From eb7f1c487a7d496bf9f6443ab2dae90257a8398c Mon Sep 17 00:00:00 2001 From: Jim Blandy Date: Thu, 2 May 2002 07:03:53 +0000 Subject: [PATCH] * gdb.c++/hang1.C, gdb.c++/hang2.C, gdb.c++/hang.H, gdb.c++/hang.exp: New test. --- gdb/testsuite/ChangeLog | 5 ++ gdb/testsuite/gdb.c++/hang.H | 12 ++++ gdb/testsuite/gdb.c++/hang.exp | 113 +++++++++++++++++++++++++++++++++ gdb/testsuite/gdb.c++/hang1.C | 3 + gdb/testsuite/gdb.c++/hang2.C | 8 +++ 5 files changed, 141 insertions(+) create mode 100644 gdb/testsuite/gdb.c++/hang.H create mode 100644 gdb/testsuite/gdb.c++/hang.exp create mode 100644 gdb/testsuite/gdb.c++/hang1.C create mode 100644 gdb/testsuite/gdb.c++/hang2.C diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index 1936f2ea1a0..7e737a0ce90 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2002-05-01 Jim Blandy + + * gdb.c++/hang1.C, gdb.c++/hang2.C, gdb.c++/hang.H, + gdb.c++/hang.exp: New test. + 2002-05-01 Fred Fish * gdb.base/completion.exp: Handle completions of "./Make" for diff --git a/gdb/testsuite/gdb.c++/hang.H b/gdb/testsuite/gdb.c++/hang.H new file mode 100644 index 00000000000..26fec8792ad --- /dev/null +++ b/gdb/testsuite/gdb.c++/hang.H @@ -0,0 +1,12 @@ +struct A +{ + struct B *b_ptr_in_a; +}; + +struct C +{ + struct B + { + int member_of_B_in_C; + }; +}; diff --git a/gdb/testsuite/gdb.c++/hang.exp b/gdb/testsuite/gdb.c++/hang.exp new file mode 100644 index 00000000000..560b3d043f8 --- /dev/null +++ b/gdb/testsuite/gdb.c++/hang.exp @@ -0,0 +1,113 @@ +# Copyright (C) 2002 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 2 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, write to the Free Software +# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + +# Please email any bugs, comments, and/or additions to this file to: +# bug-gdb@prep.ai.mit.edu + +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}/${testfile} + +foreach file {hang1 hang2} { + if { [gdb_compile "${srcdir}/${subdir}/${file}.C" "${file}.o" object {debug c++}] != "" } { + gdb_suppress_entire_file "Testcase compile failed, so all tests in this file will automatically fail." + } +} + +if {[gdb_compile "hang1.o hang2.o" ${binfile} executable {debug c++}] != "" } { + gdb_suppress_entire_file "Testcase compile failed, so all tests in this file will automatically fail." +} + + +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. + +gdb_test "print var_in_b" " = 1729" "can read debug info" diff --git a/gdb/testsuite/gdb.c++/hang1.C b/gdb/testsuite/gdb.c++/hang1.C new file mode 100644 index 00000000000..4b04d77e68c --- /dev/null +++ b/gdb/testsuite/gdb.c++/hang1.C @@ -0,0 +1,3 @@ +#include "hang.H" + +int main (int argc, char **argv) { return 0; } diff --git a/gdb/testsuite/gdb.c++/hang2.C b/gdb/testsuite/gdb.c++/hang2.C new file mode 100644 index 00000000000..59732f87d63 --- /dev/null +++ b/gdb/testsuite/gdb.c++/hang2.C @@ -0,0 +1,8 @@ +#include "hang.H" + +struct B +{ + int member_of_B; +}; + +int var_in_b = 1729; -- 2.30.2