Re: [PATCH] PR cli/21688: Fix multi-line/inline command differentiation

[Sergio Durigan Junior <sergiodj at redhat dot com>]

On Thursday, June 29 2017, Simon Marchi wrote:

> On 2017-06-29 21:48, Sergio Durigan Junior wrote:
>> On Thursday, June 29 2017, Simon Marchi wrote:
>>> Another (maybe simpler) way would be to check
>>>
>>>   else if (command_name_equals (cmd, "python") && *cmd_name == '\0')
>>>
>>> It's not clear when expressed like this though because cmd_name is not
>>> well named at this point (it points just after the command name).
>>
>> Hm, right.  Would you prefer this way instead?  I don't have a strong
>> opinion on this.
>
> My opinion is the solution with the least code is probably best, if
> they are equivalent otherwise, but I don't really mind.  It's just a
> suggestion.

Right.  I did some more tests here, and unfortunately your solution
doesn't work for all cases.  For example, if the user puts trailing
whitespace on the command name (like "python "), *cmd_name will point to
a whitespace after the call to lookup_cmd_1.

So here's second version of the patch, with the fixes you requested
except the one above.  WDYT?

-- 
Sergio
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>From 5c80c97c4a11ec954cc5d426e77cf209dc43f10d Mon Sep 17 00:00:00 2001
From: Sergio Durigan Junior <sergiodj@redhat.com>
Date: Wed, 28 Jun 2017 21:55:03 -0400
Subject: [PATCH] PR cli/21688: Fix multi-line/inline command differentiation

This bug is a regression caused by the following commit:

  604c4576fdcfc4e7c28f569b3748a1b6b4e0dbd4 is the first bad commit
  commit 604c4576fdcfc4e7c28f569b3748a1b6b4e0dbd4
  Author: Jerome Guitton <guitton@adacore.com>
  Date:   Tue Jan 10 15:15:53 2017 +0100

The problem happens because, on cli/cli-script.c:process_next_line,
GDB is not using the command line string to identify which command to
run, but it instead using the 'struct cmd_list_element *' that is
obtained by using the mentioned string.  The problem with that is that
the 'struct cmd_list_element *' doesn't have any information on
whether the command issued by the user is a multi-line or inline one.

A multi-line command is a command that will necessarily be composed of
more than 1 line.  For example:

  (gdb) if 1
  >python
   >print ('hello')
   >end
  >end

As can be seen in the example above, the 'python' command actually
"opens" a new command line (represented by the change in the
indentation) that will then be used to enter Python code.  OTOH, an
inline command is a command that is "self-contained" in a single line,
for example:

  (gdb) if 1
  >python print ('hello')
  >end

This Python command is a one-liner, and therefore there is no other
Python code that can be entered for this same block.  There is also no
change in the indentation.

So, the fix is somewhat simple: we have to revert the change and use
the full command line string passed to process_next_line in order to
identify whether we're dealing with a multi-line or an inline command.
This commit does just that.  As can be seen, this regression also
affects other languages, like guile or the compile framework.  To make
things clearer, I decided to create a new helper function responsible
for identifying a non-inline command.

Testcase is attached.

gdb/ChangeLog:
2017-06-29  Sergio Durigan Junior  <sergiodj@redhat.com>

	PR cli/21688
	* cli/cli-script.c (command_name_equals_not_inline): New function.
	(process_next_line): Adjust 'if' clauses for "python", "compile"
	and "guile" to use command_name_equals_not_inline.

gdb/testsuite/ChangeLog:
2017-06-29  Sergio Durigan Junior  <sergiodj@redhat.com>

	PR cli/21688
	* gdb.python/py-cmd.exp (test_python_inline_or_multiline): New
	procedure.  Call it.
---
 gdb/ChangeLog                       |  7 +++++++
 gdb/cli/cli-script.c                | 21 +++++++++++++++++----
 gdb/testsuite/ChangeLog             |  6 ++++++
 gdb/testsuite/gdb.python/py-cmd.exp | 32 ++++++++++++++++++++++++++++++++
 4 files changed, 62 insertions(+), 4 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index b47226bc..7d0f5cf 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2017-06-29  Sergio Durigan Junior  <sergiodj@redhat.com>
+
+	PR cli/21688
+	* cli/cli-script.c (command_name_equals_not_inline): New function.
+	(process_next_line): Adjust 'if' clauses for "python", "compile"
+	and "guile" to use command_name_equals_not_inline.
+
 2017-06-29  Pedro Alves  <palves@redhat.com>
 
