Normally, on linux we retrieve the process ID from the LinuxProcStatus
stream (which is just the contents of /proc/%d/status pseudo-file).
However, this stream is not strictly required (it's a breakpad
extension), and we are encountering a fair amount of minidumps which do
not have it present. It's not clear whether this is the case with all
these minidumps, but the two known situations where this stream can be
- /proc filesystem not mounted (or something to that effect)
- process crashing after exhausting (almost) all file descriptors (so the minidump writer may not be able to open the /proc file)
At first I wanted to do something similar to what the gdb-remote plugin
does when talking to bare metal gdb stubs and like, and "invent" a
process ID in this case. However, then I noticed that most of the things
"just work" even if I leave the proces ID as "invalid".
Since it seems we have multiple use cases for a "process" without a
"process id", what I do in this patch instead is "downgrade" the missing
pid case to a warning. I also changes the "process status" output to
better handle the case of a missing/unknown pid.
The test case in this patch verifies that basic functionality still
works even with a pid-less minidump.