1 # Copyright 2002, 2004, 2007-2012 Free Software Foundation, Inc.
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.
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.
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/>.
17 if { [skip_cplus_tests] } { continue }
20 set binfile ${objdir}/${subdir}/${testfile}
22 foreach file {hang1 hang2 hang3} {
23 if {[gdb_compile "${srcdir}/${subdir}/${file}.cc" "${file}.o" object {c++ debug}] != ""} {
29 if {[gdb_compile "hang1.o hang2.o hang3.o" ${binfile} executable {c++ debug}] != "" } {
37 gdb_reinitialize_dir $srcdir/$subdir
41 # As of May 1, 2002, GDB hangs trying to read the debug info for the
42 # `hang2.o' compilation unit from the executable `hang', when compiled
43 # by g++ 2.96 with STABS debugging info. Here's what's going on, as
46 # The definition of `struct A' in `hang.H' refers to `struct B' as an
47 # incomplete type. The stabs declare type number (1,3) to be a cross-
48 # reference type, `xsB:'.
50 # The definition of `struct C' contains a nested definition for
51 # `struct B' --- or more properly, `struct C::B'. However, the stabs
52 # fail to qualify the structure tag: it just looks like a definition
53 # for `struct B'. I think this is a compiler bug, but perhaps GCC
54 # doesn't emit qualified names for a reason.
56 # `hang.H' gets #included by both `hang1.C' and `hang2.C'. So the
57 # stabs for `struct A', the incomplete `struct B', and `struct C'
58 # appear in both hang1.o's and hang2.o's stabs.
60 # When those two files are linked together, since hang2.o appears
61 # later in the command line, its #inclusion of `hang.H' gets replaced
62 # with an N_EXCL stab, referring back to hang1.o's stabs for the
65 # When GDB builds psymtabs for the executable hang, it notes that
66 # hang2.o's stabs contain an N_EXCL referring to a header that appears
67 # in full in hang1.o's stabs. So hang2.o's psymtab lists a dependency
68 # on hang1.o's psymtab.
70 # When the user types the command `print var_in_b', GDB scans the
71 # psymtabs for a symbol by that name, and decides to read full symbols
74 # Since `hang2.o''s psymtab lists `hang1.o' as a dependency, GDB first
75 # reads `hang1.o''s symbols. When GDB sees `(1,3)=xsB:', it creates a
76 # type object for `struct B', sets its TYPE_FLAG_STUB flag, and
77 # records it as type number `(1,3)'.
79 # When GDB finds the definition of `struct C::B', since the stabs
80 # don't indicate that the type is nested within C, it treats it as
81 # a definition of `struct B'.
83 # When GDB is finished reading `hang1.o''s symbols, it calls
84 # `cleanup_undefined_types'. This function mistakes the definition of
85 # `struct C::B' for a definition for `struct B', and overwrites the
86 # incomplete type object for the real `struct B', using `memcpy'. Now
87 # stabs type number `(1,3)' refers to this (incorrect) complete type.
88 # Furthermore, the `memcpy' simply copies the original's `cv_type'
89 # field to the target, giving the target a corrupt `cv_type' ring: the
90 # chain does not point back to the target type.
92 # Having satisfied `hang2.o''s psymtab's dependencies, GDB begins to
93 # read `hang2.o''s symbols. These contain the true definition for
94 # `struct B', which refers to type number `(1,3)' as the type it's
95 # defining. GDB looks up type `(1,3)', and finds the (incorrect)
96 # complete type established by the call to `cleanup_undefined_types'
97 # above. However, it doesn't notice that the type is already defined,
98 # and passes it to `read_struct_type', which then writes the new
99 # definition's size, field list, etc. into the type object which
100 # already has those fields initialized. Adding insult to injury,
101 # `read_struct_type' then calls `finish_cv_type'; since the `memcpy'
102 # in `cleanup_undefined_types' corrupted the target type's `cv_type'
103 # ring, `finish_cv_type' enters an infinite loop.
105 # This checks that GDB recognizes when a structure is about to be
106 # overwritten, and refuses, with a complaint.
107 gdb_test "print var_in_b" " = 1729" "doesn't overwrite struct type"
109 # This checks that cleanup_undefined_types doesn't create corrupt
110 # cv_type chains. Note that var_in_hang3 does need to be declared in
111 # a separate compilation unit, whose psymtab depends on hang1.o's
112 # psymtab. Otherwise, GDB won't call cleanup_undefined_types (as it
113 # finishes hang1.o's symbols) before it calls make_cv_type (while
114 # reading hang3.o's symbols).
116 # The bug only happens when you compile with -gstabs+; Otherwise, GCC
117 # won't include the `const' qualifier on `const_B_ptr' in `hang3.o''s
118 # STABS, so GDB won't try to create a const variant of the smashed
119 # struct type, and get caught by the corrupted cv_type chain.
120 gdb_test "print var_in_hang3" " = 42" "doesn't corrupt cv_type chain"