Apart strict-aliasing warnings, fix the remaining warnings
generated by GCC 4.4.4 -Wall and -Wextra flags.
One major source of warnings was the in-house function my_bcmp
which (unconventionally) took pointers to unsigned characters
as the byte sequences to be compared. Since my_bcmp and bcmp
are deprecated functions whose only difference with memcmp is
the return value, every use of the function is replaced with
memcmp as the special return value wasn't actually being used
by any caller.
There were also various other warnings, mostly due to type
mismatches, missing return values, missing prototypes, dead
code (unreachable) and ignored return values.
- The arguments are properly quoted when mtr.pl calls my_safe_process but
unfortunately the all off when running with active state perl and stays
in cygwin perl.
- Extend the patch to only quote args that are not already quoted
This a redo of previous commit, will be included in next push
The problem is that safe_kill_win fails to detect a dead process. OpenProcess() will
succeed even after the process died, it will first fail after the last handle to process
is closed.
To fix the problem, check process status with GetExitCodeProcess() and consider
process to be dead if the exit code returned by this routine is not STILL_ALIVE.
Suspected reason for the failure is that safe_process.exe already runs in a job that does not allow breakaways.
The fix is to use a fallback - make newly created process the root of the new process group. This allows to kill process together with descendants via GenerateConsoleCtrlEvent (CTRL_BREAK_EVENT, pid)
perl
The problem here was the method how MTR gets its unique thread ids.
Prior to this patch, the method to do it was to maintain a global
table of pid,mtr_unique_id) pairs. The table was backed by a text
file. The table was cleaned up one in a while and dead processes leaking
unique_ids were determined with with kill(0) or with scripting tasklist
on Windows.
This method is flawed specifically on native Windows Perl. fork() is
implemented with starting a new thread, give it a syntetic negative PID
(threadID*(-1)), until this thread creates a new process with exec()
However, neither tasklist nor any other native Windows tool can cope with
negative perl PIDs. This lead to incorrect determination of dead process
and reusing already used mtr_unique_id.
The patch introduces alternative portable method of solving unique-id
problem. When a process needs a unique id in range [min...max], it just
starts to open files named min, min+1,...max in a loop . After file is
opened, we do non-blocking flock(). When flock() succeeds, process has
allocated the ID. When process dies, file is unlocked . Checks for zombies
are not necessary.
Since the change would create a co-existence problems with older version
of MTR, because of different way to calculate IDs, the default ID range
is changed from 250-299 to 300-349.
Another fix that was necessary enable --parallel option was to serialize
spawn() calls on Windows. specifically, IO redirects needed to be protected.
This patch also fixes hanging CRTL-C (as described in Bug #38629) for the
"new" MTR. The fix was already in 6.0 and is now downported.
- Allow the new process to break away from any job that this
process is part of so that it can be assigned to the new JobObject
we just created. This is safe since the new JobObject is created with
the JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE flag, making sure it will be
terminated when the last handle to it is closed(which is owned by
this process).
