Fix regression: expression completer and scope operator (PR gdb/22584)

I noticed this regression in the expression completer:

 "(gdb) p std::[TAB]" => "(gdb) p std::std::"

obviously we should have not completed to "std::std::".

The problem is that in the earlier big completer rework, I missed
taking into account the fact that with expressions, the completion
word point is not always at the start of the symbol name (it is with
linespecs).

The fix is to run the common prefix / LCD string (what readline uses
to expand the input line) through make_completion_match_str too.

New testcase included, exercising both TAB completion and the complete
command.

gdb/ChangeLog:
2017-12-13  Pedro Alves  <palves@redhat.com>

	* completer.c (completion_tracker::maybe_add_completion): New
	'text' and 'word' parameters.  Use make_completion_match_str.
	(completion_tracker::add_completion): New 'text' and 'word'
	parameters.  Pass down.
	(completion_tracker::recompute_lowest_common_denominator): Change
	parameter type to gdb::unique_xmalloc_ptr rval ref.  Adjust.
	* completer.h (completion_tracker::add_completion): New 'text' and
	'word' parameters.
	(completion_tracker::recompute_lowest_common_denominator): Change
	parameter type to gdb::unique_xmalloc_ptr rval ref.
	(completion_tracker::recompute_lowest_common_denominator): Change
	parameter type to gdb::unique_xmalloc_ptr rval ref.
	* symtab.c (completion_list_add_name): Pass down 'text' and 'word'
	as well.

gdb/testsuite/ChangeLog:
2017-12-13  Pedro Alves  <palves@redhat.com>

	* gdb.cp/cpcompletion.exp: Load completion-support.exp.
	("expression with namespace"): New set of tests.
	* gdb.cp/pr9594.cc (Test_NS::foo, Test_NS::bar)
	(Nested::Test_NS::qux): New.
	* lib/completion-support.exp (test_gdb_complete_cmd_multiple): Add
	defaults to 'start_quote_char' and 'end_quote_char' parameters.

8 files changed, 104 insertions, 13 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 25ef530a101..114a6212121 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,22 @@
 2017-12-13  Pedro Alves  <palves@redhat.com>
 
+	* completer.c (completion_tracker::maybe_add_completion): New
+	'text' and 'word' parameters.  Use make_completion_match_str.
+	(completion_tracker::add_completion): New 'text' and 'word'
+	parameters.  Pass down.
+	(completion_tracker::recompute_lowest_common_denominator): Change
+	parameter type to gdb::unique_xmalloc_ptr rval ref.  Adjust.
+	* completer.h (completion_tracker::add_completion): New 'text' and
+	'word' parameters.
+	(completion_tracker::recompute_lowest_common_denominator): Change
+	parameter type to gdb::unique_xmalloc_ptr rval ref.
+	(completion_tracker::recompute_lowest_common_denominator): Change
+	parameter type to gdb::unique_xmalloc_ptr rval ref.
+	* symtab.c (completion_list_add_name): Pass down 'text' and 'word'
+	as well.
+
+2017-12-13  Pedro Alves  <palves@redhat.com>
+
 	* cli/cli-decode.c (complete_on_cmdlist, complete_on_enum): Use
 	make_completion_match_str.
 	* completer.c: Use gdb::unique_xmalloc_ptr and
diff --git a/gdb/completer.c b/gdb/completer.c
index 01951144867..844696fa03f 100644
--- a/gdb/completer.c
+++ b/gdb/completer.c
@@ -1510,7 +1510,8 @@ completion_tracker::~completion_tracker ()
 bool
 completion_tracker::maybe_add_completion
   (gdb::unique_xmalloc_ptr<char> name,
-   completion_match_for_lcd *match_for_lcd)
+   completion_match_for_lcd *match_for_lcd,
+   const char *text, const char *word)
 {
   void **slot;
 
@@ -1531,7 +1532,10 @@ completion_tracker::maybe_add_completion
       if (match_for_lcd_str == NULL)
 	match_for_lcd_str = name.get ();
 
-      recompute_lowest_common_denominator (match_for_lcd_str);
+      gdb::unique_xmalloc_ptr<char> lcd
+	= make_completion_match_str (match_for_lcd_str, text, word);
+
+      recompute_lowest_common_denominator (std::move (lcd));
 
