NetBSD Problem Report #59027

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Date: Fri, 24 Jan 2025 11:46:39 +0000 (UTC)
From: ps@softinengines.com
Reply-To: ps@softinengines.com
To: gnats-bugs@NetBSD.org
Subject: gdb not able to debug forked child
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>Number:         59027
>Category:       toolchain
>Synopsis:       gdb not able to debug forked child
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Jan 24 11:50:00 +0000 2025
>Originator:     Peter Skvarka
>Release:        10.1
>Organization:
Soft in Engines
>Environment:
NetBSD bsd.lan 10.1 NetBSD 10.1 (GENERIC)
>Description:
Gdb cannot step through through code in forked child's code.
Cannot stop on breakpoint in forked child code.
>How-To-Repeat:
In my case it happens in multithreaded application. Note that application fork() is called from main thread in time when other threads already exists

How to repeat:

put breakpoint on fork() call, for example:
b sourcename.cpp:LINENUM

gdb stops on fork()

then:
set follow-fork-mode child

and try to step through forked child code.
The result is:
It is possible to step only one or two lines and the gdb jumps to forked parent.

I tried also to call "set follow-fork-mode child" after gdb started and before program is run, behavior is the same.
======================================
Relating problem: gdb does not stop on breakpoint in forked child code.



>Fix:
No ideas

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