Re: [RFA] Fix namespace aliases (c++/7539, c++/10541)

[Keith Seitz <keiths at redhat dot com>]

On 07/29/2013 01:28 PM, Tom Tromey wrote:
> Ok, I think I see what is going on here.  For an alias A we have a
> symbol named A, whose type is the type of the referent.
>
> I think the comment here is a bit confusing since it says "its name",
> but really it means the symbol's type's name.

I've updated the comment to make this less ambiguous.

> I'm curious how this copes with some other situations.
>
> For example, an import of a declaration from another namespace, where
> the imported declaration is itself an import.

I wouldn't expect a compiler to actually do this (gcc does not), but 
I've updated the code to handle this case.

BTW, while investigating this, I found a buglet in my original patch. At 
the last minute, I thought I'd be paranoid and add a test for 
DW_AT_name. Unfortunately, in my haste, I fetched DW_AT_name /after/ 
DW_AT_import. That was bad. Very bad. I've fixed this in this version.

> Or, if the program is stopped in a function inside a namespace, can the
> user use the "local" (not fully qualified) alias?

This particular feature is c++/13884. That is an entirely different 
problem. I've updated the bug with some comments explaining what's going on.

> I don't think either of these situations is tested.

I've added tests for the recursive alias. If/when I get around to fixing 
13384, I'll add tests for that.

> Keith> @@ -7732,6 +7736,32 @@ process_die (struct die_info *die, struct dwarf2_cu *cu)
> Keith>        read_module (die, cu);
> Keith>        break;
> Keith>      case DW_TAG_imported_declaration:
> Keith> +      {
> Keith> +	struct attribute *attr;
> Keith> +
> Keith> +	attr = dwarf2_attr (die, DW_AT_import, cu);
> Keith> +	if (attr != NULL)
> Keith> +	  {
> Keith> +	    /* If the die does not have a name, this is not a namespace
> Keith> +	       alias.  */
> Keith> +	    attr = dwarf2_attr (die, DW_AT_name, cu);
> Keith> +	    if (attr != NULL)
> Keith> +	      {
>
> It's customary not to have a body of code in process_die, but to instead
> call a helper function.

Done.

Updated patch attached.

Keith

ChangeLog
2013-07-30  Keith Seitz  <keiths@redhat.com>

	PR c++/7539
	PR c++/10541
	* cp-support.c (insepct_type): Add support for substituting
	namespace aliases, too.
	* dwarf2read.c (scan_partial_symbols): Add a partial symbol
	for DW_TAG_imported_declaration.
	(add_partial_symbol): Likewise.
	(process_die): Handle namespace aliases with
	read_namespace_alias.
	(die_needs_namespace): Add DW_TAG_imported_declaration.
	(read_namespace_alias): New function.
	(load_partial_dies): Load DW_TAG_imported_declaration, too.
	(new_symbol_full): Handle DW_TAG_imported_declaration.

testsuite/ChangeLog
2013-07-30  Keith Seitz  <keiths@redhat.com>

	PR c++/7935
	PR c++/10541
	* gdb.cp/nsalias.exp: New file.
	* gdb.cp/nsalias.cc: New file.
	* gdb.cp/nsrecurs.exp: Remove kfails. Conditionally run
	tests only on known, working compiler versions.


diff --git a/gdb/cp-support.c b/gdb/cp-support.c
index 3c1442d..087bf0b 100644
--- a/gdb/cp-support.c
+++ b/gdb/cp-support.c
@@ -200,8 +200,9 @@ inspect_type (struct demangle_parse_info *info,
 	  return 0;
 	}
 
-      /* If the type is a typedef, replace it.  */
-      if (TYPE_CODE (otype) == TYPE_CODE_TYPEDEF)
+      /* If the type is a typedef or namespace alias, replace it.  */
+      if (TYPE_CODE (otype) == TYPE_CODE_TYPEDEF
+	  || TYPE_CODE (otype) == TYPE_CODE_NAMESPACE)
 	{
 	  long len;
 	  int is_anon;
@@ -212,6 +213,13 @@ inspect_type (struct demangle_parse_info *info,
 	  /* Get the real type of the typedef.  */
 	  type = check_typedef (otype);
 
