[gdb/testsuite] Don't leak tuiterm.exp spawn override

In lib/tuiterm.exp the builtin spawn is overridden by a tui-specific version.

After running the first test-case that imports tuiterm.exp, the override
remains active, so it can cause trouble in subsequent test-cases, even if they
do not import tuiterm.exp.  See f.i. commit c8d4f6dfd9 "[gdb/testsuite] Fix
spawn in tuiterm.exp".

Fix this by:
- adding a variable gdb_finish_hooks which is a list of procs to run during
  gdb_finish
- adding a proc tuiterm_env that is used in test-cases instead of
  "load_lib tuiterm.exp".
- letting tuiterm_env:
  - install the tui-specific spawn version, and
  - use the gdb_finish_hooks to schedule restoring the builtin spawn
    version.

Tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2020-06-05  Tom de Vries  <tdevries@suse.de>

	* lib/tuiterm.exp (spawn): Rename to ...
	(tui_spawn): ... this.
	(toplevel): Move rename of spawn ...
	(gdb_init_tuiterm): ... here.  New proc.
	(gdb_finish_tuiterm): New proc.
	* lib/gdb.exp (gdb_finish_hooks): New global var.
	(gdb_finish): Handle gdb_finish_hooks.
	(tuiterm_env): New proc.
	* gdb.python/tui-window.exp: Replace load_lib tuiterm.exp with
	tuiterm_env.
	* gdb.tui/basic.exp: Same.
	* gdb.tui/corefile-run.exp: Same.
	* gdb.tui/empty.exp: Same.
	* gdb.tui/list-before.exp: Same.
	* gdb.tui/list.exp: Same.
	* gdb.tui/main.exp: Same.
	* gdb.tui/new-layout.exp: Same.
	* gdb.tui/regs.exp: Same.
	* gdb.tui/resize.exp: Same.
	* gdb.tui/tui-layout-asm-short-prog.exp: Same.
	* gdb.tui/tui-layout-asm.exp: Same.
	* gdb.tui/tui-missing-src.exp: Same.
	* gdb.tui/winheight.exp: Same.

---
 gdb/testsuite/gdb.python/tui-window.exp            |  2 +-
 gdb/testsuite/gdb.tui/basic.exp                    |  2 +-
 gdb/testsuite/gdb.tui/corefile-run.exp             |  2 +-
 gdb/testsuite/gdb.tui/empty.exp                    |  2 +-
 gdb/testsuite/gdb.tui/list-before.exp              |  2 +-
 gdb/testsuite/gdb.tui/list.exp                     |  2 +-
 gdb/testsuite/gdb.tui/main.exp                     |  2 +-
 gdb/testsuite/gdb.tui/new-layout.exp               |  2 +-
 gdb/testsuite/gdb.tui/regs.exp                     |  2 +-
 gdb/testsuite/gdb.tui/resize.exp                   |  2 +-
 .../gdb.tui/tui-layout-asm-short-prog.exp          |  2 +-
 gdb/testsuite/gdb.tui/tui-layout-asm.exp           |  2 +-
 gdb/testsuite/gdb.tui/tui-missing-src.exp          |  2 +-
 gdb/testsuite/gdb.tui/winheight.exp                |  2 +-
 gdb/testsuite/lib/gdb.exp                          | 23 ++++++++++++++++++++++
 gdb/testsuite/lib/tuiterm.exp                      | 17 ++++++++++++++--
 16 files changed, 52 insertions(+), 16 deletions(-)

diff --git a/gdb/testsuite/gdb.python/tui-window.exp b/gdb/testsuite/gdb.python/tui-window.exp
index 1a4feebe22..503823a229 100644
--- a/gdb/testsuite/gdb.python/tui-window.exp
+++ b/gdb/testsuite/gdb.python/tui-window.exp
@@ -16,7 +16,7 @@
 # Test a TUI window implemented in Python.
 
 load_lib gdb-python.exp
-load_lib tuiterm.exp
+tuiterm_env
 
 # This test doesn't care about the inferior.
 standard_testfile py-arch.c
diff --git a/gdb/testsuite/gdb.tui/basic.exp b/gdb/testsuite/gdb.tui/basic.exp
index 34e60384c4..3e013a9515 100644
--- a/gdb/testsuite/gdb.tui/basic.exp
+++ b/gdb/testsuite/gdb.tui/basic.exp
@@ -15,7 +15,7 @@
 
