[PATCH] [RFC] Don't propagate our current terminal state to the inferior

[PATCH] [RFC] Don't propagate our current terminal state to the inferior

[Patrick Palka]

Currently when we start an inferior we have the inferior inherit our
terminal state.  Under TUI, our terminal is highly modified by ncurses
and readline.  So when starting an inferior under TUI, the inferior will
have a highly modified terminal state which will interfere with standard
I/O. For example,

$ gdb gdb
(gdb) break main
(gdb) run
(gdb) print puts ("a\nb")
a
b
$1 = 4
(gdb) [enter TUI mode]
(gdb) run
(gdb) [exit TUI mode]
(gdb) print puts ("a\nb")
a
 b
  $2 = 4
(gdb) print puts ("a\r\nb\r")
a
b
$3 = 6

As you can see, when we start the inferior under the regular interface,
puts() prints the text properly.  But when we start the inferior under
TUI, puts() does not print the text properly.  This is because when we
start the inferior under TUI it inherits our current terminal state
which has been modified by ncurses to, among other things, require an
explicit \r\n to print a new line. As a result the inferior performs
standard I/O in an unexpected way.

Because of this discrepancy, it doesn't seem like a good idea to have
the inferior inherit our _current_ terminal state for it may have been
modified by readline and/or ncurses.  Instead, we should have the
inferior inherit a pristine snapshot of our terminal state taken before
readline or ncurses have had a chance to alter it.  This enables the
inferior to run in a more accurate way, more closely mimicking its
behavior had the program run standalone.  And it fixes the above
mentioned issue.

I wonder, does this change make sense?  What do others think?

Tested on x86_64-unknown-linux-gnu.

	* terminal.h (set_initial_inferior_ttystate): Declare.
	* inflow.c (initial_inferior_ttystate): New static variable.
	(set_initial_inferior_ttystate): New setter.
	(child_terminal_init_with_pgrp): Copy initial_inferior_ttystate
	instead of our current terminal state.
	* top.c (gdb_init): Call set_initial_inferior_ttystate.
---
 gdb/inflow.c   | 13 ++++++++++++-
 gdb/terminal.h |  2 ++
 gdb/top.c      |  4 ++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/gdb/inflow.c b/gdb/inflow.c
index 8902174..7b432ad 100644
--- a/gdb/inflow.c
+++ b/gdb/inflow.c
@@ -79,6 +79,10 @@ struct terminal_info
    unimportant.  */
 static struct terminal_info our_terminal_info;
 
+/* The initial tty state given to each new inferior.  It is a snapshot of our
+   own tty state taken during initialization of GDB.  */
+static serial_ttystate initial_inferior_ttystate;
+
 static struct terminal_info *get_inflow_inferior_data (struct inferior *);
 
 #ifdef PROCESS_GROUP_TYPE
@@ -156,6 +160,13 @@ show_interactive_mode (struct ui_file *file, int from_tty,
     fprintf_filtered (file, "Debugger's interactive mode is %s.\n", value);
 }
 
+/* Set the initial tty state that is to be inherited by new inferiors.  */
+void
+set_initial_inferior_ttystate (void)
+{
+  initial_inferior_ttystate = serial_get_tty_state (stdin_serial);
+}
+
 /* Does GDB have a terminal (on stdin)?  */
 int
 gdb_has_a_terminal (void)
@@ -227,7 +238,7 @@ child_terminal_init_with_pgrp (int pgrp)
     {
       xfree (tinfo->ttystate);
       tinfo->ttystate = serial_copy_tty_state (stdin_serial,
-					       our_terminal_info.ttystate);
+					       initial_inferior_ttystate);
 
       /* Make sure that next time we call terminal_inferior (which will be
          before the program runs, as it needs to be), we install the new
diff --git a/gdb/terminal.h b/gdb/terminal.h
index 433aa7d..186bce2 100644
--- a/gdb/terminal.h
+++ b/gdb/terminal.h
@@ -103,6 +103,8 @@ extern int gdb_has_a_terminal (void);
 
 extern void gdb_save_tty_state (void);
 
