[PATCH] Cygwin: pty: Restore nat handles in all PTY-slave instances in GDB

[Takashi Yano]

On Sun,  8 Mar 2026 20:19:21 +0900
Takashi Yano wrote:
> If non-cygwin app is started in GDB and terminating it normally,
> re-running the non-cygwin app might fail in setup_pseudoconsole().
> 
> The error is something like:
> 
> $ gdb ./winsleep
> GNU gdb (GDB) (Cygwin 15.2-1) 15.2
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> Reading symbols from ./winsleep...
> (gdb) run
> Starting program: /home/yano/winsleep
> [New Thread 49324.0x14178]
> [Thread 49324.0x14178 exited with code 0]
> [Inferior 1 (process 49324) exited normally]
> (gdb) run
> Starting program: /home/yano/winsleep
>       0 [] gdb 294 fhandler_pty_slave::setup_pseudoconsole: CreatePseudoConsole() failed. 00000057 80070057
>                            [New Thread 86480.0xfd4]
> [Thread 86480.0xfd4 exited with code 0]
> [Inferior 1 (process 86480) exited normally]
> (gdb)
> 
> The essential problem is lack of restoring nat handles for *ALL* the
> PTY-slave instances after closing pseudo console in GDB.
> 
> Restoring handles from pseudo console handles to simple pipe handles
> is not necessary in normal non-cygwin apps because pseudo console is
> setup in the stub process for the non-cygwin app and the stub process
> exits after the app is terminated.
> 
> However, for GDB, pseudo console is setup in GDB process in hooked
> CreateProcess() because GDB does not use exec() to run an inferior
> (debuggee). Therefore, after the inferior exits, nat handle must be
> restored to simple pipe handles.
> 
> The current code restores only handles in the PTY-slave instance
> that has called fhandler_pty_slave::reset_switch_to_nat_pipe(). If
> this instance is different from the instance that will setup pseudo
> console, the nat handles are not restored correctly, then call to
> CreatePseudoConsole() causes error.
> 
> To solves this issue, restore nat handles in all the PTY-slave
> instances to simple pipe handles when the inferior exits with this
> patch.
> 
> Fixes: 8aeb3f3e5037 ("Cygwin: pty: Make apps using console APIs be able to debug with gdb.")
> Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
> Reviewed-by:

This is the replacement for:
"Cygwin: pty: Use consistently first pty slave found in cygheap_fdenum"
https://cygwin.com/pipermail/cygwin-patches/2026q1/014674.html

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>