[PATCH] Make gdb.base/corefile.exp work on terminals with few rows

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[PATCH] Make gdb.base/corefile.exp work on terminals with few rows

Simon Marchi
When creating a pty to spawn a subprocess (such as gdb), Expect
copies the settings of its own controlling terminal, including the
number of rows and columns.  If you "make check" on a terminal with just
a few rows (e.g. 4), GDB will paginate before reaching the initial
prompt.  In default_gdb_start, used by most tests, this is already
handled: if we see the pagination prompt, we sent \n to continue.

Philippe reported that gdb.base/corefile.exp didn't work in terminals
with just a few rows.  This test spawns GDB by hand, because it needs to
check things before the initial prompt, which it couldn't do if it used
default_gdb_start.

In this case I think it's not safe to use the same technique as in
default_gdb_start.  Even if we could send a \n if we see a pagination
prompt, we match some multiline regexes in there.  So if a pagination
slips in there, it might make the regexes not match and fail the test.

It's also not possible to use -ex "set height 0" or -iex "set height 0",
it is handled after the introduction text is shown.

The simplest way I found to avoid showing the pagination completely is
to set stty_init (documented in expect's man page) to initialize gdb's
pty with a fixed number of rows.

gdb/testsuite/ChangeLog:

        * gdb.base/corefile.exp: Set stty_init.
---
 gdb/testsuite/gdb.base/corefile.exp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/gdb/testsuite/gdb.base/corefile.exp b/gdb/testsuite/gdb.base/corefile.exp
index 0053f0594586..c494a875bd31 100644
--- a/gdb/testsuite/gdb.base/corefile.exp
+++ b/gdb/testsuite/gdb.base/corefile.exp
@@ -39,6 +39,10 @@ if {$corefile == ""} {
     return 0
 }
 
+# Initialize GDB's pty with a fixed size, to make sure we avoid pagination
+# during startup.  See "man expect" for details about stty_init.
+set stty_init "rows 25 cols 80"
+
 # Test that we can simply startup with a "-core=$corefile" command line arg
 # and recognize that the core file is a valid, usable core file.
 # To do this, we must shutdown the currently running gdb and restart
--
2.20.1

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Re: [PATCH] Make gdb.base/corefile.exp work on terminals with few rows

Pedro Alves-7
On 02/06/2019 03:48 AM, Simon Marchi wrote:

> When creating a pty to spawn a subprocess (such as gdb), Expect
> copies the settings of its own controlling terminal, including the
> number of rows and columns.  If you "make check" on a terminal with just
> a few rows (e.g. 4), GDB will paginate before reaching the initial
> prompt.  In default_gdb_start, used by most tests, this is already
> handled: if we see the pagination prompt, we sent \n to continue.
>
> Philippe reported that gdb.base/corefile.exp didn't work in terminals
> with just a few rows.  This test spawns GDB by hand, because it needs to
> check things before the initial prompt, which it couldn't do if it used
> default_gdb_start.
>
> In this case I think it's not safe to use the same technique as in
> default_gdb_start.  Even if we could send a \n if we see a pagination
> prompt, we match some multiline regexes in there.  So if a pagination
> slips in there, it might make the regexes not match and fail the test.
>
> It's also not possible to use -ex "set height 0" or -iex "set height 0",
> it is handled after the introduction text is shown.
>
> The simplest way I found to avoid showing the pagination completely is
> to set stty_init (documented in expect's man page) to initialize gdb's
> pty with a fixed number of rows.

Hmm, good idea.  But, if you have a small terminal with just a few
columns (as opposed to rows), then the testsuite all breaks, AFAICT.

E.g., I just tried running gdb.base/break.exp with a small window and
the test hangs starting GDB.

But with:

 --- c/gdb/testsuite/lib/gdb.exp
 +++ w/gdb/testsuite/lib/gdb.exp
 @@ -4752,6 +4752,9 @@ proc gdb_init { test_file_name } {
      # tests.
      setenv TERM "dumb"
 
 +    global stty_init
 +    set stty_init "rows 25 cols 80"
 +
      # Some tests (for example gdb.base/maint.exp) shell out from gdb to use
      # grep.  Clear GREP_OPTIONS to make the behavior predictable,
      # especially having color output turned on can cause tests to fail.

