Ensure that we cannot get any dangling pointers into code that has been purged. This is done by a two phase purge. At first phase all fun entries pointing into the code to purge are marked for purge. All processes trying to call these funs will be suspended and by this we avoid getting new direct references into the code. When all processes has been checked, these processes are resumed. The new purge strategy now also completely ignore the existence of indirect references to the code (funs). If such exist, they will cause bad fun exceptions to the caller, but will not prevent a soft purge or cause a kill of a process having such live references during a hard purge. This since it is impossible to give any guarantees that no processes in the system have such indirect references. Even when the system is completely clean from such references, new ones can appear via distribution and/or disk.
Functions in this module are never called, and some functions are outdated. In order to avoid confusion (and need for update), the module is now reduced to a simple dummy module.
If a module includes eunit.hrl, a parse transform adds the function test/0 on line 0 in the module. A bug in OTP-18.0 caused cover:analyse_to_file/1 to fail to insert cover data in the output file when line 0 existed in the cover data table. The bug is corrected by the commit "Fix cover output file". This commit adds a test which checks that the bug is not introduced again.
It is possible that not just the source but even the beam of a module is not available when calling analyse_to_file. For example when coverdata is imported from an old file and since then a module was removed. Before this fix cover:analyse_to_file/3 could possibly never return because of a helper process crashed with error:undef and never reply to the caller. At the same time link the helper process to cover_server so any further error won't let the caller waiting indefinitely.
OTP-8188 introduced a fix for handling last expressions in expressions like case, try and friends. However the fix did not account that some of those expressions like receive may have no clauses (only an after clause), leading to a function clause error when cover compiling code with such expressions.
The reconnect/1 test starts another node and takes down the connection to it for a while. However, it has been in observed in our daily builds that sometimes a "spontaneous" re-connection occurs. I think that it because of the call to rpc:cast/3 which internally will set the group leader for the remote process to a process on the test_server node. It seems that sometimes the group_leader/2 call will re-establish the connection. Unfortunately, I have not been able to force this to happen by inserting delays in the rpc module, so it it still just an hypothesis. However, letting the other node do the disconnection does seem to fix the problem and intuitively that should be safer way to do it because the group_leader/2 call and the disconnection will be executed sequentially on the same node instead of concurrently from two different nodes.
Cover was rewriting guard clauses as non-remote calls. That said, if a guard contains erlang:is_binary(Binary), Cover was incorrectly removing the erlang prefix which lead to errors if is_binary is not auto imported. This commit keeps the abstract format as it is.
Prior to this commit, cover relied on a simple heuristic that traverses directory from the beam file to find a source file. The heuristic was maintained with this patch but, if it fails, it fallbacks to the source value in the module compile info. In order to illustrate how it works, one of the tests that could not find its source now passes successfully (showing the source lookup is more robust).