toolchain/54318: gdb can not step over a fork call

[martin%NetBSD.org@localhost]

>Number:         54318
>Category:       toolchain
>Synopsis:       gdb can not step over a fork call
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jun 23 11:40:00 +0000 2019
>Originator:     Martin Husemann
>Release:        NetBSD 8.99.47
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: NetBSD seven-days-to-the-wolves.aprisoft.de 8.99.47 NetBSD 8.99.47 (GENERIC) #282: Sun Jun 23 11:18:04 CEST 2019 martin%seven-days-to-the-wolves.aprisoft.de@localhost:/work/src/sys/arch/amd64/compile/GENERIC amd64
Architecture: x86_64
Machine: amd64
>Description:

Trying to single step a program fails when you try to step over a function
that forks and runs some help program. Example from sysinst:

Breakpoint 1, gpt_read_from_disk (dev=0x71f36b235008 "vnd0", start=0,           
    len=156229632) at /work/src/usr.sbin/sysinst/arch/amd64/../../gpt.c:234
234     {
(gdb) n
238             assert(start == 0);
(gdb) 
239             assert(have_gpt);
(gdb) 
241             if (run_program(RUN_SILENT | RUN_ERROR_OK,
(gdb) 
[New process 14003]
[Detaching after fork from child process 21524]

Thread 1 "" received signal SIGTRAP, Trace/breakpoint trap.
0x000071f369c4283a in _sys___select50 () from /usr/lib/libc.so.12


>How-To-Repeat:

see above

>Fix:
n/a