... it passes.  And so does gdb.base/corefile.exp.

Is there any reason we'd ever want GDB's terminal size to match
whatever the user's term size was?  I'd think that sanitizing / forcing
the same sizes everywhere would just lead to more stable testing,
and thus be a good thing.

Thanks,
Pedro Alves
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Re: [PATCH] Make gdb.base/corefile.exp work on terminals with few rows

Simon Marchi-2
On 2019-02-06 1:42 p.m., Pedro Alves wrote:

> On 02/06/2019 03:48 AM, Simon Marchi wrote:
>> When creating a pty to spawn a subprocess (such as gdb), Expect
>> copies the settings of its own controlling terminal, including the
>> number of rows and columns.  If you "make check" on a terminal with just
>> a few rows (e.g. 4), GDB will paginate before reaching the initial
>> prompt.  In default_gdb_start, used by most tests, this is already
>> handled: if we see the pagination prompt, we sent \n to continue.
>>
>> Philippe reported that gdb.base/corefile.exp didn't work in terminals
>> with just a few rows.  This test spawns GDB by hand, because it needs to
>> check things before the initial prompt, which it couldn't do if it used
>> default_gdb_start.
>>
>> In this case I think it's not safe to use the same technique as in
>> default_gdb_start.  Even if we could send a \n if we see a pagination
>> prompt, we match some multiline regexes in there.  So if a pagination
>> slips in there, it might make the regexes not match and fail the test.
>>
>> It's also not possible to use -ex "set height 0" or -iex "set height 0",
>> it is handled after the introduction text is shown.
>>
>> The simplest way I found to avoid showing the pagination completely is
>> to set stty_init (documented in expect's man page) to initialize gdb's
>> pty with a fixed number of rows.
>
> Hmm, good idea.  But, if you have a small terminal with just a few
> columns (as opposed to rows), then the testsuite all breaks, AFAICT.
>
> E.g., I just tried running gdb.base/break.exp with a small window and
> the test hangs starting GDB.
>
> But with:
>
>  --- c/gdb/testsuite/lib/gdb.exp
>  +++ w/gdb/testsuite/lib/gdb.exp
>  @@ -4752,6 +4752,9 @@ proc gdb_init { test_file_name } {
>       # tests.
>       setenv TERM "dumb"
>  
>  +    global stty_init
>  +    set stty_init "rows 25 cols 80"
>  +
>       # Some tests (for example gdb.base/maint.exp) shell out from gdb to use
>       # grep.  Clear GREP_OPTIONS to make the behavior predictable,
>       # especially having color output turned on can cause tests to fail.
>
> ... it passes.  And so does gdb.base/corefile.exp.
>
> Is there any reason we'd ever want GDB's terminal size to match
> whatever the user's term size was?  I'd think that sanitizing / forcing
> the same sizes everywhere would just lead to more stable testing,
> and thus be a good thing.

Agreed.  If we do this, we can remove the part where we match the pagination
prompt during startup, like so:


From 67bb1dde957fcd8a0168fb04afa3f8e3a4ccf9bb Mon Sep 17 00:00:00 2001
From: Simon Marchi <[hidden email]>
Date: Tue, 5 Feb 2019 22:48:57 -0500
Subject: [PATCH] Make gdb.base/corefile.exp work on terminals with few rows

When creating a pty to spawn a subprocess (such as gdb), Expect
copies the settings of its own controlling terminal, including the
number of rows and columns.  If you "make check" on a terminal with just
a few rows (e.g. 4), GDB will paginate before reaching the initial
prompt.  In default_gdb_start, used by most tests, this is already
handled: if we see the pagination prompt, we sent \n to continue.

Philippe reported that gdb.base/corefile.exp didn't work in terminals
with just a few rows.  This test spawns GDB by hand, because it needs to
check things before the initial prompt, which it couldn't do if it used
default_gdb_start.