 # Basic TUI tests.
 
-load_lib "tuiterm.exp"
+tuiterm_env
 
 standard_testfile tui-layout.c
 
diff --git a/gdb/testsuite/gdb.tui/corefile-run.exp b/gdb/testsuite/gdb.tui/corefile-run.exp
index 440142f74e..1878770bdc 100644
--- a/gdb/testsuite/gdb.tui/corefile-run.exp
+++ b/gdb/testsuite/gdb.tui/corefile-run.exp
@@ -18,7 +18,7 @@
 #
 # Ref.: https://bugzilla.redhat.com/show_bug.cgi?id=1765117
 
-load_lib "tuiterm.exp"
+tuiterm_env
 
 standard_testfile tui-layout.c
 
diff --git a/gdb/testsuite/gdb.tui/empty.exp b/gdb/testsuite/gdb.tui/empty.exp
index e5d0228062..89f49d6b7f 100644
--- a/gdb/testsuite/gdb.tui/empty.exp
+++ b/gdb/testsuite/gdb.tui/empty.exp
@@ -15,7 +15,7 @@
 
 # Test TUI resizing with empty windows.
 
-load_lib "tuiterm.exp"
+tuiterm_env
 
 standard_testfile
 
diff --git a/gdb/testsuite/gdb.tui/list-before.exp b/gdb/testsuite/gdb.tui/list-before.exp
index d2f3ef472d..9c5eb5655e 100644
--- a/gdb/testsuite/gdb.tui/list-before.exp
+++ b/gdb/testsuite/gdb.tui/list-before.exp
@@ -15,7 +15,7 @@
 
 # Ensure that "list" before starting the TUI will affect the view.
 
-load_lib "tuiterm.exp"
+tuiterm_env
 
 standard_testfile tui-layout.c
 
diff --git a/gdb/testsuite/gdb.tui/list.exp b/gdb/testsuite/gdb.tui/list.exp
index 41cec125d5..b1e59499c8 100644
--- a/gdb/testsuite/gdb.tui/list.exp
+++ b/gdb/testsuite/gdb.tui/list.exp
@@ -15,7 +15,7 @@
 
 # Ensure that "list" will switch to the source view.
 
-load_lib "tuiterm.exp"
+tuiterm_env
 
 standard_testfile tui-layout.c
 
diff --git a/gdb/testsuite/gdb.tui/main.exp b/gdb/testsuite/gdb.tui/main.exp
index ae2393e6e9..fd3c2cd815 100644
--- a/gdb/testsuite/gdb.tui/main.exp
+++ b/gdb/testsuite/gdb.tui/main.exp
@@ -15,7 +15,7 @@
 
 # Test that "file" shows "main".
 
-load_lib "tuiterm.exp"
+tuiterm_env
 
 standard_testfile tui-layout.c
 
diff --git a/gdb/testsuite/gdb.tui/new-layout.exp b/gdb/testsuite/gdb.tui/new-layout.exp
index b71de7de5f..3ea4dd4069 100644
--- a/gdb/testsuite/gdb.tui/new-layout.exp
+++ b/gdb/testsuite/gdb.tui/new-layout.exp
@@ -15,7 +15,7 @@
 
 # Test "tui new-layout".
 
-load_lib "tuiterm.exp"
+tuiterm_env
 
 standard_testfile tui-layout.c
 
diff --git a/gdb/testsuite/gdb.tui/regs.exp b/gdb/testsuite/gdb.tui/regs.exp
index e31a47d47b..a9296a7d5f 100644
--- a/gdb/testsuite/gdb.tui/regs.exp
+++ b/gdb/testsuite/gdb.tui/regs.exp
@@ -15,7 +15,7 @@
 
 # Simple test of TUI register window.
 
-load_lib "tuiterm.exp"
+tuiterm_env
 
 standard_testfile tui-layout.c
 
diff --git a/gdb/testsuite/gdb.tui/resize.exp b/gdb/testsuite/gdb.tui/resize.exp
index 1b3f407a02..fd1b35088a 100644
--- a/gdb/testsuite/gdb.tui/resize.exp
+++ b/gdb/testsuite/gdb.tui/resize.exp
@@ -15,7 +15,7 @@
 
 # Test TUI resizing.
 
-load_lib "tuiterm.exp"
+tuiterm_env
 
 standard_testfile tui-layout.c
 
diff --git a/gdb/testsuite/gdb.tui/tui-layout-asm-short-prog.exp b/gdb/testsuite/gdb.tui/tui-layout-asm-short-prog.exp
index 4aa1ba3046..50cb61f0fa 100644
--- a/gdb/testsuite/gdb.tui/tui-layout-asm-short-prog.exp
+++ b/gdb/testsuite/gdb.tui/tui-layout-asm-short-prog.exp
@@ -16,7 +16,7 @@
 # Ensure that 'layout asm' can scroll away from the last line of a
 # very short program using a page up sized scroll.
 
