RE: [PATCH] Debug support for global alias variable

["Natarajan, Kavitha" <Kavitha.Natarajan@amd.com>]

[AMD Official Use Only]

Can this patch be pushed to upstream?

> -----Original Message-----
> From: Natarajan, Kavitha
> Sent: Wednesday, April 20, 2022 5:47 PM
> To: Pedro Alves <pedro@palves.net>; Tom Tromey <tom@tromey.com>;
> Natarajan, Kavitha via Gdb-patches <gdb-patches@sourceware.org>
> Cc: George, Jini Susan <JiniSusan.George@amd.com>; Parasuraman,
> Hariharan <Hariharan.Parasuraman@amd.com>
> Subject: RE: [PATCH] Debug support for global alias variable
>
> > Could you please go over the patch tweaking the new gdb_test_multiple
> > calls to follow the same pattern, please?
> >
>
> Thank you Pedro for your suggestions. I have incorporated the changes for all
> get_test_multiple calls and updated the patch.
>
> Regards,
> Kavitha
> ==========================================================
> ====================
> When clang emits the dwarf information of global alias variable as
> DW_TAG_imported_declaration, gdb does not handle it. GDB reads this tag
> as C++/fortran imported declaration (type alias, namespace alias and fortran
> module). Added support to handle this tag as alias variable.
>
> This change fixes the failure in gdb.base/symbol-alias.exp testcase.
> This testcase is also updated to test nested (recursive) alias.
> ---
>  gdb/dwarf2/read.c                       | 60 ++++++++++++++---------
>  gdb/testsuite/gdb.base/symbol-alias.exp | 63
> ++++++++++++++++++++++++-  gdb/testsuite/gdb.base/symbol-alias2.c  |
> 16 +++++++
>  3 files changed, 116 insertions(+), 23 deletions(-)
>
> diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c index
> 6dcd446e5f4..d0c95459d8f 100644
> --- a/gdb/dwarf2/read.c
> +++ b/gdb/dwarf2/read.c
> @@ -957,6 +957,10 @@ static void build_type_psymtabs_reader
> (cutu_reader *reader,
>
>  static void dwarf2_build_psymtabs_hard (dwarf2_per_objfile *per_objfile);
>
> +static void var_decode_location (struct attribute *attr,
> +                              struct symbol *sym,
> +                              struct dwarf2_cu *cu);
> +
>  static unsigned int peek_abbrev_code (bfd *, const gdb_byte *);
>
>  static const gdb_byte *read_attribute (const struct die_reader_specs *, @@
> -1134,7 +1138,7 @@ static struct using_direct **using_directives (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 bool read_alias (struct die_info *die, struct dwarf2_cu *cu);
>
>  static struct type *read_module_type (struct die_info *die,
>                                     struct dwarf2_cu *cu);
> @@ -8728,9 +8732,9 @@ process_die (struct die_info *die, struct dwarf2_cu
> *cu)
>        break;
>      case DW_TAG_imported_declaration:
>        cu->processing_has_namespace_info = true;
> -      if (read_namespace_alias (die, cu))
> +      if (read_alias (die, cu))
>       break;
> -      /* The declaration is not a global namespace alias.  */
> +      /* The declaration is not a global namespace or variable alias.
> + */
>        /* Fall through.  */
>      case DW_TAG_imported_module:
>        cu->processing_has_namespace_info = true; @@ -9198,18 +9202,19 @@
> 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.
> +/* Inspect DIE in CU for a namespace alias or a variable
> +   with alias attribute. If one exists, record a new symbol
> +   for it.
>
> -   Returns 1 if a namespace alias was recorded, 0 otherwise.  */
> +   Returns "true" if an alias was recorded, "false" otherwise.  */
>
> -static int
> -read_namespace_alias (struct die_info *die, struct dwarf2_cu *cu)
> +static bool
> +read_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.  */
> +  /* If the die does not have a name, this is not a namespace alias
> +     or variable alias.  */
>    attr = dwarf2_attr (die, DW_AT_name, cu);
>    if (attr != NULL)
>      {
> @@ -9235,26 +9240,39 @@ read_namespace_alias (struct die_info *die,
> struct dwarf2_cu *cu)
>       {
>         complaint (_("DIE at %s has too many recursively imported "
>                      "declarations"), sect_offset_str (d->sect_off));
> -       return 0;
> +       return false;
>       }
>
>        if (attr != NULL)
>       {
>         struct type *type;
> -       sect_offset sect_off = attr->get_ref_die_offset ();
> -
> -       type = get_die_type_at_offset (sect_off, cu->per_cu, cu-
> >per_objfile);
> -       if (type != NULL && type->code () == TYPE_CODE_NAMESPACE)
> +       if (d->tag == DW_TAG_variable)
>           {
> -           /* 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;