+extern void set_initial_inferior_ttystate (void);
+
 /* Set the process group of the caller to its own pid, or do nothing
    if we lack job control.  */
 extern int gdb_setpgid (void);
diff --git a/gdb/top.c b/gdb/top.c
index 83d858a..c4b5c2c 100644
--- a/gdb/top.c
+++ b/gdb/top.c
@@ -1886,6 +1886,10 @@ gdb_init (char *argv0)
 
   initialize_stdin_serial ();
 
+  /* Take a snapshot of our tty state before readline/ncurses have had a chance
+     to alter it.  */
+  set_initial_inferior_ttystate ();
+
   async_init_signals ();
 
   /* We need a default language for parsing expressions, so simple
-- 
2.2.0.rc1.23.gf570943

Re: [PATCH] [RFC] Don't propagate our current terminal state to the inferior

[Joel Brobecker]

> Currently when we start an inferior we have the inferior inherit our
> terminal state.  Under TUI, our terminal is highly modified by ncurses
> and readline.  So when starting an inferior under TUI, the inferior will
> have a highly modified terminal state which will interfere with standard
> I/O. For example,
> 
> $ gdb gdb
> (gdb) break main
> (gdb) run
> (gdb) print puts ("a\nb")
> a
> b
> $1 = 4
> (gdb) [enter TUI mode]
> (gdb) run
> (gdb) [exit TUI mode]
> (gdb) print puts ("a\nb")
> a
>  b
>   $2 = 4
> (gdb) print puts ("a\r\nb\r")
> a
> b
> $3 = 6
> 
> As you can see, when we start the inferior under the regular interface,
> puts() prints the text properly.  But when we start the inferior under
> TUI, puts() does not print the text properly.  This is because when we
> start the inferior under TUI it inherits our current terminal state
> which has been modified by ncurses to, among other things, require an
> explicit \r\n to print a new line. As a result the inferior performs
> standard I/O in an unexpected way.
> 
> Because of this discrepancy, it doesn't seem like a good idea to have
> the inferior inherit our _current_ terminal state for it may have been
> modified by readline and/or ncurses.  Instead, we should have the
> inferior inherit a pristine snapshot of our terminal state taken before
> readline or ncurses have had a chance to alter it.  This enables the
> inferior to run in a more accurate way, more closely mimicking its
> behavior had the program run standalone.  And it fixes the above
> mentioned issue.
> 
> I wonder, does this change make sense?  What do others think?

FWIW: It does make sense to me, but I have been known to have a really
superficial view or how terminals work. I'd be more comfortable if you
waited for someone like Pedro to give it a second look. If no one
reviews it by, say, Dec 8th, can you ping me again?

Thank you,
-- 
Joel

Re: [PATCH] [RFC] Don't propagate our current terminal state to the inferior

[Patrick Palka]