-load_lib "tuiterm.exp"
+tuiterm_env
 
 standard_testfile tui-layout-asm-short-prog.S
 
diff --git a/gdb/testsuite/gdb.tui/tui-layout-asm.exp b/gdb/testsuite/gdb.tui/tui-layout-asm.exp
index 257321fec7..44f7a3a3a4 100644
--- a/gdb/testsuite/gdb.tui/tui-layout-asm.exp
+++ b/gdb/testsuite/gdb.tui/tui-layout-asm.exp
@@ -16,7 +16,7 @@
 # Ensure that 'layout asm' before starting the inferior puts us in the
 # asm layout and displays the disassembly for main.
 
-load_lib "tuiterm.exp"
+tuiterm_env
 
 standard_testfile tui-layout.c
 
diff --git a/gdb/testsuite/gdb.tui/tui-missing-src.exp b/gdb/testsuite/gdb.tui/tui-missing-src.exp
index 2d9a851bec..6b5c7fad4c 100644
--- a/gdb/testsuite/gdb.tui/tui-missing-src.exp
+++ b/gdb/testsuite/gdb.tui/tui-missing-src.exp
@@ -25,7 +25,7 @@
 #    layout must show the contents of f2.c.
 # 7. Going back to main() shall result in no contents again.
 
-load_lib "tuiterm.exp"
+tuiterm_env
 
 standard_testfile
 
diff --git a/gdb/testsuite/gdb.tui/winheight.exp b/gdb/testsuite/gdb.tui/winheight.exp
index 7a17c311ea..8ac55f8472 100644
--- a/gdb/testsuite/gdb.tui/winheight.exp
+++ b/gdb/testsuite/gdb.tui/winheight.exp
@@ -15,7 +15,7 @@
 
 # Test the "winheight" command.
 
-load_lib "tuiterm.exp"
+tuiterm_env
 
 standard_testfile tui-layout.c
 
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 64e667c20e..e7fce6fee0 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -25,6 +25,9 @@ if {$tool == ""} {
     exit 2
 }
 
+# List of procs to run in gdb_finish.
+set gdb_finish_hooks [list]
+
 load_lib libgloss.exp
 load_lib cache.exp
 load_lib gdb-utils.exp
@@ -5241,6 +5244,12 @@ proc gdb_finish { } {
 	}
 	set banned_traced 0
     }
+
+    global gdb_finish_hooks
+    foreach gdb_finish_hook $gdb_finish_hooks {
+	$gdb_finish_hook
+    }
+    set gdb_finish_hooks [list]
 }
 
 global debug_format
@@ -7259,5 +7268,19 @@ proc with_override { name override body } {
     return $result
 }
 
+# Setup tuiterm.exp environment.  To be used in test-cases instead of
+# "load_lib tuiterm.exp".  Calls initialization function and schedules
+# finalization function.
+proc tuiterm_env { } {
+    load_lib tuiterm.exp
+
+    # Do initialization.
+    tuiterm_env_init
+
+    # Schedule finalization.
+    global gdb_finish_hooks
+    lappend gdb_finish_hooks tuiterm_env_finish
+}
+
 # Always load compatibility stuff.
 load_lib future.exp
diff --git a/gdb/testsuite/lib/tuiterm.exp b/gdb/testsuite/lib/tuiterm.exp
index 8c9f97af6e..44cbc79730 100644
--- a/gdb/testsuite/lib/tuiterm.exp
+++ b/gdb/testsuite/lib/tuiterm.exp
@@ -19,8 +19,7 @@
 # array; but dejagnu doesn't export this globally.  So, we have to
 # wrap spawn with our own function, so that we can capture this value.
 # The value is later used in calls to stty.
-rename spawn builtin_spawn
-proc spawn {args} {
+proc tuiterm_spawn { args } {
     set result [uplevel builtin_spawn $args]
     global gdb_spawn_name
     upvar spawn_out spawn_out
@@ -32,6 +31,20 @@ proc spawn {args} {
     return $result
 }
 
+# Initialize tuiterm.exp environment.
+proc tuiterm_env_init { } {
+    # Override spawn with tui_spawn.
+    rename spawn builtin_spawn
+    rename tuiterm_spawn spawn
+}
+
+# Finalize tuiterm.exp environment.
+proc tuiterm_env_finish { } {
+    # Restore spawn.
+    rename spawn tuiterm_spawn
+    rename builtin_spawn spawn
+}
+
 namespace eval Term {
     variable _rows
     variable _cols