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* [newlib-cygwin] Cygwin: termios: Add comments to the code refactored recently.
@ 2022-02-27 11:53 Takashi Yano
0 siblings, 0 replies; only message in thread
From: Takashi Yano @ 2022-02-27 11:53 UTC (permalink / raw)
To: cygwin-cvs
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=33d8578feb51f807e89d9592d5aaf28e88df4e0d
commit 33d8578feb51f807e89d9592d5aaf28e88df4e0d
Author: Takashi Yano <takashi.yano@nifty.ne.jp>
Date: Sun Feb 27 20:40:24 2022 +0900
Cygwin: termios: Add comments to the code refactored recently.
- This patch adds some comments to the source code whose intent may
not be clear enough from the code which is refactored recently.
Diff:
---
winsup/cygwin/fhandler.h | 13 +++++----
winsup/cygwin/fhandler_termios.cc | 60 ++++++++++++++++++++++++++++-----------
2 files changed, 52 insertions(+), 21 deletions(-)
diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index fda5a4ec9..abd62d72a 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -1902,12 +1902,15 @@ class fhandler_termios: public fhandler_base
virtual void release_input_mutex_if_necessary (void) {};
virtual void discard_input () {};
+ /* Result status of processing keys in process_sigs(). */
enum process_sig_state {
- signalled,
- not_signalled,
- not_signalled_but_done,
- not_signalled_with_nat_reader,
- done_with_debugger
+ signalled, /* Signalled normally */
+ not_signalled, /* Not signalled at all */
+ not_signalled_but_done, /* Not signalled, but CTRL_C_EVENT was sent. */
+ not_signalled_with_nat_reader, /* Not signalled, but detected non-cygwin
+ process may be reading the tty. */
+ done_with_debugger /* The key was processed (CTRL_C_EVENT was sent)
+ for inferior of GDB. */
};
public:
diff --git a/winsup/cygwin/fhandler_termios.cc b/winsup/cygwin/fhandler_termios.cc
index 767b28302..f82ac76dc 100644
--- a/winsup/cygwin/fhandler_termios.cc
+++ b/winsup/cygwin/fhandler_termios.cc
@@ -149,7 +149,8 @@ tty_min::kill_pgrp (int sig, pid_t target_pgid)
if (!p || !p->exists () || p->ctty != ntty || p->pgid != target_pgid)
continue;
if (p->process_state & PID_NOTCYGWIN)
- continue;
+ continue; /* Do not send signal to non-cygwin process to prevent
+ cmd.exe from crash. */
if (p == myself)
killself = sig != __SIGSETPGRP && !exit_state;
else
@@ -309,32 +310,52 @@ fhandler_termios::echo_erase (int force)
doecho ("\b \b", 3);
}
+/* The basic policy is as follows:
+ - The signal generated by key press will be sent only to cygwin process.
+ - For non-cygwin process, CTRL_C_EVENT will be sent on Ctrl-C. */
+/* The inferior of GDB is an exception. GDB does not support to hook signal
+ even if the inferior is a cygwin app. As a result, inferior cannot be
+ continued after interruption by Ctrl-C if SIGINT was sent. Therefore,
+ CTRL_C_EVENT rather than SIGINT is sent to the inferior of GDB. */
fhandler_termios::process_sig_state
fhandler_termios::process_sigs (char c, tty* ttyp, fhandler_termios *fh)
{
termios &ti = ttyp->ti;
pid_t pgid = ttyp->pgid;
+ /* The name *_nat stands for 'native' which means non-cygwin apps. */
pinfo leader (pgid);
- bool cyg_leader = leader && !(leader->process_state & PID_NOTCYGWIN);
+ bool cyg_leader = /* The process leader is a cygwin process. */
+ leader && !(leader->process_state & PID_NOTCYGWIN);
bool ctrl_c_event_sent = false;
bool need_discard_input = false;
- bool pg_with_nat = false;
- bool need_send_sig = false;
- bool nat_shell = false;
- bool cyg_reader = false;
- bool with_debugger = false;
- bool with_debugger_nat = false;
+ bool pg_with_nat = false; /* The process group has non-cygwin processes. */
+ bool need_send_sig = false; /* There is process which need the signal. */
+ bool nat_shell = false; /* The shell seems to be a non-cygwin process. */
+ bool cyg_reader = false; /* Cygwin process is reading the tty. */
+ bool with_debugger = false; /* GDB is debugging cygwin app. */
+ bool with_debugger_nat = false; /* GDB is debugging non-cygwin app. */
winpids pids ((DWORD) 0);
for (unsigned i = 0; i < pids.npids; i++)
{
_pinfo *p = pids[i];
+ /* PID_NOTCYGWIN: check this for non-cygwin process.