+	  /* If the symbol is a namespace and its type name is no different
+	     than the name we looked up, this symbol is not a namespace
+	     alias and does not need to be substituted.  */
+	  if (TYPE_CODE (otype) == TYPE_CODE_NAMESPACE
+	      && strcmp (TYPE_NAME (type), name) == 0)
+	    return 0;
+
 	  is_anon = (TYPE_TAG_NAME (type) == NULL
 		     && (TYPE_CODE (type) == TYPE_CODE_ENUM
 			 || TYPE_CODE (type) == TYPE_CODE_STRUCT
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 04993c2..89799e9 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -1537,6 +1537,8 @@ static void read_module (struct die_info *die, struct dwarf2_cu *cu);
 
 static void read_import_statement (struct die_info *die, struct dwarf2_cu *);
 
+static int read_namespace_alias (struct die_info *die, struct dwarf2_cu *cu);
+
 static struct type *read_module_type (struct die_info *die,
 				      struct dwarf2_cu *cu);
 
@@ -6244,6 +6246,9 @@ scan_partial_symbols (struct partial_die_info *first_die, CORE_ADDR *lowpc,
 			       cu->per_cu->imported_symtabs, per_cu);
 	      }
 	      break;
+	    case DW_TAG_imported_declaration:
+	      add_partial_symbol (pdi, cu);
+	      break;
 	    default:
 	      break;
 	    }
@@ -6515,6 +6520,7 @@ add_partial_symbol (struct partial_die_info *pdi, struct dwarf2_cu *cu)
 			   &objfile->static_psymbols,
 			   0, (CORE_ADDR) 0, cu->language, objfile);
       break;
+    case DW_TAG_imported_declaration:
     case DW_TAG_namespace:
       add_psymbol_to_list (actual_name, strlen (actual_name),
 			   built_actual_name != NULL,
@@ -7732,6 +7738,10 @@ process_die (struct die_info *die, struct dwarf2_cu *cu)
       read_module (die, cu);
       break;
     case DW_TAG_imported_declaration:
+      cu->processing_has_namespace_info = 1;
+      if (read_namespace_alias (die, cu))
+	break;
+      /* The declaration is not a global namespace alias: fall through.  */
     case DW_TAG_imported_module:
       cu->processing_has_namespace_info = 1;
       if (die->child != NULL && (die->tag == DW_TAG_imported_declaration
@@ -7774,6 +7784,7 @@ die_needs_namespace (struct die_info *die, struct dwarf2_cu *cu)
     case DW_TAG_enumerator:
     case DW_TAG_subprogram:
     case DW_TAG_member:
+    case DW_TAG_imported_declaration:
       return 1;
 
     case DW_TAG_variable:
@@ -8192,6 +8203,56 @@ dwarf2_physname (const char *name, struct die_info *die, struct dwarf2_cu *cu)
   return retval;
 }
 
+/* Inspect DIE in CU for a namespace alias.  If one exists, record
+   a new symbol for it.
+
+   Returns 1 if a namespace alias was recorded, 0 otherwise.  */
+
+static int
+read_namespace_alias (struct die_info *die, struct dwarf2_cu *cu)
+{
+  struct attribute *attr;
+
+  /* If the die does not have a name, this is not a namespace
+     alias.  */
+  attr = dwarf2_attr (die, DW_AT_name, cu);
+  if (attr != NULL)
+    {
+      struct die_info *d = die;
+      struct dwarf2_cu *imported_cu = cu;
+
+      /* If the compiler has nested DW_AT_imported_declaration DIEs,
+	 keep inspecting DIEs until we hit the underlying import.  */
+      while (1)
+	{
+	  attr = dwarf2_attr (d, DW_AT_import, cu);
+	  if (attr == NULL)
+	    break;
+
+	  d = follow_die_ref (d, attr, &imported_cu);
+	  if (d->tag != DW_TAG_imported_declaration)
+	    break;
+	}
+
+      if (attr != NULL)
+	{
+	  struct type *type;
+	  sect_offset offset = dwarf2_get_ref_die_offset (attr);
+
+	  type = get_die_type_at_offset (offset, cu->per_cu);
+	  if (type != NULL && TYPE_CODE (type) == TYPE_CODE_NAMESPACE)
+	    {
+	      /* This declaration is a global namespace alias.  Add
+		 a symbol for it whose type is the aliased namespace.  */
+	      new_symbol (die, type, cu);
+	      return 1;
+	    }
+	}
+    }
+
+  return 0;
+}
+
 /* Read the import statement specified by the given die and record it.  */
 