On Sat, Nov 22, 2014 at 3:39 PM, Patrick Palka <patrick@parcs.ath.cx> wrote:
> Currently when we start an inferior we have the inferior inherit our
> terminal state.  Under TUI, our terminal is highly modified by ncurses
> and readline.  So when starting an inferior under TUI, the inferior will
> have a highly modified terminal state which will interfere with standard
> I/O. For example,
>
> $ gdb gdb
> (gdb) break main
> (gdb) run
> (gdb) print puts ("a\nb")
> a
> b
> $1 = 4
> (gdb) [enter TUI mode]
> (gdb) run
> (gdb) [exit TUI mode]
> (gdb) print puts ("a\nb")
> a
>  b
>   $2 = 4
> (gdb) print puts ("a\r\nb\r")
> a
> b
> $3 = 6
>
> As you can see, when we start the inferior under the regular interface,
> puts() prints the text properly.  But when we start the inferior under
> TUI, puts() does not print the text properly.  This is because when we
> start the inferior under TUI it inherits our current terminal state
> which has been modified by ncurses to, among other things, require an
> explicit \r\n to print a new line. As a result the inferior performs
> standard I/O in an unexpected way.
>
> Because of this discrepancy, it doesn't seem like a good idea to have
> the inferior inherit our _current_ terminal state for it may have been
> modified by readline and/or ncurses.  Instead, we should have the
> inferior inherit a pristine snapshot of our terminal state taken before
> readline or ncurses have had a chance to alter it.  This enables the
> inferior to run in a more accurate way, more closely mimicking its
> behavior had the program run standalone.  And it fixes the above
> mentioned issue.
>
> I wonder, does this change make sense?  What do others think?
>
> Tested on x86_64-unknown-linux-gnu.
>
>         * terminal.h (set_initial_inferior_ttystate): Declare.
>         * inflow.c (initial_inferior_ttystate): New static variable.
>         (set_initial_inferior_ttystate): New setter.
>         (child_terminal_init_with_pgrp): Copy initial_inferior_ttystate
>         instead of our current terminal state.
>         * top.c (gdb_init): Call set_initial_inferior_ttystate.
> ---
>  gdb/inflow.c   | 13 ++++++++++++-
>  gdb/terminal.h |  2 ++
>  gdb/top.c      |  4 ++++
>  3 files changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/gdb/inflow.c b/gdb/inflow.c
> index 8902174..7b432ad 100644
> --- a/gdb/inflow.c
> +++ b/gdb/inflow.c
> @@ -79,6 +79,10 @@ struct terminal_info
>     unimportant.  */
>  static struct terminal_info our_terminal_info;
>
> +/* The initial tty state given to each new inferior.  It is a snapshot of our
> +   own tty state taken during initialization of GDB.  */
> +static serial_ttystate initial_inferior_ttystate;
> +
>  static struct terminal_info *get_inflow_inferior_data (struct inferior *);
>
>  #ifdef PROCESS_GROUP_TYPE
> @@ -156,6 +160,13 @@ show_interactive_mode (struct ui_file *file, int from_tty,
>      fprintf_filtered (file, "Debugger's interactive mode is %s.\n", value);
>  }
>
> +/* Set the initial tty state that is to be inherited by new inferiors.  */
> +void
> +set_initial_inferior_ttystate (void)
> +{
> +  initial_inferior_ttystate = serial_get_tty_state (stdin_serial);
> +}
> +
>  /* Does GDB have a terminal (on stdin)?  */
>  int
>  gdb_has_a_terminal (void)
> @@ -227,7 +238,7 @@ child_terminal_init_with_pgrp (int pgrp)
>      {
>        xfree (tinfo->ttystate);
>        tinfo->ttystate = serial_copy_tty_state (stdin_serial,
> -                                              our_terminal_info.ttystate);
> +                                              initial_inferior_ttystate);
>
>        /* Make sure that next time we call terminal_inferior (which will be
>           before the program runs, as it needs to be), we install the new
> diff --git a/gdb/terminal.h b/gdb/terminal.h
> index 433aa7d..186bce2 100644
> --- a/gdb/terminal.h
> +++ b/gdb/terminal.h
> @@ -103,6 +103,8 @@ extern int gdb_has_a_terminal (void);
>
>  extern void gdb_save_tty_state (void);
>
> +extern void set_initial_inferior_ttystate (void);
> +
>  /* Set the process group of the caller to its own pid, or do nothing
>     if we lack job control.  */
>  extern int gdb_setpgid (void);
> diff --git a/gdb/top.c b/gdb/top.c
> index 83d858a..c4b5c2c 100644
> --- a/gdb/top.c
> +++ b/gdb/top.c
> @@ -1886,6 +1886,10 @@ gdb_init (char *argv0)
>
>    initialize_stdin_serial ();
>
> +  /* Take a snapshot of our tty state before readline/ncurses have had a chance
> +     to alter it.  */
> +  set_initial_inferior_ttystate ();
> +
>    async_init_signals ();
>
>    /* We need a default language for parsing expressions, so simple
> --
> 2.2.0.rc1.23.gf570943
>

Ping.

