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      1 # Copyright 2016-2024 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."
    113