> +           /* This declaration is a C/C++ global variable alias. Add
> +              a symbol for it whose type is same as aliased variable.  */
> +           type = die_type (d, imported_cu);
> +           struct symbol *sym = new_symbol (die, type, cu);
> +           attr = dwarf2_attr (d, DW_AT_location, imported_cu);
> +           sym->set_aclass_index (LOC_UNRESOLVED);
> +           if (attr != nullptr)
> +             var_decode_location (attr, sym, cu);
> +           return true;
> +         }
> +       else
> +         {
> +           sect_offset sect_off = attr->get_ref_die_offset ();
> +           type = get_die_type_at_offset (sect_off, cu->per_cu, cu-
> >per_objfile);
> +           if (type != NULL && type->code () == 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 true;
> +             }
>           }
>       }
>      }
> -
> -  return 0;
> +  return false;
>  }
>
>  /* Return the using directives repository (global or local?) to use in the diff --
> git a/gdb/testsuite/gdb.base/symbol-alias.exp
> b/gdb/testsuite/gdb.base/symbol-alias.exp
> index 2b53cc31053..1024954b0cb 100644
> --- a/gdb/testsuite/gdb.base/symbol-alias.exp
> +++ b/gdb/testsuite/gdb.base/symbol-alias.exp
> @@ -15,6 +15,9 @@
>  # along with this program.  If not, see <http://www.gnu.org/licenses/>.
>
>  standard_testfile symbol-alias.c symbol-alias2.c
> +set using_clang [test_compiler_info clang-*] set old_clang [expr
> +[test_compiler_info {clang-1[0-3]-*-*}] \
> +              || [test_compiler_info {clang-[1-9]-*}]]
>
>  if { [prepare_for_testing "failed to prepare" ${testfile} [list $srcfile $srcfile2]]
> } {
>      return -1
> @@ -31,6 +34,62 @@ foreach f {"func" "func_alias"} {  }
>
>  # Variables.
> -foreach v {"g_var_s" "g_var_s_alias"} {
> -    gdb_test "p $v" "= {field1 = 1, field2 = 2}"
> +gdb_test "p g_var_s" "= {field1 = 1, field2 = 2}"
> +foreach v {"g_var_s_alias" "g_var_s_alias2"} {
> +    gdb_test_multiple "p $v" "print alias variable $v" {
> +     -re -wrap " = {field1 = 1, field2 = 2}" {
> +         pass $gdb_test_name
> +     }
> +     -re -wrap "has unknown type; cast it to its declared type" {
> +         if { $old_clang } {
> +             xfail $gdb_test_name
> +         } else {
> +             fail $gdb_test_name
> +         }
> +     }
> +    }
> +}
> +
> +# Static Variable.
> +gdb_test "p g_var" " = 1"
> +gdb_test_multiple "p g_var_alias" "print alias of static variable" {
> +    -re -wrap " = 1" {
> +     pass $gdb_test_name
> +    }
> +    -re -wrap "has unknown type; cast it to its declared type" {
> +     if { $old_clang } {
> +       xfail $gdb_test_name
> +     } else {
> +       fail $gdb_test_name
> +     }
> +    }
> +}
> +
> +# Deferred Variable.
> +gdb_test "p g_def_var" " = 2"
> +gdb_test_multiple "p g_def_var_alias" "print alias of deferred variable" {
> +    -re -wrap " = 2" {
> +     pass $gdb_test_name
> +    }
> +    -re -wrap "has unknown type; cast it to its declared type" {
> +     if { $using_clang } {
> +       xfail $gdb_test_name
> +     } else {
> +       fail $gdb_test_name
> +     }
> +    }
> +}
> +
> +# Alias of deferred Variable alias.
> +gdb_test_multiple "p g_def_var2_alias2" "print alias of alias of deferred
> variable" {
> +    -re -wrap " = 3" {
> +     pass $gdb_test_name
> +    }
> +    -re -wrap "has unknown type; cast it to its declared type" {
> +     if { $old_clang } {
> +       xfail $gdb_test_name
> +     } else {
> +       fail $gdb_test_name
> +     }
> +    }
>  }
> diff --git a/gdb/testsuite/gdb.base/symbol-alias2.c
> b/gdb/testsuite/gdb.base/symbol-alias2.c
> index 34f4e121e25..41d4b6a53e5 100644
> --- a/gdb/testsuite/gdb.base/symbol-alias2.c
> +++ b/gdb/testsuite/gdb.base/symbol-alias2.c
> @@ -23,6 +23,8 @@ struct S
>
>  struct S g_var_s = { 1, 2 };
>
> +static int g_var = 1;
> +
>  #ifdef __cplusplus
>  /* So that the alias attribute below work without having to figure out
>     this function's mangled name.  */
> @@ -38,3 +40,17 @@ func (void)
>  struct S *func_alias (void) __attribute__ ((alias ("func")));
>
>  extern struct S g_var_s_alias __attribute__ ((alias ("g_var_s")));
> +
> +extern struct S g_var_s_alias2 __attribute__ ((alias
> +("g_var_s_alias")));
> +
> +extern int g_var_alias __attribute__ ((alias ("g_var")));
> +
> +extern int g_def_var_alias __attribute__ ((alias ("g_def_var")));
> +
> +int g_def_var = 2;
> +
> +extern int g_def_var2_alias __attribute__ ((alias ("g_def_var2")));
> +
> +int g_def_var2 = 3;
> +
> +extern int g_def_var2_alias2 __attribute__ ((alias
> +("g_def_var2_alias")));
> --
> 2.25.1