Re: [PATCH] [RFC] Don't propagate our current terminal state to the inferior

[Pedro Alves]

On 11/22/2014 08:39 PM, Patrick Palka wrote:
> Currently when we start an inferior we have the inferior inherit our
> terminal state.  Under TUI, our terminal is highly modified by ncurses
> and readline.  So when starting an inferior under TUI, the inferior will
> have a highly modified terminal state which will interfere with standard
> I/O. For example,
> 
> $ gdb gdb
> (gdb) break main
> (gdb) run
> (gdb) print puts ("a\nb")
> a
> b
> $1 = 4
> (gdb) [enter TUI mode]
> (gdb) run
> (gdb) [exit TUI mode]
> (gdb) print puts ("a\nb")
> a
>  b
>   $2 = 4
> (gdb) print puts ("a\r\nb\r")
> a
> b
> $3 = 6
> 
> As you can see, when we start the inferior under the regular interface,
> puts() prints the text properly.  But when we start the inferior under
> TUI, puts() does not print the text properly.  This is because when we
> start the inferior under TUI it inherits our current terminal state
> which has been modified by ncurses to, among other things, require an
> explicit \r\n to print a new line. As a result the inferior performs
> standard I/O in an unexpected way.
> 
> Because of this discrepancy, it doesn't seem like a good idea to have
> the inferior inherit our _current_ terminal state for it may have been
> modified by readline and/or ncurses.  Instead, we should have the
> inferior inherit a pristine snapshot of our terminal state taken before
> readline or ncurses have had a chance to alter it.  This enables the
> inferior to run in a more accurate way, more closely mimicking its
> behavior had the program run standalone.  And it fixes the above
> mentioned issue.
> 
> I wonder, does this change make sense?  What do others think?

Thanks.  This makes sense to me.

>  
> +/* The initial tty state given to each new inferior.  It is a snapshot of our
> +   own tty state taken during initialization of GDB.  */
> +static serial_ttystate initial_inferior_ttystate;
> +
>  static struct terminal_info *get_inflow_inferior_data (struct inferior *);
>  
>  #ifdef PROCESS_GROUP_TYPE
> @@ -156,6 +160,13 @@ show_interactive_mode (struct ui_file *file, int from_tty,
>      fprintf_filtered (file, "Debugger's interactive mode is %s.\n", value);
>  }
>  
> +/* Set the initial tty state that is to be inherited by new inferiors.  */
> +void
> +set_initial_inferior_ttystate (void)
> +{
> +  initial_inferior_ttystate = serial_get_tty_state (stdin_serial);
> +}

"initial inferior" reminded me of the initial inferior that
GDB always creates.  E.g., in main.c:

  /* Now that gdb_init has created the initial inferior, we're in
     position to set args for that inferior.  */


Could you rename the function and the variable?  Like:

set_initial_gdb_ttystate (void)
{
  initial_gdb_ttystate = serial_get_tty_state (stdin_serial);
}

...

/* Snapshot of our own tty state taken during initialization
   of GDB.  This is used as tty state given to each new inferior.  */
static serial_ttystate initial_gdb_ttystate;



Calling the variable that way calls it for what it holds, not
for how it is used, which is friendlier to reuse in
other situations.

This would be OK with me with that change.

Thanks,
Pedro Alves

Re: [PATCH] [RFC] Don't propagate our current terminal state to the inferior

[Patrick Palka]

On Wed, 7 Jan 2015, Pedro Alves wrote:

> On 11/22/2014 08:39 PM, Patrick Palka wrote:
>> Currently when we start an inferior we have the inferior inherit our
>> terminal state.  Under TUI, our terminal is highly modified by ncurses
>> and readline.  So when starting an inferior under TUI, the inferior will
>> have a highly modified terminal state which will interfere with standard
>> I/O. For example,
>>
>> $ gdb gdb
>> (gdb) break main
>> (gdb) run
>> (gdb) print puts ("a\nb")
>> a
>> b
>> $1 = 4
>> (gdb) [enter TUI mode]
>> (gdb) run
>> (gdb) [exit TUI mode]
>> (gdb) print puts ("a\nb")
>> a
>>  b
>>   $2 = 4
>> (gdb) print puts ("a\r\nb\r")
>> a
>> b
>> $3 = 6
>>
>> As you can see, when we start the inferior under the regular interface,
>> puts() prints the text properly.  But when we start the inferior under
>> TUI, puts() does not print the text properly.  This is because when we
>> start the inferior under TUI it inherits our current terminal state
>> which has been modified by ncurses to, among other things, require an
>> explicit \r\n to print a new line. As a result the inferior performs
>> standard I/O in an unexpected way.
>>
>> Because of this discrepancy, it doesn't seem like a good idea to have
>> the inferior inherit our _current_ terminal state for it may have been
>> modified by readline and/or ncurses.  Instead, we should have the
>> inferior inherit a pristine snapshot of our terminal state taken before
>> readline or ncurses have had a chance to alter it.  This enables the
>> inferior to run in a more accurate way, more closely mimicking its
>> behavior had the program run standalone.  And it fixes the above
>> mentioned issue.
>>
>> I wonder, does this change make sense?  What do others think?
>
> Thanks.  This makes sense to me.
>
>>
>> +/* The initial tty state given to each new inferior.  It is a snapshot of our
>> +   own tty state taken during initialization of GDB.  */
>> +static serial_ttystate initial_inferior_ttystate;
>> +
>>  static struct terminal_info *get_inflow_inferior_data (struct inferior *);
>>
>>  #ifdef PROCESS_GROUP_TYPE
>> @@ -156,6 +160,13 @@ show_interactive_mode (struct ui_file *file, int from_tty,
>>      fprintf_filtered (file, "Debugger's interactive mode is %s.\n", value);
>>  }
>>
>> +/* Set the initial tty state that is to be inherited by new inferiors.  */
>> +void
>> +set_initial_inferior_ttystate (void)
>> +{
>> +  initial_inferior_ttystate = serial_get_tty_state (stdin_serial);
>> +}
>
> "initial inferior" reminded me of the initial inferior that
> GDB always creates.  E.g., in main.c:
>
>  /* Now that gdb_init has created the initial inferior, we're in
>     position to set args for that inferior.  */
>
>
> Could you rename the function and the variable?  Like:
>
> set_initial_gdb_ttystate (void)
> {
>  initial_gdb_ttystate = serial_get_tty_state (stdin_serial);
> }
>
> ...
>
> /* Snapshot of our own tty state taken during initialization
>   of GDB.  This is used as tty state given to each new inferior.  */
> static serial_ttystate initial_gdb_ttystate;
>
>
>
> Calling the variable that way calls it for what it holds, not
> for how it is used, which is friendlier to reuse in
> other situations.
>
> This would be OK with me with that change.
>
> Thanks,
> Pedro Alves
>
>

Thanks Pedro.  I have changed the names of the new function and variable
and committed the patch.  Please let me know if I have messed up the
commit procedure.

Final patch:

-- >8 --

Subject: [PATCH] Don't propagate our current terminal state to the inferior

Currently when we start an inferior we have the inferior inherit our
terminal state.  Under TUI, our terminal is highly modified by ncurses
and readline.  So when starting an inferior under TUI, the inferior will
have a highly modified terminal state which will interfere with standard
I/O. For example,

$ gdb gdb
(gdb) break main
(gdb) run
(gdb) print puts ("a\nb")
a
b
$1 = 4
(gdb) [enter TUI mode]
(gdb) run
(gdb) [exit TUI mode]
(gdb) print puts ("a\nb")
a
  b
   $2 = 4
(gdb) print puts ("a\r\nb\r")
a
b
$3 = 6

As you can see, when we start the inferior under the regular interface,
puts() prints the text properly.  But when we start the inferior under
TUI, puts() does not print the text properly.  This is because when we
start the inferior under TUI it inherits our current terminal state
which has been modified by ncurses to, among other things, require an
explicit \r\n to print a new line. As a result the inferior performs
standard I/O in an unexpected way.

Because of this discrepancy, it doesn't seem like a good idea to have
the inferior inherit our _current_ terminal state for it may have been
modified by readline and/or ncurses.  Instead, we should have the
inferior inherit a pristine snapshot of our terminal state taken before
readline or ncurses have had a chance to alter it.  This enables the
inferior to run in a more accurate way, more closely mimicking the
program's behavior had it run standalone.  And it fixes the above
mentioned issue.

