash with this message:

ERROR: eunit failed while processing /home/manuel/Proyectos/myproject/apps/app2: {'EXIT',
    {{badmatch,
         {error,
             {badarg,
                 [{ets,new,
                      [cover_internal_data_table,
                       [set,public,named_table,{write_concurrency,true}]],
                      []},
                  {cover,init_main,1,[{file,"cover.erl"},{line,565}]}]}}},
     [{rebar_eunit,cover_init,2,[{file,"src/rebar_eunit.erl"},{line,445}]},
      {rebar_eunit,run_eunit,3,[{file,"src/rebar_eunit.erl"},{line,127}]},
      {rebar_core,run_modules,4,[{file,"src/rebar_core.erl"},{line,405}]},
      {rebar_core,execute,5,[{file,"src/rebar_core.erl"},{line,334}]},
      {rebar_core,process_dir1,6,[{file,"src/rebar_core.erl"},{line,197}]},
      {rebar_core,process_each,5,[{file,"src/rebar_core.erl"},{line,268}]},
      {rebar_core,process_dir1,6,[{file,"src/rebar_core.erl"},{line,173}]},
      {rebar_core,process_commands,2,
          [{file,"src/rebar_core.erl"},{line,61}]}]}}

Adding cover.erl to the "src" directory fix the issue.

[bfosberry]

I consistently trigger this issue with eunit and ct. I tried hooking rebar into BOTH of your repos and they both trigger the issue. @bosqueviejo, should cover.erl take effect if I plug your repo into rebar the same way I would with @idubrovs or are there any other steps I would need to take to implement the patch?

[manuel-rubio]

If you get the ets error in cover, only put the cover.erl in the dependency and launch the tests, in Erlang with flat module model, this cover module overload the cover by default.

[tsloughter]

It has been almost 5 years since anyone has commented on this and it seems to be a rebar2 specific issue so I'm going to close. If it is still important please reopen.

[manuel-rubio]

@tsloughter yes, sorry, I sent the fix for cover.erl to Erlang/OTP base code and was included in R16 so, it's should be solved/fixed a long time ago (if you are using R16+, of course).