 static void
@@ -14013,7 +14074,8 @@ load_partial_dies (const struct die_reader_specs *reader,
 	  && abbrev->tag != DW_TAG_namespace
 	  && abbrev->tag != DW_TAG_module
 	  && abbrev->tag != DW_TAG_member
-	  && abbrev->tag != DW_TAG_imported_unit)
+	  && abbrev->tag != DW_TAG_imported_unit
+	  && abbrev->tag != DW_TAG_imported_declaration)
 	{
 	  /* Otherwise we skip to the next sibling, if any.  */
 	  info_ptr = skip_one_die (reader, info_ptr + bytes_read, abbrev);
@@ -16731,6 +16793,7 @@ new_symbol_full (struct die_info *die, struct type *type, struct dwarf2_cu *cu,
 			   ? &global_symbols : cu->list_in_scope);
 	  }
 	  break;
+	case DW_TAG_imported_declaration:
 	case DW_TAG_namespace:
 	  SYMBOL_ACLASS_INDEX (sym) = LOC_TYPEDEF;
 	  list_to_add = &global_symbols;
diff --git a/gdb/testsuite/gdb.cp/nsalias.cc b/gdb/testsuite/gdb.cp/nsalias.cc
new file mode 100644
index 0000000..be2dfbe
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/nsalias.cc
@@ -0,0 +1,23 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2013 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+int
+main ()
+{
+  return 0;
+}
+
diff --git a/gdb/testsuite/gdb.cp/nsalias.exp b/gdb/testsuite/gdb.cp/nsalias.exp
new file mode 100644
index 0000000..18f32b2
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/nsalias.exp
@@ -0,0 +1,254 @@
+# Copyright 2013 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test namespace aliases.
+# PRs c++/7935, c++/10541
+
+load_lib dwarf.exp
+
+if {![dwarf2_support]} {
+    return 0
+}
+
+if {[skip_cplus_tests]} {
+    continue
+}
+
+standard_testfile .cc nsalias-dw.S
+
+# Make the DWARF used for the test.  This is necessary to work
+# around compiler issues.  Not all versions of gcc output the
+# correct debuginfo we need.
+#
+# This should create the equivalent DWARF to:
+#
+# namespace outer
+# {
+#   namespace inner
+#   {
+#     namespace innermost
+#     {
+#       const int x = 2;
+#       int foo (void) { return x; }
+#     }
+#
+#     namespace Innermost = innermost;
+#
+#     const int x = 1;
+#     int foo (void) { return x + Innermost::foo (); }
+#   }
+#
+#   namespace Inner = inner;
+#
+#   const int x = 0;
+#   int foo (void) { return x + Inner::foo (); }
+# }
+#
+# namespace Outer = outer;
+# namespace oi = Outer::Inner;
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    cu {} {
+	compile_unit {{language @DW_LANG_C_plus_plus}} {
+	    declare_labels int_label outer_label inner_label innermost_label
+	    declare_labels im_foo_label i_foo_label o_foo_label
+	    declare_labels OuterInner_label oi1_label oi2_label
+
+	    int_label: base_type {
+		{name int}
+		{encoding @DW_ATE_signed}
+		{byte_size 4 DW_FORM_sdata}
+	    }
+
+	    outer_label: DW_TAG_namespace {
+		{name outer}
+	    } {
+		inner_label: DW_TAG_namespace {
+		    {name inner}
+		} {
+		    innermost_label: DW_TAG_namespace {
+			{name innermost}
+		    } {
+			DW_TAG_variable {
+			    {name x}
+			    {type :$int_label}
+			    {const_value 2 DW_FORM_data1}
+			}
+
+			im_foo_label: DW_TAG_subprogram {
+			    {name foo}
+			    {external 1}
+			    {declaration 1}
+			}
+		    }
+
+		    imported_declaration {
+			{name Innermost}
+			{import :$innermost_label}
+		    }
+
+		    DW_TAG_variable {
+			{name x}
+			{type :$int_label}
+			{const_value 1 DW_FORM_data1}
+		    }
+
+		    i_foo_label: subprogram {
+			{name foo}
+			{external 1}
+			{declaration 1}
+		    }
+		}
+
+		OuterInner_label: imported_declaration {
+		    {name Inner}
+		    {import :$inner_label}
+		}
+
+		DW_TAG_variable {
+		    {name x}
+		    {type :$int_label}
+		    {const_value 0 DW_FORM_data1}