+ PID_NEW_PG: check this ofr GDB with non-cygwin inferior in pty
+ without pcon enabled. In this case, the inferior is not
+ cygwin process list. PID_NEW_PG is set as a marker for
+ GDB with non-cygwin inferior in pty code.
+ !PID_CYGPARENT: check this for GDB with cygwin inferior. */
if (c == '\003' && p && p->ctty == ttyp->ntty && p->pgid == pgid
&& ((p->process_state & PID_NOTCYGWIN)
|| (p->process_state & PID_NEW_PG)
|| !(p->process_state & PID_CYGPARENT)))
{
+ /* Ctrl-C event will be sent only to the processes attaching
+ to the same console. Therefore, attach to the console to
+ which the target process is attaching before sending the
+ CTRL_C_EVENT. After sending the event, reattach to the
+ console to which the process was previously attached. */
pinfo pinfo_resume = pinfo (myself->ppid);
DWORD resume_pid = 0;
if (pinfo_resume)
@@ -361,7 +382,8 @@ fhandler_termios::process_sigs (char c, tty* ttyp, fhandler_termios *fh)
&& (p->process_state & PID_NOTCYGWIN))
GenerateConsoleCtrlEvent (CTRL_BREAK_EVENT, p->dwProcessId);
else if ((!fh || fh->need_send_ctrl_c_event () || cyg_leader)
- && !ctrl_c_event_sent)
+ && !ctrl_c_event_sent) /* cyg_leader is needed by GDB
+ with non-cygwin inferior */
{
GenerateConsoleCtrlEvent (CTRL_C_EVENT, 0);
ctrl_c_event_sent = true;
@@ -378,13 +400,13 @@ fhandler_termios::process_sigs (char c, tty* ttyp, fhandler_termios *fh)
if (p && p->ctty == ttyp->ntty && p->pgid == pgid)
{
if (p->process_state & PID_NOTCYGWIN)
- pg_with_nat = true;
+ pg_with_nat = true; /* The process group has non-cygwin process */
if (!(p->process_state & PID_NOTCYGWIN))
- need_send_sig = true;
+ need_send_sig = true; /* Process which needs signal exists */
if (!p->cygstarted)
- nat_shell = true;
+ nat_shell = true; /* The shell seems to a non-cygwin shell */
if (p->process_state & PID_TTYIN)
- cyg_reader = true;
+ cyg_reader = true; /* Theh process is reading the tty */
if (!p->cygstarted && !(p->process_state & PID_NOTCYGWIN)
&& (p != myself || being_debugged ())
&& cyg_leader) /* inferior is cygwin app */
@@ -406,8 +428,12 @@ fhandler_termios::process_sigs (char c, tty* ttyp, fhandler_termios *fh)
return done_with_debugger;
}
if (with_debugger_nat)
- return not_signalled;
- /* Send SIGQUIT to non-cygwin process. */
+ return not_signalled; /* Do not process slgnal keys further.
+ The non-cygwin inferior of GDB cannot receive
+ the signals. */
+ /* Send SIGQUIT to non-cygwin process. Non-cygwin app will not be alerted
+ by kill_pgrp(), however, QUIT key should quit the non-cygwin app
+ if it is started along with cygwin process from cygwin shell. */
if ((ti.c_lflag & ISIG) && CCEQ (ti.c_cc[VQUIT], c)
&& pg_with_nat && need_send_sig && !nat_shell)
{
@@ -426,7 +452,9 @@ fhandler_termios::process_sigs (char c, tty* ttyp, fhandler_termios *fh)
sig = SIGINT;
else if (CCEQ (ti.c_cc[VQUIT], c))
sig = SIGQUIT;
- else if (pg_with_nat)
+ else if (pg_with_nat) /* If the process group has a non-cygwin process,
+ it cannot be suspended correctly. Therefore,
+ do not send SIGTSTP. */
goto not_a_sig;
else if (CCEQ (ti.c_cc[VSUSP], c))
sig = SIGTSTP;
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