Tested on x86_64-unknown-linux-gnu.

gdb/ChangeLog:

 	* terminal.h (set_initial_gdb_ttystate): Declare.
 	* inflow.c (initial_gdb_ttystate): New static variable.
 	(set_initial_gdb_ttystate): New setter.
 	(child_terminal_init_with_pgrp): Copy initial_gdb_ttystate
 	instead of our current terminal state.
 	* top.c (gdb_init): Call set_initial_gdb_ttystate.
---
  gdb/ChangeLog  |  9 +++++++++
  gdb/inflow.c   | 13 ++++++++++++-
  gdb/terminal.h |  2 ++
  gdb/top.c      |  4 ++++
  4 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0b63d34..6477dc1 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,12 @@
+2015-01-07  Patrick Palka  <patrick@parcs.ath.cx>
+
+	* terminal.h (set_initial_gdb_ttystate): Declare.
+	* inflow.c (initial_gdb_ttystate): New static variable.
+	(set_initial_gdb_ttystate): New setter.
+	(child_terminal_init_with_pgrp): Copy initial_gdb_ttystate
+	instead of our current terminal state.
+	* top.c (gdb_init): Call set_initial_gdb_ttystate.
+
  2015-01-07  Joel Brobecker  <brobecker@adacore.com>

  	* guile/scm-type.c (tyscm_array_1): Add comment.
diff --git a/gdb/inflow.c b/gdb/inflow.c
index 8947e63..3c121a3 100644
--- a/gdb/inflow.c
+++ b/gdb/inflow.c
@@ -79,6 +79,10 @@ struct terminal_info
     unimportant.  */
  static struct terminal_info our_terminal_info;

+/* The initial tty state given to each new inferior.  It is a snapshot of our
+   own tty state taken during initialization of GDB.  */
+static serial_ttystate initial_gdb_ttystate;
+
  static struct terminal_info *get_inflow_inferior_data (struct inferior *);

  #ifdef PROCESS_GROUP_TYPE
@@ -156,6 +160,13 @@ show_interactive_mode (struct ui_file *file, int from_tty,
      fprintf_filtered (file, "Debugger's interactive mode is %s.\n", value);
  }

+/* Set the initial tty state that is to be inherited by new inferiors.  */
+void
+set_initial_gdb_ttystate (void)
+{
+  initial_gdb_ttystate = serial_get_tty_state (stdin_serial);
+}
+
  /* Does GDB have a terminal (on stdin)?  */
  int
  gdb_has_a_terminal (void)
@@ -227,7 +238,7 @@ child_terminal_init_with_pgrp (int pgrp)
      {
        xfree (tinfo->ttystate);
        tinfo->ttystate = serial_copy_tty_state (stdin_serial,
-					       our_terminal_info.ttystate);
+					       initial_gdb_ttystate);

        /* Make sure that next time we call terminal_inferior (which will be
           before the program runs, as it needs to be), we install the new
diff --git a/gdb/terminal.h b/gdb/terminal.h
index ae25c98..17acde2 100644
--- a/gdb/terminal.h
+++ b/gdb/terminal.h
@@ -103,6 +103,8 @@ extern int gdb_has_a_terminal (void);

  extern void gdb_save_tty_state (void);

+extern void set_initial_gdb_ttystate (void);
+
  /* Set the process group of the caller to its own pid, or do nothing
     if we lack job control.  */
  extern int gdb_setpgid (void);
diff --git a/gdb/top.c b/gdb/top.c
index 524a92b..b85ea1a 100644
--- a/gdb/top.c
+++ b/gdb/top.c
@@ -1890,6 +1890,10 @@ gdb_init (char *argv0)

    initialize_stdin_serial ();

+  /* Take a snapshot of our tty state before readline/ncurses have had a chance
+     to alter it.  */
+  set_initial_gdb_ttystate ();
+
    async_init_signals ();

    /* We need a default language for parsing expressions, so simple
-- 
2.2.1.212.gc5b9256

Re: [PATCH] [RFC] Don't propagate our current terminal state to the inferior

[Joel Brobecker]

[-- Attachment #1: Type: text/plain, Size: 801 bytes --]

> gdb/ChangeLog:
> 
> 	* terminal.h (set_initial_gdb_ttystate): Declare.
> 	* inflow.c (initial_gdb_ttystate): New static variable.
> 	(set_initial_gdb_ttystate): New setter.
> 	(child_terminal_init_with_pgrp): Copy initial_gdb_ttystate
> 	instead of our current terminal state.
> 	* top.c (gdb_init): Call set_initial_gdb_ttystate.

