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

[Keith Seitz <keiths at redhat dot com>]

On 07/31/2013 11:46 AM, Tom Tromey wrote:
   ^^^^^^^^^^
Wow, it has taken a bit longer to rotate this back onto my plate than 
I'd hoped. Sorry for the long delay.

> > > > > > "Keith" == Keith Seitz <keiths@redhat.com> writes:
>
> I was also curious why the new type is a TYPE_CODE_NAMESPACE and not a
> TYPE_CODE_TYPEDEF.  Maybe that is too goofy though.

That sounded goofy to me, too. I think neither choice is exactly what we 
(I?) want to describe. I happened to pick TYPE_CODE_NAMESPACE as the 
more appropriate choice.

> Now I'm concerned that bad DWARF can send gdb into an infinite loop
> here.

Ha, yeah. That's a little aggressive on my part.

> Sorry about that.  If compilers don't emit chained imports like this,
> then it is fine to just go back to the old code.

While there's no reason for a compiler to do this, there's also no 
reason one couldn't. So I've decided to play it safe and leave the code, 
fenceposting the maximum number of lookups that the code will do. Right 
now, I've randomly selected 200 imports as the limit.

When this limit is exceeded, it will issue a complaint (and stop 
attempting to read the import). This seems to be the norm in dwarf2read.c.

I've added an additional test case which generates arbitrary depth 
recursive imported declarations and checks for the complaint.

Keith

ChangeLog
2013-09-17  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
2013-09-17  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 86f19de..b91bcdc 100644
--- a/gdb/cp-support.c
+++ b/gdb/cp-support.c
@@ -198,8 +198,9 @@ 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;
@@ -210,6 +211,13 @@ 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 4b30e6e..cd954ee 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -1548,6 +1548,8 @@ 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);
 
@@ -6235,6 +6237,9 @@ 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;
 	    }
@@ -6506,6 +6511,7 @@ 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,
@@ -7762,6 +7768,10 @@ 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
@@ -7804,6 +7814,7 @@ 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:
@@ -8222,6 +8233,66 @@ 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)
+    {
+      int num;
+      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.  */
+#define MAX_NESTED_IMPORTED_DECLARATIONS 100
+      for (num = 0; num  < MAX_NESTED_IMPORTED_DECLARATIONS; ++num)
+	{
+	  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 (num == MAX_NESTED_IMPORTED_DECLARATIONS)
+	{
+	  complaint (&symfile_complaints,
+		     _("DIE at 0x%x has too many recursively imported "
+		       "declarations"), d->offset.sect_off);
+	  return 0;
+	}
+
+      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
@@ -14092,7 +14163,8 @@ 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);
@@ -16810,6 +16882,7 @@ 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..61bf72f
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/nsalias.exp
@@ -0,0 +1,322 @@
+# 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 "${ns}::Innermost" "outer::inner::innermost" 2
+}
+
+# Generate another objfile with nested imported declarations.
+
+set imports {
+    declare_labels n0_label
+
+    n0_label: DW_TAG_namespace {
+	{name n0}
+    } {
+	DW_TAG_variable {
+	    {name x}
+	    {type :$int_label}
+	    {const_value 3 DW_FORM_data1}
+	}
+    }
+
+    declare_labels n0_import
+    n0_import: imported_declaration {
+	{name N0}
+	{import :$n0_label}
+    }
+}
+
+for {set i 1} {$i <= 100} {incr i} {
+    append imports [format "
+	declare_labels n%d_import
+	n%d_import: imported_declaration {
+	    {name N%d}
+	    {import :\$n%d_import}
+	}" $i $i $i [expr {$i - 1}]]
+}
+
+standard_testfile .cc nsalias-r-dw.S
+
+set asm_file [standard_output_file $srcfile2]
+set the_dwarf [format {
+    cu {} {
+	compile_unit {{language @DW_LANG_C_plus_plus}} {
+	    declare_labels int_label n0_label
+
+	    int_label: base_type {
+		{name int}
+		{encoding @DW_ATE_signed}
+		{byte_size 4 DW_FORM_sdata}
+	    }
+
+%s
+	}
+    }
+} $imports]
+
+Dwarf::assemble $asm_file $the_dwarf
+
+if {[gdb_compile $asm_file ${binfile}3.o object {nodebug}] != ""} {
+    return -1
+}
+
+if {[gdb_compile [list ${binfile}1.o ${binfile}3.o] \
+	 ${binfile}-r executable {c++}] != ""} {
+    return -1
+}
+
+clean_restart ${testfile}-r
+
+gdb_test_no_output "set complaints 1"
+gdb_test "print N100::x" \
+    ".* has too many recursively imported declarations.*" \
+    "compaint for too many recursively imported declarations"
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"
+    }
+}