| # Copyright 2002, 2004, 2007 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 <http://www.gnu.org/licenses/>. |
| |
| 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" |