gdb: work around negative DW_AT_data_member_location GCC 11 bug

author Simon Marchi <simon.marchi@polymtl.ca>

Thu, 27 Jan 2022 22:35:26 +0000 (17:35 -0500)

committer Simon Marchi <simon.marchi@polymtl.ca>

Thu, 27 Jan 2022 22:35:26 +0000 (17:35 -0500)
author Simon Marchi <simon.marchi@polymtl.ca>
Thu, 27 Jan 2022 22:35:26 +0000 (17:35 -0500)
committer Simon Marchi <simon.marchi@polymtl.ca>
Thu, 27 Jan 2022 22:35:26 +0000 (17:35 -0500)
diff --git a/gdb/dwarf2/cu.c b/gdb/dwarf2/cu.c

index 019165f6e6c5973db55e62f1cd80e2e83910d104..b1fd688188a76fd68bada657ced364d41d91cad6 100644 (file)
--- a/gdb/dwarf2/cu.c
+++ b/gdb/dwarf2/cu.c
@@ -32,6 +32,7 @@ dwarf2_cu::dwarf2_cu (dwarf2_per_cu_data *per_cu,
      checked_producer (false),
      producer_is_gxx_lt_4_6 (false),
      producer_is_gcc_lt_4_3 (false),
+    producer_is_gcc_11 (false),
      producer_is_icc (false),
      producer_is_icc_lt_14 (false),
      producer_is_codewarrior (false),
diff --git a/gdb/dwarf2/cu.h b/gdb/dwarf2/cu.h

index 078479a56988e8dcd8b1db61d00cfdbbb07287cc..bce0a3de63a41a982019a8dc24c3dc048f211b7d 100644 (file)
--- a/gdb/dwarf2/cu.h
+++ b/gdb/dwarf2/cu.h
@@ -253,6 +253,7 @@ public:
    bool checked_producer : 1;
    bool producer_is_gxx_lt_4_6 : 1;
    bool producer_is_gcc_lt_4_3 : 1;
+  bool producer_is_gcc_11 : 1;
    bool producer_is_icc : 1;
    bool producer_is_icc_lt_14 : 1;
    bool producer_is_codewarrior : 1;
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c

index f7cb95b40cba39e1d3632ec2a1e4ed05c3359aa9..1a749eac334fe6a25a511d2268722f1089441500 100644 (file)
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -14320,6 +14320,7 @@ check_producer (struct dwarf2_cu *cu)
      {
        cu->producer_is_gxx_lt_4_6 = major < 4 || (major == 4 && minor < 6);
        cu->producer_is_gcc_lt_4_3 = major < 4 || (major == 4 && minor < 3);
+      cu->producer_is_gcc_11 = major == 11;
      }
    else if (producer_is_icc (cu->producer, &major, &minor))
      {
@@ -14464,6 +14465,19 @@ handle_member_location (struct die_info *die, struct dwarf2_cu *cu,
        if (attr->form_is_constant ())
         {
           LONGEST offset = attr->constant_value (0);
+
+         /* Work around this GCC 11 bug, where it would erroneously use -1
+            data member locations, instead of 0:
+
+              Negative DW_AT_data_member_location
+              https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101378
+            */
+         if (offset == -1 && cu->producer_is_gcc_11)
+           {
+             complaint (_("DW_AT_data_member_location value of -1, assuming 0"));
+             offset = 0;
+           }
+
           field->set_loc_bitpos (offset * bits_per_byte);
         }
        else if (attr->form_is_section_offset ())
diff --git a/gdb/testsuite/gdb.dwarf2/negative-data-member-location.c b/gdb/testsuite/gdb.dwarf2/negative-data-member-location.c

new file mode 100644 (file)

index 0000000..6d8e8df
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/negative-data-member-location.c
@@ -0,0 +1,31 @@
+/* Copyright (C) 2021-2022 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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/>.  */
+
+struct the_struct
+{
+  /* Define the field as an array of char instead of an int to support targets
+     that have sizeof(int) != 4.  */
+  char x[4];
+};
+
+struct the_struct s = { { 0x11, 0x22, 0x22, 0x11 } };
+
+int
+main (void)
+{
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.dwarf2/negative-data-member-location.exp b/gdb/testsuite/gdb.dwarf2/negative-data-member-location.exp

new file mode 100644 (file)

index 0000000..57030d7
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/negative-data-member-location.exp
@@ -0,0 +1,77 @@
+# Copyright 2021-2022 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 our workaround for a GCC 11 bug, where it sometimes puts a -1 value for
+# DW_AT_data_member_location:
+#
+#   Negative DW_AT_data_member_location
+#   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101378
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if { ![dwarf2_support] } {
+    return 0
+}
+
+standard_testfile .c -dw.S
+
+set asm_file [standard_output_file ${srcfile2}]
+
+Dwarf::assemble ${asm_file} {
+    cu {} {
+       DW_TAG_compile_unit {
+           {DW_AT_language @DW_LANG_C99}
+           {DW_AT_producer "GNU C++17 11.1.0 -mtune=generic -march=x86-64 -g3 -O0"}
+           {name ${::srcfile}}
+       } {
+           declare_labels int_label struct_label
+
+           int_label: DW_TAG_base_type {
+               {DW_AT_byte_size 4 DW_FORM_udata}
+               {DW_AT_encoding @DW_ATE_signed}
+               {DW_AT_name "int"}
+           }
+
+           struct_label: DW_TAG_structure_type {
+               {DW_AT_name "the_struct"}
+               {DW_AT_byte_size 4 DW_FORM_udata}
+           } {
+               DW_TAG_member {
+                   {DW_AT_name "field"}
+                   {DW_AT_type :$int_label}
+                   {DW_AT_data_member_location -1 DW_FORM_sdata}
+               }
+           }
+
+           DW_TAG_variable {
+               {DW_AT_name "s"}
+               {DW_AT_type :$struct_label}
+               {DW_AT_location {DW_OP_addr [gdb_target_symbol "s"]} SPECIAL_expr}
+           }
+       }
+    }
+}
+
+if { [prepare_for_testing "failed to prepare" ${testfile} [list $srcfile $asm_file] {nodebug}] } {
+    return
+}
+
+if { ![runto_main] } {
+    return
+}
+
+gdb_test "print /x s" " = {field = 0x11222211}"
+gdb_test "print /x s.field" " = 0x11222211"
author	Simon Marchi <simon.marchi@polymtl.ca>
	Thu, 27 Jan 2022 22:35:26 +0000 (17:35 -0500)
committer	Simon Marchi <simon.marchi@polymtl.ca>
	Thu, 27 Jan 2022 22:35:26 +0000 (17:35 -0500)
gdb/dwarf2/cu.c		patch \| blob \| history
gdb/dwarf2/cu.h		patch \| blob \| history
gdb/dwarf2/read.c		patch \| blob \| history
gdb/testsuite/gdb.dwarf2/negative-data-member-location.c	[new file with mode: 0644]	patch \| blob
gdb/testsuite/gdb.dwarf2/negative-data-member-location.exp	[new file with mode: 0644]	patch \| blob