toolchain/52799: gdb can't debug live threaded processes

[martin%NetBSD.org@localhost]

>Number:         52799
>Category:       toolchain
>Synopsis:       gdb can't debug live threaded processes
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Dec 09 14:00:00 +0000 2017
>Originator:     Martin Husemann
>Release:        NetBSD 8.99.9
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: NetBSD night-owl.duskware.de 8.99.9 NetBSD 8.99.9 (NIGHT-OWL) #563: Sat Dec 9 07:57:41 CET 2017 martin%night-owl.duskware.de@localhost:/usr/src/sys/arch/amd64/compile/NIGHT-OWL amd64
Architecture: x86_64
Machine: amd64
>Description:

Running gdb -p against a firefox process (build with options debug-info
and started from $PKGOBJ/work/build/dist/bin with ./run-mozilla.sh ./firefox)
does not work well:

 > gdb -p 676
GNU gdb (GDB) 8.0.1
Copyright (C) 2017 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64--netbsd".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word".
Attaching to process 676

warning: : No such file or directory.
[New LWP 105 of process 676]
[New LWP 102 of process 676]
[New LWP 74 of process 676]
[New LWP 68 of process 676]
[New LWP 64 of process 676]
[New LWP 63 of process 676]
[New LWP 62 of process 676]
[New LWP 60 of process 676]
[New LWP 59 of process 676]
[New LWP 56 of process 676]
[New LWP 55 of process 676]
[New LWP 54 of process 676]
[New LWP 51 of process 676]
[New LWP 50 of process 676]
[New LWP 49 of process 676]
[New LWP 48 of process 676]
[New LWP 47 of process 676]
[New LWP 46 of process 676]
[New LWP 45 of process 676]
[New LWP 44 of process 676]
[New LWP 43 of process 676]
[New LWP 42 of process 676]
[New LWP 41 of process 676]
[New LWP 40 of process 676]
[New LWP 36 of process 676]
[New LWP 35 of process 676]
[New LWP 34 of process 676]
[New LWP 33 of process 676]
[New LWP 30 of process 676]
[New LWP 29 of process 676]
[New LWP 25 of process 676]
[New LWP 24 of process 676]
[New LWP 23 of process 676]
[New LWP 22 of process 676]
[New LWP 21 of process 676]
[New LWP 20 of process 676]
[New LWP 19 of process 676]
[New LWP 18 of process 676]
[New LWP 17 of process 676]
[New LWP 15 of process 676]
[New LWP 14 of process 676]
[New LWP 13 of process 676]
[New LWP 12 of process 676]
[New LWP 11 of process 676]
[New LWP 10 of process 676]
[New LWP 9 of process 676]
[New LWP 8 of process 676]
[New LWP 7 of process 676]
[New LWP 6 of process 676]
[New LWP 5 of process 676]
[New LWP 4 of process 676]
[New LWP 3 of process 676]
[New LWP 2 of process 676]
[New LWP 1 of process 676]
[Switching to LWP 106 of process 676]
0xf68a96ea in ?? ()
(gdb) c
Continuing.

and then exiting firefox (to make it crash):

[New LWP 109 of process 676]

Thread 56 stopped.
[Switching to LWP 109 of process 676]
0xf68a96ea in ?? ()
ptrace: No such process.

Disabling mprotect/aslr does not help.

>How-To-Repeat:
s/a

>Fix:
n/a