[PATCH 1/1] gdb: Enable complete to show members of anonymous classes/structs.

[Felix Willgerodt <felix.willgerodt@intel.com>]

This problem shows with anonymous structs/classes:

~~~
  struct {
    private:
      int unique_name_foo = 5;
    public:
      int get() { return unique_name_foo; } /* breakpoint.  */
  } a;
~~~

Before:

~~~
(gdb) p unique_name_foo
$1 = 5
(gdb) complete p unique_name_fo
(gdb)

~~~

After:

~~~
(gdb) p unique_name_foo
$1 = 5
(gdb) complete p unique_name_fo
p unique_name_foo
(gdb)
~~~

As we are able to print the member we should be able to complete on it.
GDB doesn't look at "this" and its members for complete, while it does
when printing.  So I tried fixing that.
I saw that "this" is always represented as a PTR type with the symbol
class LOC_COMPUTED (with g++ 11.3.1, clang++ 10.0.1 and icpx 2022.1).

Not knowing too much about LOC_COMPUTED, I am assuming that this is the right
symbol class for this case and that we should adjust
completion_list_add_fields() for it.
But it could very well be that I missed something.  Any comments welcome!
---
 gdb/symtab.c                          | 18 ++++++++++++------
 gdb/testsuite/gdb.cp/cpcompletion.exp | 16 +++++++++++++---
 gdb/testsuite/gdb.cp/pr9594.cc        |  9 ++++++---
 3 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/gdb/symtab.c b/gdb/symtab.c
index 40887f59d1f..6edeb4ea9db 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -5688,14 +5688,20 @@ completion_list_add_fields (completion_tracker &tracker,
 			    const lookup_name_info &lookup_name,
 			    const char *text, const char *word)
 {
-  if (sym->aclass () == LOC_TYPEDEF)
+  struct type *t = sym->type ();
+
+  if (sym->aclass () == LOC_TYPEDEF
+      || (sym->aclass () == LOC_COMPUTED && t->code () == TYPE_CODE_PTR))
     {
-      struct type *t = sym->type ();
-      enum type_code c = t->code ();
-      int j;
+      /* Anonymous classes/structs are often/always represented as a
+	 pointer with LOC_COMPUTED.  Since we also want to show their
+	 fields as a completion result (as we can print them) we resolve
+	 their target type.  */
+      if (t->code () == TYPE_CODE_PTR)
+	t = TYPE_TARGET_TYPE (t);
 
-      if (c == TYPE_CODE_UNION || c == TYPE_CODE_STRUCT)
-	for (j = TYPE_N_BASECLASSES (t); j < t->num_fields (); j++)
+      if (t->code () == TYPE_CODE_UNION || t->code () == TYPE_CODE_STRUCT)
+	for (int j = TYPE_N_BASECLASSES (t); j < t->num_fields (); j++)
 	  if (t->field (j).name ())
 	    completion_list_add_name (tracker, sym->language (),
 				      t->field (j).name (),
diff --git a/gdb/testsuite/gdb.cp/cpcompletion.exp b/gdb/testsuite/gdb.cp/cpcompletion.exp
index d19ac9c1b69..07ec936e95a 100644
--- a/gdb/testsuite/gdb.cp/cpcompletion.exp
+++ b/gdb/testsuite/gdb.cp/cpcompletion.exp
@@ -76,10 +76,11 @@ test_class_complete Foo F "complete class methods beginning with F" \
 
 # The tests below depend on the current code scope.
 
-set bp_location [gdb_get_line_number "Set breakpoint here" ${srcfile}]
+set bp_1 [gdb_get_line_number "BP1" ${srcfile}]
+set bp_2 [gdb_get_line_number "BP2" ${srcfile}]
 
-if {![runto "${srcfile}:$bp_location"]} {
-    perror "test suppressed"
+if {![runto "${srcfile}:$bp_1"]} {
+    untested "failed to run to first breakpoint"
     return
 }
 
@@ -135,3 +136,12 @@ with_test_prefix "expression with namespace" {
     # Add a disambiguating character and we get a unique completion.
     test_gdb_complete_unique "p Test_NS::f" "p Test_NS::foo"
 }
+
+# Test completion when stopped in a method of an anonymous struct.
+gdb_breakpoint "$srcfile:$bp_2"
+gdb_continue_to_breakpoint "continue to second bp" ".*$srcfile:$bp_2.*"
+
+# We should be able to complete on the members.  We are able to print
+# them after all.
+gdb_test "p unique_name_foo" "= 5"
+gdb_test "complete p unique_name_fo" "p unique_name_foo"
diff --git a/gdb/testsuite/gdb.cp/pr9594.cc b/gdb/testsuite/gdb.cp/pr9594.cc
index 54ddaafc0ca..a3823f9b84f 100644
--- a/gdb/testsuite/gdb.cp/pr9594.cc
+++ b/gdb/testsuite/gdb.cp/pr9594.cc
@@ -56,10 +56,13 @@ int main ()
 {
   // Anonymous struct with method.
   struct {
-    int get() { return 5; }
+    private:
+      int unique_name_foo = 5;
+    public:
+      int get() { return unique_name_foo; } /* BP2.  */
   } a;
   Foo foo1;
-  foo1.set_foo (42);		// Set breakpoint here.
-  a.get();			// Prevent compiler from throwing 'a' away.
+  foo1.set_foo (42);		/* BP1.  */
+  a.get ();
   return 0;
 }
-- 
2.34.3

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