[DynInst_API:] [dyninst/dyninst] 5d2a64: Improve detection of ghost threads (#784)

[noreply@xxxxxxxxxx]

  Branch: refs/heads/master
  Home:   https://github.com/dyninst/dyninst
  Commit: 5d2a64b894e016edc185ebba616f64bca677454d
      https://github.com/dyninst/dyninst/commit/5d2a64b894e016edc185ebba616f64bca677454d
  Author: Tim Haines <thaines.astro@xxxxxxxxx>
  Date:   2020-07-31 (Fri, 31 Jul 2020)

  Changed paths:
    M proccontrol/src/int_process.h
    M proccontrol/src/linux.C
    M proccontrol/src/linux.h
    M proccontrol/src/process.C

  Log Message:
  -----------
  Improve detection of ghost threads (#784)

Change plat_handle_ghost_thread to return 'bool' (see #742).

This indicates if the thread is actually a ghost or not. This can happen
because ptrace returned ESRCH (no such process) in
LinuxPtrace::ptrace_int, yet the process is alive. This is a valid state
for ptrace, but ptrace_int doesn't check for this. The ptrace man-page
indicates that this can happen when a process received a STOP signal,
but it hasn't transitioned to the new state yet.