       *slot = name.get ();
       m_entries_vec.push_back (std::move (name));
@@ -1544,9 +1548,10 @@ completion_tracker::maybe_add_completion
 
 void
 completion_tracker::add_completion (gdb::unique_xmalloc_ptr<char> name,
-				    completion_match_for_lcd *match_for_lcd)
+				    completion_match_for_lcd *match_for_lcd,
+				    const char *text, const char *word)
 {
-  if (!maybe_add_completion (std::move (name), match_for_lcd))
+  if (!maybe_add_completion (std::move (name), match_for_lcd, text, word))
     throw_error (MAX_COMPLETIONS_REACHED_ERROR, _("Max completions reached."));
 }
 
@@ -1904,21 +1909,23 @@ completion_find_completion_word (completion_tracker &tracker, const char *text,
 /* See completer.h.  */
 
 void
-completion_tracker::recompute_lowest_common_denominator (const char *new_match)
+completion_tracker::recompute_lowest_common_denominator
+  (gdb::unique_xmalloc_ptr<char> &&new_match_up)
 {
   if (m_lowest_common_denominator == NULL)
     {
       /* We don't have a lowest common denominator yet, so simply take
-	 the whole NEW_MATCH as being it.  */
-      m_lowest_common_denominator = xstrdup (new_match);
+	 the whole NEW_MATCH_UP as being it.  */
+      m_lowest_common_denominator = new_match_up.release ();
       m_lowest_common_denominator_unique = true;
     }
   else
     {
       /* Find the common denominator between the currently-known
-	 lowest common denominator and NEW_MATCH.  That becomes the
+	 lowest common denominator and NEW_MATCH_UP.  That becomes the
 	 new lowest common denominator.  */
       size_t i;
+      const char *new_match = new_match_up.get ();
 
       for (i = 0;
 	   (new_match[i] != '\0'
diff --git a/gdb/completer.h b/gdb/completer.h
index 73c0f4c7832..df3c8e86de0 100644
--- a/gdb/completer.h
+++ b/gdb/completer.h
@@ -319,7 +319,8 @@ public:
      it is not there already.  If too many completions were already
      found, this throws an error.  */
   void add_completion (gdb::unique_xmalloc_ptr<char> name,
-		       completion_match_for_lcd *match_for_lcd = NULL);
+		       completion_match_for_lcd *match_for_lcd = NULL,
+		       const char *text = NULL, const char *word = NULL);
 
   /* Add all completions matches in LIST.  Elements are moved out of
      LIST.  */
@@ -406,7 +407,8 @@ private:
      it is not there already.  If false is returned, too many
      completions were found.  */
   bool maybe_add_completion (gdb::unique_xmalloc_ptr<char> name,
-			     completion_match_for_lcd *match_for_lcd);
+			     completion_match_for_lcd *match_for_lcd,
+			     const char *text, const char *word);
 
   /* Given a new match, recompute the lowest common denominator (LCD)
      to hand over to readline.  Normally readline computes this itself
@@ -418,7 +420,8 @@ private:
      "std::vector<..>::push_back", "std::string::push_back", etc., and
      in this case we want the lowest common denominator to be
      "push_back" instead of "std::".  */
-  void recompute_lowest_common_denominator (const char *new_match);
+  void recompute_lowest_common_denominator
+    (gdb::unique_xmalloc_ptr<char> &&new_match);
 
   /* Completion match outputs returned by the symbol name matching
      routines (see symbol_name_matcher_ftype).  These results are only
diff --git a/gdb/symtab.c b/gdb/symtab.c
index bb98619a7cb..220ae0969bc 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -4735,7 +4735,7 @@ completion_list_add_name (completion_tracker &tracker,
        in this case we want the completion lowest common denominator
        to be "push_back" instead of "std::".  */
     tracker.add_completion (std::move (completion),
-			    &match_res.match_for_lcd);
+			    &match_res.match_for_lcd, text, word);
   }
 }
 
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index c4d8ecf35b6..450ca3574fb 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,12 @@
+2017-12-13  Pedro Alves  <palves@redhat.com>
+
+	* gdb.cp/cpcompletion.exp: Load completion-support.exp.
+	("expression with namespace"): New set of tests.
+	* gdb.cp/pr9594.cc (Test_NS::foo, Test_NS::bar)
+	(Nested::Test_NS::qux): New.
+	* lib/completion-support.exp (test_gdb_complete_cmd_multiple): Add
+	defaults to 'start_quote_char' and 'end_quote_char' parameters.
+
 2017-12-13  Joel Brobecker  <brobecker@adacore.com>
 
