From patchwork Fri Oct 27 02:38:33 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Simon Marchi X-Patchwork-Id: 23898 Received: (qmail 1021 invoked by alias); 27 Oct 2017 02:39:04 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Delivered-To: mailing list gdb-patches@sourceware.org Received: (qmail 999 invoked by uid 89); 27 Oct 2017 02:39:02 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-26.9 required=5.0 tests=BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3 autolearn=ham version=3.3.2 spammy=H*RU:193.180.251.45, Hx-spam-relays-external:193.180.251.45 X-HELO: sessmg23.ericsson.net Received: from sessmg23.ericsson.net (HELO sessmg23.ericsson.net) (193.180.251.45) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Fri, 27 Oct 2017 02:38:51 +0000 Received: from ESESSHC002.ericsson.se (Unknown_Domain [153.88.183.24]) by sessmg23.ericsson.net (Symantec Mail Security) with SMTP id D3.FD.09869.83C92F95; Fri, 27 Oct 2017 04:38:48 +0200 (CEST) Received: from EUR03-DB5-obe.outbound.protection.outlook.com (153.88.183.145) by oa.msg.ericsson.com (153.88.183.24) with Microsoft SMTP Server (TLS) id 14.3.352.0; Fri, 27 Oct 2017 04:38:48 +0200 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=simon.marchi@ericsson.com; Received: from elxacz23q12.localdomain (70.81.137.44) by AMSPR07MB312.eurprd07.prod.outlook.com (2a01:111:e400:802f::24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P256) id 15.20.178.3; Fri, 27 Oct 2017 02:38:45 +0000 From: Simon Marchi To: CC: Patrick Frants Subject: [pushed] Fix broken recursion detection when printing static members Date: Thu, 26 Oct 2017 22:38:33 -0400 Message-ID: <1509071913-4983-1-git-send-email-simon.marchi@ericsson.com> In-Reply-To: <20171025070820.5004-1-osscontribute@gmail.com> References: <20171025070820.5004-1-osscontribute@gmail.com> MIME-Version: 1.0 X-ClientProxiedBy: SN4PR0201CA0053.namprd02.prod.outlook.com (2603:10b6:803:20::15) To AMSPR07MB312.eurprd07.prod.outlook.com (2a01:111:e400:802f::24) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 0cb2fcac-7715-4b6f-0cfc-08d51ce3d904 X-Microsoft-Antispam: UriScan:; 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This is small enough that it doesn't require a copyright assignment. Thanks for reporting and fixing the bug! Actual commit: Recursion detection for static members was broken. The implementation uses a growing (and shrinking) obstack object to simulate a stack of addresses (CORE_ADDR). Pushing addresses is implemented by calling obstack_grow(), while popping is implemented by calling obstack_free(). The latter is problematic because obstack_free() expects a pointer to the base of an object. When popping elements of the stack however, obstack_free() was called with the new top, which potentially is not the same as the base of the stack. This is unintended use and the effect is that obstack->next_free and obstack->object_base members are assigned the value of the new top, which equals an empty stack. Summary: popping elements would always result in an empty stack, which breaks the recursion detection. The fix shrinks the stack using obstack_blank_fast() with a negative value as described at the bottom of this page: https://gcc.gnu.org/onlinedocs/libiberty/Extra-Fast-Growing.html "You can use obstack_blank_fast with a “negative” size argument to make the current object smaller. Just don’t try to shrink it beyond zero length—there’s no telling what will happen if you do that. Earlier versions of obstacks allowed you to use obstack_blank to shrink objects. This will no longer work." The reproducer is added to gdb.cp/classes.exp, which fails without this patch. gdb/ChangeLog: * cp-valprint.c (cp_print_value_fields): Use obstack_blank_fast to rewind obstack. gdb/testsuite/ChangeLog: * gdb.cp/classes.exp (test_static_members): Test printing Outer::instance. * gdb.cp/classes.c (struct Inner, struct Outer): New. (Inner::instance, Outer::instance): New. --- gdb/ChangeLog | 5 +++++ gdb/cp-valprint.c | 10 +++------- gdb/testsuite/ChangeLog | 7 +++++++ gdb/testsuite/gdb.cp/classes.cc | 13 +++++++++++++ gdb/testsuite/gdb.cp/classes.exp | 5 +++++ 5 files changed, 33 insertions(+), 7 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index caa6484..1d18881 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2017-10-26 Patrick Frants + + * cp-valprint.c (cp_print_value_fields): Use obstack_blank_fast + to rewind obstack. + 2017-10-26 Pedro Alves * remote.c (remote_async_terminal_ours_p): Delete. diff --git a/gdb/cp-valprint.c b/gdb/cp-valprint.c index fb9bfd9..609dabb 100644 --- a/gdb/cp-valprint.c +++ b/gdb/cp-valprint.c @@ -371,13 +371,9 @@ cp_print_value_fields (struct type *type, struct type *real_type, if (obstack_final_size > statmem_obstack_initial_size) { /* In effect, a pop of the printed-statics stack. */ - - void *free_to_ptr = - (char *) obstack_next_free (&dont_print_statmem_obstack) - - (obstack_final_size - statmem_obstack_initial_size); - - obstack_free (&dont_print_statmem_obstack, - free_to_ptr); + size_t shrink_bytes + = statmem_obstack_initial_size - obstack_final_size; + obstack_blank_fast (&dont_print_statmem_obstack, shrink_bytes); } if (last_set_recurse != recurse) diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index 0c6c93a..0e2bc23 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,10 @@ +2017-10-26 Patrick Frants + + * gdb.cp/classes.exp (test_static_members): Test printing + Outer::instance. + * gdb.cp/classes.c (struct Inner, struct Outer): New. + (Inner::instance, Outer::instance): New. + 2017-10-24 Pedro Alves * gdb.base/new-ui.exp (do_test): Split "delete all breakpoints on diff --git a/gdb/testsuite/gdb.cp/classes.cc b/gdb/testsuite/gdb.cp/classes.cc index 50f0740..a650846 100644 --- a/gdb/testsuite/gdb.cp/classes.cc +++ b/gdb/testsuite/gdb.cp/classes.cc @@ -665,6 +665,19 @@ void use_methods () base1 b (3); } +struct Inner +{ + static Inner instance; +}; + +struct Outer +{ + Inner inner; + static Outer instance; +}; + +Inner Inner::instance; +Outer Outer::instance; int main() diff --git a/gdb/testsuite/gdb.cp/classes.exp b/gdb/testsuite/gdb.cp/classes.exp index 9e2630a..374b632 100644 --- a/gdb/testsuite/gdb.cp/classes.exp +++ b/gdb/testsuite/gdb.cp/classes.exp @@ -602,6 +602,11 @@ proc test_static_members {} { gdb_test "print cnsi" \ "{x = 30, y = 40, static null = {x = 0, y = 0, static null = , static yy = {z = 5, static xx = {x = 1, y = 2, static null = , static yy = }}}, static yy = }" \ "print cnsi with static members" + + # Another case of infinite recursion. + gdb_test "print Outer::instance" \ + "{inner = {static instance = {static instance = }}, static instance = {inner = {static instance = {static instance = }}, static instance = }}" \ + "print recursive static member" } proc do_tests {} {