 	* completer.c (expression_completer): Call
diff --git a/gdb/cli/cli-script.c b/gdb/cli/cli-script.c
index e0e27ef..72f316f 100644
--- a/gdb/cli/cli-script.c
+++ b/gdb/cli/cli-script.c
@@ -900,6 +900,20 @@ command_name_equals (struct cmd_list_element *cmd, const char *name)
 	  && strcmp (cmd->name, name) == 0);
 }
 
+/* Return true if NAME is the only command between COMMAND_START and
+   COMMAND_END.  This is useful when we want to know whether the
+   command is inline (i.e., has arguments like 'python command1') or
+   is the start of a multi-line command block.  */
+
+static bool
+command_name_equals_not_inline (const char *command_start,
+				const char *command_end,
+				const char *name)
+{
+  return (command_end - command_start == strlen (name)
+	  && startswith (command_start, name));
+}
+
 /* Given an input line P, skip the command and return a pointer to the
    first argument.  */
 
@@ -997,21 +1011,20 @@ process_next_line (char *p, struct command_line **command, int parse_commands,
 	{
 	  *command = build_command_line (commands_control, line_first_arg (p));
 	}
-      else if (command_name_equals (cmd, "python"))
+      else if (command_name_equals_not_inline (p_start, p_end, "python"))
 	{
 	  /* Note that we ignore the inline "python command" form
 	     here.  */
 	  *command = build_command_line (python_control, "");
 	}
-      else if (command_name_equals (cmd, "compile"))
+      else if (command_name_equals_not_inline (p_start, p_end, "compile"))
 	{
 	  /* Note that we ignore the inline "compile command" form
 	     here.  */
 	  *command = build_command_line (compile_control, "");
 	  (*command)->control_u.compile.scope = COMPILE_I_INVALID_SCOPE;
 	}
-
-      else if (command_name_equals (cmd, "guile"))
+      else if (command_name_equals_not_inline (p_start, p_end, "guile"))
 	{
 	  /* Note that we ignore the inline "guile command" form here.  */
 	  *command = build_command_line (guile_control, "");
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 41c5434..51dd86d 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2017-06-29  Sergio Durigan Junior  <sergiodj@redhat.com>
+
+	PR cli/21688
+	* gdb.python/py-cmd.exp (test_python_inline_or_multiline): New
+	procedure.  Call it.
+
 2017-06-29  Pedro Alves  <palves@redhat.com>
 
 	* gdb.base/printcmds.exp: Add tests.
diff --git a/gdb/testsuite/gdb.python/py-cmd.exp b/gdb/testsuite/gdb.python/py-cmd.exp
index 2dbf23ce..39bb785 100644
--- a/gdb/testsuite/gdb.python/py-cmd.exp
+++ b/gdb/testsuite/gdb.python/py-cmd.exp
@@ -181,6 +181,38 @@ gdb_test "complete expr_test bar\." \
     "expr_test bar\.bc.*expr_test bar\.ij.*" \
     "test completion through complete command"
 
+# Test that the "python" command is correctly recognized as
+# inline/multi-line when entering a sequence of commands.
+#
+# This proc tests PR cli/21688.  The PR is not language-specific, but
+# the easiest way is just to test with Python.
+proc test_python_inline_or_multiline { } {
+    set define_cmd_not_inline {
+	{ "if 1"                 " >$"            "multi-line if 1" }
+	{ "python"               " >$"            "multi-line python command" }
+	{ "print ('hello')"      "  >$"           "multi-line print" }
+	{ "end"                  " >$"            "multi-line first end" }
+	{ "end"                  "hello\r\n"      "multi-line last end" } }
+
+    set define_cmd_inline {
+	{ "if 1"                      " >$"          "inline if 1" }
+	{ "python print ('hello')"    " >$"          "inline python command" }
+	{ "end"                       "hello\r\n"    "inline end" } }
+
+    foreach t [list $define_cmd_not_inline $define_cmd_inline] {
+	foreach l $t {
+	    lassign $l command regex testmsg
+	    gdb_test_multiple "$command" "$testmsg" {
+		-re "$regex" {
+		    pass "$testmsg"
+		}
+	    }
+	}
+    }
+}
+
+test_python_inline_or_multiline
+
 if { [readline_is_used] } {
     set test "complete 'expr_test bar.i'"
     send_gdb "expr_test bar\.i\t\t"
-- 
2.9.3