Subversion Repositories openrisc_2011-10-31

#   Copyright 2002, 2004, 2007, 2008 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 .

if $tracelevel then {

        strace $tracelevel

}

set prms_id 0

set bug_id 0

if { [skip_cplus_tests] } { continue }

set testfile hang

set binfile ${objdir}/${subdir}/${testfile}

foreach file {hang1 hang2 hang3} {

    if {[gdb_compile "${srcdir}/${subdir}/${file}.C" "${file}.o" object {c++ debug}] != ""} {

        untested hang.exp

        return -1

    }

}

if {[gdb_compile "hang1.o hang2.o hang3.o" ${binfile} executable {c++ debug}] != "" } {

     untested hang.exp

     return -1

}

gdb_exit

gdb_start

gdb_reinitialize_dir $srcdir/$subdir

gdb_load ${binfile}

# As of May 1, 2002, GDB hangs trying to read the debug info for the

# `hang2.o' compilation unit from the executable `hang', when compiled

# by g++ 2.96 with STABS debugging info.  Here's what's going on, as

# best as I can tell.

#

# The definition of `struct A' in `hang.H' refers to `struct B' as an

# incomplete type.  The stabs declare type number (1,3) to be a cross-

# reference type, `xsB:'.

#

# The definition of `struct C' contains a nested definition for

# `struct B' --- or more properly, `struct C::B'.  However, the stabs

# fail to qualify the structure tag: it just looks like a definition

# for `struct B'.  I think this is a compiler bug, but perhaps GCC

# doesn't emit qualified names for a reason.

#

# `hang.H' gets #included by both `hang1.C' and `hang2.C'.  So the

# stabs for `struct A', the incomplete `struct B', and `struct C'

# appear in both hang1.o's and hang2.o's stabs.

#

# When those two files are linked together, since hang2.o appears

# later in the command line, its #inclusion of `hang.H' gets replaced

# with an N_EXCL stab, referring back to hang1.o's stabs for the

# header file.

#

# When GDB builds psymtabs for the executable hang, it notes that

# hang2.o's stabs contain an N_EXCL referring to a header that appears

# in full in hang1.o's stabs.  So hang2.o's psymtab lists a dependency

# on hang1.o's psymtab.

#

# When the user types the command `print var_in_b', GDB scans the

# psymtabs for a symbol by that name, and decides to read full symbols

# for `hang2.o'.

#

# Since `hang2.o''s psymtab lists `hang1.o' as a dependency, GDB first

# reads `hang1.o''s symbols.  When GDB sees `(1,3)=xsB:', it creates a

# type object for `struct B', sets its TYPE_FLAG_STUB flag, and

# records it as type number `(1,3)'.

#

# When GDB finds the definition of `struct C::B', since the stabs

# don't indicate that the type is nested within C, it treats it as

# a definition of `struct B'.

#

# When GDB is finished reading `hang1.o''s symbols, it calls

# `cleanup_undefined_types'.  This function mistakes the definition of

# `struct C::B' for a definition for `struct B', and overwrites the

# incomplete type object for the real `struct B', using `memcpy'.  Now

# stabs type number `(1,3)' refers to this (incorrect) complete type.

# Furthermore, the `memcpy' simply copies the original's `cv_type'

# field to the target, giving the target a corrupt `cv_type' ring: the

# chain does not point back to the target type.

#

# Having satisfied `hang2.o''s psymtab's dependencies, GDB begins to

# read `hang2.o''s symbols.  These contain the true definition for

# `struct B', which refers to type number `(1,3)' as the type it's

# defining.  GDB looks up type `(1,3)', and finds the (incorrect)

# complete type established by the call to `cleanup_undefined_types'

# above.  However, it doesn't notice that the type is already defined,

# and passes it to `read_struct_type', which then writes the new

# definition's size, field list, etc. into the type object which

# already has those fields initialized.  Adding insult to injury,

# `read_struct_type' then calls `finish_cv_type'; since the `memcpy'

# in `cleanup_undefined_types' corrupted the target type's `cv_type'

# ring, `finish_cv_type' enters an infinite loop.

# This checks that GDB recognizes when a structure is about to be

# overwritten, and refuses, with a complaint.

gdb_test "print var_in_b" " = 1729" "doesn't overwrite struct type"

# This checks that cleanup_undefined_types doesn't create corrupt

# cv_type chains.  Note that var_in_hang3 does need to be declared in

# a separate compilation unit, whose psymtab depends on hang1.o's

# psymtab.  Otherwise, GDB won't call cleanup_undefined_types (as it

# finishes hang1.o's symbols) before it calls make_cv_type (while

# reading hang3.o's symbols).

#

# The bug only happens when you compile with -gstabs+; Otherwise, GCC

# won't include the `const' qualifier on `const_B_ptr' in `hang3.o''s

# STABS, so GDB won't try to create a const variant of the smashed

# struct type, and get caught by the corrupted cv_type chain.

gdb_test "print var_in_hang3" " = 42" "doesn't corrupt cv_type chain"