boolean/auto-boolean commands, make "o" ambiguous

We currently accept "o" with boolean/auto-boolean commands, taking it
to mean "on".  But "o" is ambiguous, between "on" and "off".  I can't
imagine why assuming the user wanted to type "on" is a good idea, it
might have been a typo.

This commit makes gdb error out.  We now get:

 (gdb) maint test-settings set boolean o
 "on" or "off" expected.

 (gdb) maint test-settings set auto-boolean o
 "on", "off" or "auto" expected.

gdb/ChangeLog:
2019-06-13  Pedro Alves  <palves@redhat.com>

	* cli/cli-setshow.c (parse_auto_binary_operation)
	(parse_cli_boolean_value): Don't allow "o".

gdb/testsuite/ChangeLog:
2019-06-13  Pedro Alves  <palves@redhat.com>

	* gdb.base/settings.exp (test-boolean, test-auto-boolean): Check
	that "o" is ambiguous.

4 files changed, 28 insertions, 7 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 1828a74..63a3690 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,10 @@
 2019-06-13  Pedro Alves  <palves@redhat.com>
 
+	* cli/cli-setshow.c (parse_auto_binary_operation)
+	(parse_cli_boolean_value): Don't allow "o".
+
+2019-06-13  Pedro Alves  <palves@redhat.com>
+
 	* Makefile.in (COMMON_SFILES): Add maint-test-settings.c.
 	* NEWS: Mention maint test-settings KIND.
 	* maint-test-settings.c: New file.
diff --git a/gdb/cli/cli-setshow.c b/gdb/cli/cli-setshow.c
index 86ebed4..9841ec1 100644
--- a/gdb/cli/cli-setshow.c
+++ b/gdb/cli/cli-setshow.c
@@ -54,18 +54,21 @@ parse_auto_binary_operation (const char *arg)
 
       while (isspace (arg[length - 1]) && length > 0)
 	length--;
-      if (strncmp (arg, "on", length) == 0
+
+      /* Note that "o" is ambiguous.  */
+
+      if ((length == 2 && strncmp (arg, "on", length) == 0)
 	  || strncmp (arg, "1", length) == 0
 	  || strncmp (arg, "yes", length) == 0
 	  || strncmp (arg, "enable", length) == 0)
 	return AUTO_BOOLEAN_TRUE;
-      else if (strncmp (arg, "off", length) == 0
+      else if ((length >= 2 && strncmp (arg, "off", length) == 0)
 	       || strncmp (arg, "0", length) == 0
 	       || strncmp (arg, "no", length) == 0
 	       || strncmp (arg, "disable", length) == 0)
 	return AUTO_BOOLEAN_FALSE;
       else if (strncmp (arg, "auto", length) == 0
-	       || (strncmp (arg, "-1", length) == 0 && length > 1))
+	       || (length > 1 && strncmp (arg, "-1", length) == 0))
 	return AUTO_BOOLEAN_AUTO;
     }
   error (_("\"on\", \"off\" or \"auto\" expected."));
@@ -87,12 +90,14 @@ parse_cli_boolean_value (const char *arg)
   while (arg[length - 1] == ' ' || arg[length - 1] == '\t')
     length--;
 
-  if (strncmp (arg, "on", length) == 0
+  /* Note that "o" is ambiguous.  */
+
+  if ((length == 2 && strncmp (arg, "on", length) == 0)
       || strncmp (arg, "1", length) == 0
       || strncmp (arg, "yes", length) == 0
       || strncmp (arg, "enable", length) == 0)
     return 1;
-  else if (strncmp (arg, "off", length) == 0
+  else if ((length >= 2 && strncmp (arg, "off", length) == 0)
 	   || strncmp (arg, "0", length) == 0
 	   || strncmp (arg, "no", length) == 0
 	   || strncmp (arg, "disable", length) == 0)
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 85fa7e0..1c362f7 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,10 @@
 2019-06-13  Pedro Alves  <palves@redhat.com>
 
+	* gdb.base/settings.exp (test-boolean, test-auto-boolean): Check
+	that "o" is ambiguous.
+
+2019-06-13  Pedro Alves  <palves@redhat.com>
+
 	* gdb.base/settings.c: New file.
 	* gdb.base/settings.exp: New file.
 
diff --git a/gdb/testsuite/gdb.base/settings.exp b/gdb/testsuite/gdb.base/settings.exp
index f96e9f6..4a7319d 100644
--- a/gdb/testsuite/gdb.base/settings.exp
+++ b/gdb/testsuite/gdb.base/settings.exp
@@ -194,13 +194,16 @@ proc_with_prefix test-boolean {} {
     gdb_test "$set_cmd auto" \
 	"\"on\" or \"off\" expected\\."
 
+    # "o" is ambiguous.
+    gdb_test "$set_cmd o" \
+	"\"on\" or \"off\" expected\\."
+
     # Various valid values.  Test both full value names and
     # abbreviations.
 
     # Note that unlike with auto-bool, empty value implies "on".
     foreach_with_prefix value {
 	""
-	"o"
 	"on"
 	"1"
 	"y"
@@ -278,11 +281,14 @@ proc_with_prefix test-auto-boolean {} {
     gdb_test "$set_cmd on 1" \
 	"\"on\", \"off\" or \"auto\" expected\\."
 
+    # "o" is ambiguous.
+    gdb_test "$set_cmd o" \
+	"\"on\", \"off\" or \"auto\" expected\\."
+
     # Various valid values.  Test both full value names and
     # abbreviations.
 
     foreach_with_prefix value {
-	"o"
 	"on"
 	"1"
 	"y"