Re: [PATCH] Fix Windows sharing_input_terminal hang

Eli Zaretskii via Gdb-patches
2023-08-22T15:44:01Z

> From: Pedro Alves <pedro@palves.net>
> Date: Tue, 22 Aug 2023 16:13:32 +0100
>
> After running a number of programs under Windows gdb and detaching
> them, I typed run in gdb, and got a hang, here:
>
> (top-gdb) bt
> #0 sharing_input_terminal (pid=4672) at /home/pedro/gdb/src/gdb/mingw-hdep.c:388
> #1 0x00007ff71a2d8678 in sharing_input_terminal (inf=0x23bf23dafb0) at /home/pedro/gdb/src/gdb/inflow.c:269
> #2 0x00007ff71a2d887b in child_terminal_save_inferior (self=0x23bf23de060) at /home/pedro/gdb/src/gdb/inflow.c:423
> #3 0x00007ff71a2c80c0 in inf_child_target::terminal_save_inferior (this=0x23bf23de060) at /home/pedro/gdb/src/gdb/inf-child.c:111
> #4 0x00007ff71a429c0f in target_terminal_is_ours_kind (desired_state=target_terminal_state::is_ours_for_output) at /home/pedro/gdb/src/gdb/target.c:1037
> #5 0x00007ff71a429e02 in target_terminal::ours_for_output () at /home/pedro/gdb/src/gdb/target.c:1094
> #6 0x00007ff71a2ccc8e in post_create_inferior (from_tty=0) at /home/pedro/gdb/src/gdb/infcmd.c:245
> #7 0x00007ff71a2cd431 in run_command_1 (args=0x0, from_tty=0, run_how=RUN_NORMAL) at /home/pedro/gdb/src/gdb/infcmd.c:502
> #8 0x00007ff71a2cd58b in run_command (args=0x0, from_tty=0) at /home/pedro/gdb/src/gdb/infcmd.c:527
>
> The problem is that the loop around GetConsoleProcessList looped
> forever, because there were exactly 10 processes to return.
> GetConsoleProcessList's documentation says:
>
> If the buffer is too small to hold all the valid process identifiers,
> the return value is the required number of array elements. The
> function will have stored no identifiers in the buffer. In this
> situation, use the return value to allocate a buffer that is large
> enough to store the entire list and call the function again.
>
> In this case, the buffer wasn't too small, it was exactly the right
> size, so we should have broken out of the loop. We didn't due to a
> "<" check that should have been "<=".

Such a lucky hang... ;-)

> That is fixed by this patch.

Thanks, LGTM.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>