+		}
+
+		o_foo_label: subprogram {
+		    {name foo}
+		    {external 1}
+		    {declaration 1}
+		}
+	    }
+
+	    imported_declaration {
+		{name Outer}
+		{import :$outer_label}
+	    }
+
+	    oi1_label: imported_declaration {
+		{name oi1}
+		{import :$OuterInner_label}
+	    }
+
+	    oi2_label: imported_declaration {
+		{name oi2}
+		{import :$oi1_label}
+	    }
+
+	    imported_declaration {
+		{name oi3}
+		{import :$oi2_label}
+	    }
+
+	    subprogram {
+		{specification :$im_foo_label}
+		{low_pc 0x0}
+		{high_pc 0x1}
+	    }
+
+	    subprogram {
+		{specification :$i_foo_label}
+		{low_pc 0x2}
+		{high_pc 0x3}
+	    }
+
+	    subprogram {
+		{specification :$o_foo_label}
+		{low_pc 0x4}
+		{high_pc 0x5}
+	    }
+	}
+    }
+}
+
+if {[gdb_compile $srcdir/$subdir/$srcfile ${binfile}1.o \
+	 object {c++ debug}] != ""} {
+    return -1
+}
+
+if {[gdb_compile $asm_file ${binfile}2.o object {nodebug}] != ""} {
+    return -1
+}
+
+if {[gdb_compile [list ${binfile}1.o ${binfile}2.o] \
+	 $binfile executable {c++}] != ""} {
+    return -1
+}
+
+clean_restart $testfile
+
+# A procedure to run various tests on aliased namespaces.
+proc do_alias_tests {ns {real ""} {x ""}} {
+
+    # The "real" namespace is simply NS in all lowercase.
+    if {$real == ""} {
+	set real [string tolower $ns]
+    }
+
+    # The value of `x' is the number of '::' in NS.
+    if {$x == ""} {
+	set x [expr {[llength [split $ns ":"]] / 2}]
+    }
+
+    # Test "whatis"
+    gdb_test "whatis $ns" "type = $real"
+
+    # Test "ptype"
+    gdb_test "ptype $ns" "type = namespace $real"
+
+    # Print 'x'
+    send_log "expecting x = $x\n"
+    gdb_test "print ${ns}::x" " = $x"
+
+    # Attempt to list the function.
+    gdb_test_no_output "list ${ns}::foo"
+
+    # Attempt to break on the start of the function.
+    gdb_breakpoint "*${ns}::foo"
+
+    # And then erase it
+    with_test_prefix "($ns)" {
+	gdb_test_no_output "delete \$bpnum"
+    }
+}
+
+# This is a list of all the permutations to be tested.  For troubleshooting
+# purposes, this list is explicitly enumerated.
+
+set permutations {}
+lappend permutations "outer"
+lappend permutations "Outer"
+lappend permutations "outer::inner"
+lappend permutations "Outer::inner"
+lappend permutations "outer::Inner"
+lappend permutations "Outer::Inner"
+lappend permutations "outer::inner::innermost"
+lappend permutations "outer::inner::Innermost"
+lappend permutations "outer::Inner::innermost"
+lappend permutations "outer::Inner::Innermost"
+lappend permutations "Outer::inner::innermost"
+lappend permutations "Outer::inner::Innermost"
+lappend permutations "Outer::Inner::innermost"
+lappend permutations "Outer::Inner::Innermost"
+
+foreach p $permutations {
+    do_alias_tests $p
+}
+
+# Test recursively imported aliases.
+foreach ns {"oi1" "oi2" "oi3"} {
+    do_alias_tests $ns "outer::inner" 1
+    do_alias_tests "${ns}::innermost" "outer::inner::innermost" 2
+    do_alias_tests "${ns}::Innermost" "outer::inner::innermost" 2
+}
diff --git a/gdb/testsuite/gdb.cp/nsrecurs.exp b/gdb/testsuite/gdb.cp/nsrecurs.exp
index 0537e89..9cf4331 100644
--- a/gdb/testsuite/gdb.cp/nsrecurs.exp
+++ b/gdb/testsuite/gdb.cp/nsrecurs.exp
@@ -52,8 +52,10 @@ gdb_test "print xx" "= 999"
 # Test printing using recursive namespace
 # aliases.
 
-setup_kfail "gdb/10541" "*-*-*"
-gdb_test "ptype G::GF" "= namespace F"
+if {![test_compiler_info {gcc-[0-3]-*}]} {
+    gdb_test "ptype G::GF" "= namespace F"
 
-setup_kfail "gdb/10541" "*-*-*"
-gdb_test "print G::GF::FE::ex" "= 9999"
+    if {![test_compiler_info {gcc-4-[0-3]-*}]} {
+	gdb_test "print G::GF::FE::ex" "= 9999"
+    }
+}