 	* gdb.base/server-del-break.c: New file.
diff --git a/gdb/testsuite/gdb.cp/cpcompletion.exp b/gdb/testsuite/gdb.cp/cpcompletion.exp
index c7883ee3766..62669dc0bd9 100644
--- a/gdb/testsuite/gdb.cp/cpcompletion.exp
+++ b/gdb/testsuite/gdb.cp/cpcompletion.exp
@@ -15,6 +15,8 @@
 
 # This file is part of the gdb testsuite.
 
+load_lib completion-support.exp
+
 # A helper procedure to test location completions restricted by
 # class.
 proc test_class_complete {class expr name matches} {
@@ -85,3 +87,43 @@ gdb_test "complete p foo1.Fo" "p foo1\\.Foofoo"
 
 # Test completion with an anonymous struct.
 gdb_test "complete p a.g" "p a\\.get"
+
+with_test_prefix "expression with namespace" {
+    # Before the scope operator, GDB shows all the symbols whose
+    # fully-qualified name matches the completion word.
+    test_gdb_complete_multiple "p " "Test_NS" "" {
+	"Test_NS"
+	"Test_NS::Nested"
+	"Test_NS::Nested::qux"
+	"Test_NS::bar"
+	"Test_NS::foo"
+    }
+
+    # Unlike in linespecs, tab- and complete-command completion work a
+    # bit differently when completing around the scope operator.  The
+    # matches in the tab-completion case only show the part of the
+    # symbol after the scope, since ':' is a word break character.
+
+    set tab_completion_list {
+	"Nested"
+	"Nested::qux"
+	"bar"
+	"foo"
+    }
+    test_gdb_complete_tab_multiple "p Test_NS:" ":" $tab_completion_list
+    test_gdb_complete_tab_multiple "p Test_NS::" "" $tab_completion_list
+
+    # OTOH, the complete command must show the whole command, with
+    # qualified symbol displayed as entered by the user.
+    set cmd_completion_list {
+	"Test_NS::Nested"
+	"Test_NS::Nested::qux"
+	"Test_NS::bar"
+	"Test_NS::foo"
+    }
+    test_gdb_complete_cmd_multiple "p " "Test_NS:" $cmd_completion_list
+    test_gdb_complete_cmd_multiple "p " "Test_NS::" $cmd_completion_list
+
+    # Add a disambiguating character and we get a unique completion.
+    test_gdb_complete_unique "p Test_NS::f" "p Test_NS::foo"
+}
diff --git a/gdb/testsuite/gdb.cp/pr9594.cc b/gdb/testsuite/gdb.cp/pr9594.cc
index 8fdee84ae1f..54ddaafc0ca 100644
--- a/gdb/testsuite/gdb.cp/pr9594.cc
+++ b/gdb/testsuite/gdb.cp/pr9594.cc
@@ -39,6 +39,19 @@ void Foo::Foofoo ()
 {
 }
 
+namespace Test_NS {
+
+int foo;
+int bar;
+
+namespace Nested {
+
+int qux;
+
+} /* namespace Nested */
+
+} /* namespace Test_NS */
+
 int main ()
 {
   // Anonymous struct with method.
diff --git a/gdb/testsuite/lib/completion-support.exp b/gdb/testsuite/lib/completion-support.exp
index c7cc1c97558..fe5b16a85b8 100644
--- a/gdb/testsuite/lib/completion-support.exp
+++ b/gdb/testsuite/lib/completion-support.exp
@@ -178,7 +178,7 @@ proc test_gdb_complete_cmd_unique { input_line complete_line_re } {
 # complete command displays the COMPLETION_LIST completion list.  Each
 # entry in the list should be prefixed by CMD_PREFIX.
 
-proc test_gdb_complete_cmd_multiple { cmd_prefix completion_word completion_list start_quote_char end_quote_char } {
+proc test_gdb_complete_cmd_multiple { cmd_prefix completion_word completion_list {start_quote_char ""} {end_quote_char ""} } {
     global gdb_prompt
 
     set expected_re [make_cmd_completion_list_re $cmd_prefix $completion_list $start_quote_char $end_quote_char]