gdb/testsuite/gdb.dwarf2/implref-const.exp

   1 # Copyright 2016-2023 Free Software Foundation, Inc.
   2
   3 # This program is free software; you can redistribute it and/or modify
   4 # it under the terms of the GNU General Public License as published by
   5 # the Free Software Foundation; either version 3 of the License, or
   6 # (at your option) any later version.
   7 #
   8 # This program is distributed in the hope that it will be useful,
   9 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11 # GNU General Public License for more details.
  12 #
  13 # You should have received a copy of the GNU General Public License
  14 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  15
  16 # Test a C++ reference marked with DW_OP_GNU_implicit_pointer.
  17 # The referenced value is a DW_AT_const_value.
  18
  19 require allow_cplus_tests
  20
  21 load_lib dwarf.exp
  22
  23 # This test can only be run on targets which support DWARF-2 and use gas.
  24 require dwarf2_support
  25
  26 # We'll place the output of Dwarf::assemble in implref-const.S.
  27 standard_testfile main.c .S
  28
  29 # ${testfile} is now "implref-const".  srcfile2 is "implref-const.S".
  30 set executable ${testfile}
  31 set asm_file [standard_output_file ${srcfile2}]
  32
  33 # We need to know the size of integer and address types in order
  34 # to write some of the debugging info we'd like to generate.
  35 #
  36 # For that, we ask GDB by debugging our implref-const program.
  37 # Any program would do, but since we already have implref-const
  38 # specifically for this testcase, might as well use that.
  39 if [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] {
  40     return -1
  41 }
  42
  43 # Create the DWARF.  We need a regular variable and a reference to it that'll
  44 # be marked with DW_OP_GNU_implicit_pointer.
  45 Dwarf::assemble ${asm_file} {
  46     cu {} {
  47         DW_TAG_compile_unit {
  48             {DW_AT_language @DW_LANG_C_plus_plus}
  49         } {
  50             declare_labels int_label const_label variable_label ref_label
  51             set int_size [get_sizeof "int" -1]
  52
  53             # gdb always assumes references are implemented as pointers.
  54             set addr_size [get_sizeof "void *" -1]
  55             set var_value 42
  56
  57             int_label: DW_TAG_base_type {
  58                 {DW_AT_byte_size ${int_size} DW_FORM_udata}
  59                 {DW_AT_encoding @DW_ATE_signed}
  60                 {DW_AT_name "int"}
  61             }
  62
  63             ref_label: DW_TAG_reference_type {
  64                 {DW_AT_byte_size ${addr_size} DW_FORM_udata}
  65                 {DW_AT_type :${int_label}}
  66             }
  67
  68             const_label: DW_TAG_const_type {
  69                 {DW_AT_type :${ref_label}}
  70             }
  71
  72             DW_TAG_subprogram {
  73                 {MACRO_AT_func { "main" }}
  74                 {DW_AT_type :${int_label}}
  75                 {DW_AT_external 1 DW_FORM_flag}
  76             } {
  77                 variable_label: DW_TAG_variable {
  78                     {DW_AT_name "var"}
  79                     {DW_AT_type :${int_label}}
  80                     {DW_AT_const_value ${var_value} DW_FORM_udata}
  81                 }
  82
  83                 DW_TAG_variable {
  84                     {DW_AT_name "ref"}
  85                     {DW_AT_type :${const_label}}
  86                     {DW_AT_location {DW_OP_GNU_implicit_pointer ${variable_label} 0} SPECIAL_expr}
  87                 }
  88             }
  89         }
  90     }
  91 }
  92
  93 if [prepare_for_testing "failed to prepare" ${executable} [list ${asm_file} ${srcfile}] {}] {
  94     return -1
  95 }
  96
  97 # DW_OP_GNU_implicit_pointer implementation requires a valid frame.
  98 if ![runto_main] {
  99     return -1
 100 }
 101
 102 # Doing 'print ref' should show us e.g. '(int &) <synthetic pointer>: 42'.
 103 gdb_test "print ref" " = \\(int &\\) <synthetic pointer>: \\\d+"
 104
 105 # The variable isn't located in memory, thus we can't take its address.
 106 gdb_test "print &var" "Can't take address of \"var\" which isn't an lvalue."
 107 gdb_test "print &ref" "Attempt to take address of value not located in memory."
 108
 109 # gdb assumes C++ references are implemented as pointers, and print &(&ref)
 110 # shows us the underlying pointer's address.
 111 # Since in this case there's no physical pointer, gdb should tell us so.
 112 gdb_test "print &(&ref)" "Attempt to take address of value not located in memory."