In this case I think it's not safe to use the same technique as in
default_gdb_start.  Even if we could send a \n if we see a pagination
prompt, we match some multiline regexes in there.  So if a pagination
slips in there, it might make the regexes not match and fail the test.

It's also not possible to use -ex "set height 0" or -iex "set height 0",
it is handled after the introduction text is shown.

The simplest way I found to avoid showing the pagination completely is
to set stty_init (documented in expect's man page) to initialize gdb's
pty with a fixed number of rows.

And actually, if we set stty_init in gdb_init, it works nicely as a
general solution applicable to all tests.  We can therefore remove the
solution introduced in e882ef3cfc3 ("testsuite: expect possible
pagination when starting gdb") where we matched the pagination prompt
during startup.

gdb/testsuite/ChangeLog:

        * lib/gdb.exp (default_gdb_start): Don't match pagination
        prompt.
        (gdb_init): Set stty_init.
---
 gdb/testsuite/lib/gdb.exp | 44 ++++++++++++++++++---------------------
 1 file changed, 20 insertions(+), 24 deletions(-)

diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index bc7ba12d480..d05854329d8 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -1638,7 +1638,7 @@ proc default_gdb_spawn { } {
 # Default gdb_start procedure.

 proc default_gdb_start { } {
-    global gdb_prompt pagination_prompt
+    global gdb_prompt
     global gdb_spawn_id
     global inferior_spawn_id

@@ -1659,29 +1659,20 @@ proc default_gdb_start { } {
     # When running over NFS, particularly if running many simultaneous
     # tests on different hosts all using the same server, things can
     # get really slow.  Give gdb at least 3 minutes to start up.
-    set loop_again 1
-    while { $loop_again } {
- set loop_again 0
- gdb_expect 360 {
-    -re "$pagination_prompt" {
- verbose "Hit pagination during startup. Pressing enter to continue."
- send_gdb "\n"
- set loop_again 1
-    }
-    -re "\[\r\n\]$gdb_prompt $" {
- verbose "GDB initialized."
-    }
-    -re "$gdb_prompt $" {
- perror "GDB never initialized."
- unset gdb_spawn_id
- return -1
-    }
-    timeout {
- perror "(timeout) GDB never initialized after 10 seconds."
- remote_close host
- unset gdb_spawn_id
- return -1
-    }
+    gdb_expect 360 {
+ -re "\[\r\n\]$gdb_prompt $" {
+    verbose "GDB initialized."
+ }
+ -re "$gdb_prompt $" {
+    perror "GDB never initialized."
+    unset gdb_spawn_id
+    return -1
+ }
+ timeout {
+    perror "(timeout) GDB never initialized after 10 seconds."
+    remote_close host
+    unset gdb_spawn_id
+    return -1
  }
     }

@@ -4752,6 +4743,11 @@ proc gdb_init { test_file_name } {
     # tests.
     setenv TERM "dumb"

+    # Initialize GDB's pty with a fixed size, to make sure we avoid pagination
+    # during startup.  See "man expect" for details about stty_init.
+    global stty_init
+    set stty_init "rows 25 cols 80"
+
     # Some tests (for example gdb.base/maint.exp) shell out from gdb to use
     # grep.  Clear GREP_OPTIONS to make the behavior predictable,
     # especially having color output turned on can cause tests to fail.
--
2.20.1

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Re: [PATCH] Make gdb.base/corefile.exp work on terminals with few rows

Pedro Alves-7
On 02/06/2019 11:11 PM, Simon Marchi wrote:

> Agreed.  If we do this, we can remove the part where we match the pagination
> prompt during startup, like so:

LGTM.

Thanks,
Pedro Alves
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Re: [PATCH] Make gdb.base/corefile.exp work on terminals with few rows

Simon Marchi
On 2019-02-07 08:26, Pedro Alves wrote:

> On 02/06/2019 11:11 PM, Simon Marchi wrote:
>
>> Agreed.  If we do this, we can remove the part where we match the
>> pagination
>> prompt during startup, like so:
>
> LGTM.
>
> Thanks,
> Pedro Alves

Thanks, pushed.

Simon