Small nit that I noticed just as I glanced at the patch...

> +/* Set the initial tty state that is to be inherited by new inferiors.  */
> +void
> +set_initial_gdb_ttystate (void)
> +{

We ask that an empty line between the function's documentation
and its implementation be inserted.

I have pushed the attached patch as obvious...

gdb/ChangeLog:

        * inflow.c (set_initial_gdb_ttystate): Add empty line after
        comment documenting function.

-- 
Joel

[-- Attachment #2: 0001-Empty-line-after-comment-documenting-set_initial_gdb.patch --]
[-- Type: text/x-diff, Size: 1151 bytes --]

From ea42d6f8d1e24403e533e5dfea18e94c47ac534b Mon Sep 17 00:00:00 2001
From: Joel Brobecker <brobecker@adacore.com>
Date: Wed, 7 Jan 2015 18:49:49 +0400
Subject: [PATCH] Empty line after comment documenting
 set_initial_gdb_ttystate.

gdb/ChangeLog:

        * inflow.c (set_initial_gdb_ttystate): Add empty line after
        comment documenting function.
---
 gdb/ChangeLog | 5 +++++
 gdb/inflow.c  | 1 +
 2 files changed, 6 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 6477dc1..e9b0377 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2015-01-07  Joel Brobecker  <brobecker@adacore.com>
+
+	* inflow.c (set_initial_gdb_ttystate): Add empty line after
+	comment documenting function.
+
 2015-01-07  Patrick Palka  <patrick@parcs.ath.cx>
 
 	* terminal.h (set_initial_gdb_ttystate): Declare.
diff --git a/gdb/inflow.c b/gdb/inflow.c
index 3c121a3..4c81a68 100644
--- a/gdb/inflow.c
+++ b/gdb/inflow.c
@@ -161,6 +161,7 @@ show_interactive_mode (struct ui_file *file, int from_tty,
 }
 
 /* Set the initial tty state that is to be inherited by new inferiors.  */
+
 void
 set_initial_gdb_ttystate (void)
 {
-- 
1.9.1

Re: [PATCH] [RFC] Don't propagate our current terminal state to the inferior

[Joel Brobecker]

> We ask that an empty line between the function's documentation
> and its implementation be inserted.

And I meant to actually paste the reference:
https://sourceware.org/gdb/wiki/Internals%20GDB-C-Coding-Standards#Document_Every_Subprogram

-- 
Joel

Re: [PATCH] [RFC] Don't propagate our current terminal state to the inferior

[Patrick Palka]

On Wed, Jan 7, 2015 at 9:57 AM, Joel Brobecker <brobecker@adacore.com> wrote:
>> We ask that an empty line between the function's documentation
>> and its implementation be inserted.
>
> And I meant to actually paste the reference:
> https://sourceware.org/gdb/wiki/Internals%20GDB-C-Coding-Standards#Document_Every_Subprogram

Good to know.  Thanks Joel.

>
> --
> Joel

Re: [PATCH] [RFC] Don't propagate our current terminal state to the inferior

[Patrick Palka]

On Wed, 7 Jan 2015, Pedro Alves wrote:

> On 11/22/2014 08:39 PM, Patrick Palka wrote:
>> Currently when we start an inferior we have the inferior inherit our
>> terminal state.  Under TUI, our terminal is highly modified by ncurses
>> and readline.  So when starting an inferior under TUI, the inferior will
>> have a highly modified terminal state which will interfere with standard
>> I/O. For example,
>>
>> $ gdb gdb
>> (gdb) break main
>> (gdb) run
>> (gdb) print puts ("a\nb")
>> a
>> b
>> $1 = 4
>> (gdb) [enter TUI mode]
>> (gdb) run
>> (gdb) [exit TUI mode]
>> (gdb) print puts ("a\nb")
>> a
>>  b
>>   $2 = 4
>> (gdb) print puts ("a\r\nb\r")
>> a
>> b
>> $3 = 6
>>
>> As you can see, when we start the inferior under the regular interface,
>> puts() prints the text properly.  But when we start the inferior under
>> TUI, puts() does not print the text properly.  This is because when we
>> start the inferior under TUI it inherits our current terminal state
>> which has been modified by ncurses to, among other things, require an
>> explicit \r\n to print a new line. As a result the inferior performs
>> standard I/O in an unexpected way.
>>
>> Because of this discrepancy, it doesn't seem like a good idea to have
>> the inferior inherit our _current_ terminal state for it may have been
>> modified by readline and/or ncurses.  Instead, we should have the
>> inferior inherit a pristine snapshot of our terminal state taken before
>> readline or ncurses have had a chance to alter it.  This enables the
>> inferior to run in a more accurate way, more closely mimicking its
>> behavior had the program run standalone.  And it fixes the above
>> mentioned issue.
>>
>> I wonder, does this change make sense?  What do others think?
>
> Thanks.  This makes sense to me.
>
>>
>> +/* The initial tty state given to each new inferior.  It is a snapshot of our
>> +   own tty state taken during initialization of GDB.  */
>> +static serial_ttystate initial_inferior_ttystate;
>> +
>>  static struct terminal_info *get_inflow_inferior_data (struct inferior *);
>>
>>  #ifdef PROCESS_GROUP_TYPE
>> @@ -156,6 +160,13 @@ show_interactive_mode (struct ui_file *file, int from_tty,
>>      fprintf_filtered (file, "Debugger's interactive mode is %s.\n", value);
>>  }
>>
>> +/* Set the initial tty state that is to be inherited by new inferiors.  */
>> +void
>> +set_initial_inferior_ttystate (void)
>> +{
>> +  initial_inferior_ttystate = serial_get_tty_state (stdin_serial);
>> +}
>
> "initial inferior" reminded me of the initial inferior that
> GDB always creates.  E.g., in main.c:
>
>  /* Now that gdb_init has created the initial inferior, we're in
>     position to set args for that inferior.  */
>
>
> Could you rename the function and the variable?  Like:
>
> set_initial_gdb_ttystate (void)
> {
>  initial_gdb_ttystate = serial_get_tty_state (stdin_serial);
> }
>
> ...
>
> /* Snapshot of our own tty state taken during initialization
>   of GDB.  This is used as tty state given to each new inferior.  */

I noticed that I forgot to accordingly update the comment for
initial_gdb_ttystate as you suggested.  I have committed this trivial
patch under the "obvious" rule:

-- >8 --

Subject: [PATCH] Trivially tweak the comment documenting
  initial_gdb_ttystate

gdb/ChangeLog:

 	* inflow.c (initial_gdb_ttystate): Tweak comment.
---
  gdb/ChangeLog | 4 ++++
  gdb/inflow.c  | 4 ++--
  2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index e9b0377..b188988 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2015-01-07  Patrick Palka  <patrick@parcs.ath.cx>
+
+	* inflow.c (initial_gdb_ttystate): Tweak comment.
+
  2015-01-07  Joel Brobecker  <brobecker@adacore.com>

  	* inflow.c (set_initial_gdb_ttystate): Add empty line after
diff --git a/gdb/inflow.c b/gdb/inflow.c
index 4c81a68..1456fd8 100644
--- a/gdb/inflow.c
+++ b/gdb/inflow.c
@@ -79,8 +79,8 @@ struct terminal_info
     unimportant.  */
  static struct terminal_info our_terminal_info;

-/* The initial tty state given to each new inferior.  It is a snapshot of our
-   own tty state taken during initialization of GDB.  */
+/* Snapshot of our own tty state taken during initialization of GDB.
+   This is used as the initial tty state given to each new inferior.  */
  static serial_ttystate initial_gdb_ttystate;

  static struct terminal_info *get_inflow_inferior_data (struct inferior *);
-- 
2.2.1.212.gc5b9256