[PATCH v2] gdb: search local symbols before global symbols in completion

[Oleg Tolmatcev <oleg.tolmatcev@gmail.com>]

When symbol completion is performed from a selected frame, search the
local blocks before scanning minimal symbols and global/static symbols.
This makes completion prefer names that are visible in the current
context, including local variables.

Add a regression test that checks completion prefers a local symbol over
a global symbol with the same name.
---
 gdb/symtab.c                          | 72 +++++++++++++--------------
 gdb/testsuite/gdb.base/break.c        | 21 ++++++++
 gdb/testsuite/gdb.base/completion.exp |  6 +++
 3 files changed, 63 insertions(+), 36 deletions(-)

diff --git a/gdb/symtab.c b/gdb/symtab.c
index 5d5076f2e77..85665bebdf4 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -5931,6 +5931,42 @@ default_collect_symbol_completion_matches_break_on
 
   lookup_name_info lookup_name (sym_text, name_match_type, true);
 
+  /* Search upwards from currently selected frame (so that we can
+     complete on local vars).  Also catch fields of types defined in
+     this places which match our text string.  Only complete on types
+     visible from current context.  */
+
+  b = get_selected_block ();
+  surrounding_static_block = b == nullptr ? nullptr : b->static_block ();
+  surrounding_global_block = b == nullptr ? nullptr : b->global_block ();
+  if (surrounding_static_block != NULL)
+    while (b != surrounding_static_block)
+      {
+	QUIT;
+
+	for (struct symbol *sym : block_iterator_range (b))
+	  {
+	    if (code == TYPE_CODE_UNDEF)
+	      {
+		completion_list_add_symbol (tracker, sym, lookup_name,
+					    sym_text, word);
+		completion_list_add_fields (tracker, sym, lookup_name,
+					    sym_text, word);
+	      }
+	    else if (sym->domain () == STRUCT_DOMAIN
+		     && sym->type ()->code () == code)
+	      completion_list_add_symbol (tracker, sym, lookup_name,
+					  sym_text, word);
+	  }
+
+	/* Stop when we encounter an enclosing function.  Do not stop for
+	   non-inlined functions - the locals of the enclosing function
+	   are in scope for a nested function.  */
+	if (b->function () != NULL && b->inlined_p ())
+	  break;
+	b = b->superblock ();
+      }
+
   /* At this point scan through the misc symbol vectors and add each
      symbol you find to the list.  Eventually we want to ignore
      anything that isn't a text symbol (everything else will be
@@ -5974,42 +6010,6 @@ default_collect_symbol_completion_matches_break_on
 	 SEARCH_ALL_DOMAINS);
     }
 
-  /* Search upwards from currently selected frame (so that we can
-     complete on local vars).  Also catch fields of types defined in
-     this places which match our text string.  Only complete on types
-     visible from current context.  */
-
-  b = get_selected_block ();
-  surrounding_static_block = b == nullptr ? nullptr : b->static_block ();
-  surrounding_global_block = b == nullptr ? nullptr : b->global_block ();
-  if (surrounding_static_block != NULL)
-    while (b != surrounding_static_block)
-      {
-	QUIT;
-
-	for (struct symbol *sym : block_iterator_range (b))
-	  {
-	    if (code == TYPE_CODE_UNDEF)
-	      {
-		completion_list_add_symbol (tracker, sym, lookup_name,
-					    sym_text, word);
-		completion_list_add_fields (tracker, sym, lookup_name,
-					    sym_text, word);
-	      }
-	    else if (sym->domain () == STRUCT_DOMAIN
-		     && sym->type ()->code () == code)
-	      completion_list_add_symbol (tracker, sym, lookup_name,
-					  sym_text, word);
-	  }
-
-	/* Stop when we encounter an enclosing function.  Do not stop for
-	   non-inlined functions - the locals of the enclosing function
-	   are in scope for a nested function.  */
-	if (b->function () != NULL && b->inlined_p ())
-	  break;
-	b = b->superblock ();
-      }
-
   /* Add fields from the file's types; symbols will be added below.  */
 
   if (code == TYPE_CODE_UNDEF)
diff --git a/gdb/testsuite/gdb.base/break.c b/gdb/testsuite/gdb.base/break.c
index 26085d40ca2..c9b74c6a567 100644
--- a/gdb/testsuite/gdb.base/break.c
+++ b/gdb/testsuite/gdb.base/break.c
@@ -23,6 +23,26 @@ extern int marker2 (int a);
 extern void marker3 (char *a, char *b);
 extern void marker4 (long d);
 
+struct completion_global_struct
+{
+  int global_field;
+};
+
+struct completion_local_struct
+{
+  int local_field;
+};
+
+struct completion_global_struct completion_var;
+
+static void
+completion_local_over_global (void)
+{
+  struct completion_local_struct completion_var = { 23 };
+
+  completion_var.local_field++; /* local-completion-breakpoint */
+}
+
 /* We're used by a test that requires malloc, so make sure it is in
    the executable.  */
 void *need_malloc ()
@@ -50,6 +70,7 @@ main (int argc, char **argv, char **envp)
     marker2 (43); /* set breakpoint 20 here */
     marker3 ("stack", "trace"); /* set breakpoint 21 here */
     marker4 (177601976L);
+    completion_local_over_global ();
     /* We're used by a test that requires malloc, so make sure it is
        in the executable.  */
     (void)malloc (1);
diff --git a/gdb/testsuite/gdb.base/completion.exp b/gdb/testsuite/gdb.base/completion.exp
index 44cf649d5b6..9848f21d951 100644
--- a/gdb/testsuite/gdb.base/completion.exp
+++ b/gdb/testsuite/gdb.base/completion.exp
@@ -87,6 +87,12 @@ gdb_test "complete set gnutarget aut" "set gnutarget auto"
 
 gdb_test "complete set cp-abi aut" "set cp-abi auto"
 
+# Check that symbol completion in a selected frame prefers a local
+# symbol over a global symbol with the same name.
+gdb_breakpoint [gdb_get_line_number "local-completion-breakpoint"]
+gdb_continue_to_breakpoint "local-completion-breakpoint"
+gdb_test "complete p completion_var.l" "p completion_var.local_field"
+
 # Test that completion of commands 'target FOO' works well.
 set targets [list "core" "tfile" "exec"]
 
-- 
2.55.0.windows.1