From: Martin Galvan Date: Mon, 18 Apr 2016 13:58:14 +0000 (-0300) Subject: Fix gdb crash when trying to print the address of a synthetic C++ reference X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=a22df60ad216517bbca4b391bec09f9ded06ab7b;p=binutils-gdb.git Fix gdb crash when trying to print the address of a synthetic C++ reference After compiling a program which uses C++ references some optimizations may convert the references into synthetic "pointers". Trying to print the address of one of such synthetic references causes gdb to crash with the following error: (gdb) print &ref /build/buildd/gdb-7.7.1/gdb/dwarf2loc.c:1624: internal-error: Should not be able to create a lazy value with an enclosing type A problem internal to GDB has been detected, further debugging may prove unreliable. Apparently, what was causing it was that value_addr returns a copy of the value that represents the reference with its type set to T* instead of T&. However, its enclosing_type is left untouched, which fails a check made in read_pieced_value. We only see the crash happen for references that are synthetic because they're treated as pieced values, thus the call to read_pieced_value. On a related note, it seems that in general there are all sorts of breakage when working with synthetic references. This is reported here: https://sourceware.org/bugzilla/show_bug.cgi?id=19893 gdb/ChangeLog: 2016-04-18 Martin Galvan * valops.c (value_addr): For C++ references, set the copied value's enclosing_type as well. gdb/testsuite/ChangeLog: 2016-04-18 Martin Galvan * gdb.dwarf2/implref.exp: New file. --- diff --git a/gdb/ChangeLog b/gdb/ChangeLog index daf86d9e7f6..3af2212a629 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2016-04-18 Martin Galvan + + * valops.c (value_addr): For C++ references, set the copied value's + enclosing_type as well. + 2016-04-18 Yao Qi Revert: diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index dcff95fc65e..892b0d34a49 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,7 @@ +2016-04-18 Martin Galvan + + * gdb.dwarf2/implref.exp: New file. + 2016-04-18 Bernhard Heckel * gdb.fortran/common-block.exp: Use type naming defined in lib fortran. diff --git a/gdb/testsuite/gdb.dwarf2/implref.exp b/gdb/testsuite/gdb.dwarf2/implref.exp new file mode 100644 index 00000000000..ca4766e1088 --- /dev/null +++ b/gdb/testsuite/gdb.dwarf2/implref.exp @@ -0,0 +1,98 @@ +# Copyright 2016 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 . + +# Test C++ references marked with DW_OP_GNU_implicit_pointer. + +# TODO: Add more test statements after fixing bug #19893: +# https://sourceware.org/bugzilla/show_bug.cgi?id=19893. + +load_lib dwarf.exp + +# This test can only be run on targets which support DWARF-2 and use gas. +if {![dwarf2_support]} { + return 0 +} + +# We'll place the output of Dwarf::assemble in implref.S. +standard_testfile main.c .S + +# ${testfile} is now "implref". srcfile2 is "implref.S". +set executable ${testfile} +set asm_file [standard_output_file ${srcfile2}] + +# Create the DWARF. We need a regular variable and a reference to it that'll +# be marked with DW_OP_GNU_implicit_pointer. +Dwarf::assemble $asm_file { + global srcdir subdir srcfile + + cu { version 3 addr_size 4 } { + DW_TAG_compile_unit { + {DW_AT_producer "GNU C++ 4.8.4"} + {DW_AT_language @DW_LANG_C_plus_plus} + } { + declare_labels int_label const_label variable_label ref_label + + int_label: DW_TAG_base_type { + {DW_AT_byte_size 4 DW_FORM_udata} + {DW_AT_encoding @DW_ATE_signed} + {DW_AT_name "int"} + } + + ref_label: DW_TAG_reference_type { + {DW_AT_byte_size 4 DW_FORM_udata} + {DW_AT_type :${int_label}} + } + + const_label: DW_TAG_const_type { + {DW_AT_type :${ref_label}} + } + + DW_TAG_subprogram { + {MACRO_AT_func { "main" "${srcdir}/${subdir}/${srcfile}" }} + {DW_AT_type :${int_label}} + {DW_AT_external 1 DW_FORM_flag} + } { + variable_label: DW_TAG_variable { + {DW_AT_name "var"} + {DW_AT_type :${int_label}} + {DW_AT_const_value 42 DW_FORM_udata} + } + + DW_TAG_variable { + {DW_AT_name "ref"} + {DW_AT_type :${const_label}} + {DW_AT_location {DW_OP_GNU_implicit_pointer ${variable_label} 0} SPECIAL_expr} + } + } + } + } +} + +if [prepare_for_testing ${testfile}.exp ${executable} "${asm_file} ${srcfile}" {}] { + return -1 +} + +# DW_OP_GNU_implicit_pointer implementation requires a valid frame. +if ![runto_main] { + return -1 +} + +gdb_test "print ref" " = \\(int &\\) " "print ref" +gdb_test "print &ref" " = \\(int \\*\\) " "print &ref" + +# gdb assumes C++ references are implemented as pointers, and print &(&ref) +# shows us the underlying pointer's address. +# Since in this case there's no physical pointer, gdb should tell us so. +gdb_test "print &\(&ref\)" "Attempt to take address of value not located in memory." "print &(&ref)" diff --git a/gdb/valops.c b/gdb/valops.c index 5a244a9f63e..8a555f32868 100644 --- a/gdb/valops.c +++ b/gdb/valops.c @@ -1463,11 +1463,20 @@ value_addr (struct value *arg1) if (TYPE_CODE (type) == TYPE_CODE_REF) { /* Copy the value, but change the type from (T&) to (T*). We - keep the same location information, which is efficient, and - allows &(&X) to get the location containing the reference. */ + keep the same location information, which is efficient, and + allows &(&X) to get the location containing the reference. + Do the same to its enclosing type for consistency. */ + struct type *type_ptr + = lookup_pointer_type (TYPE_TARGET_TYPE (type)); + struct type *enclosing_type + = check_typedef (value_enclosing_type (arg1)); + struct type *enclosing_type_ptr + = lookup_pointer_type (TYPE_TARGET_TYPE (enclosing_type)); + arg2 = value_copy (arg1); - deprecated_set_value_type (arg2, - lookup_pointer_type (TYPE_TARGET_TYPE (type))); + deprecated_set_value_type (arg2, type_ptr); + set_value_enclosing_type (arg2, enclosing_type_ptr); + return arg2; } if (TYPE_CODE (type) == TYPE_CODE_FUNC)