From 6a49a997b406fba3a389d9d8a6ff72042606c69d Mon Sep 17 00:00:00 2001 From: Yao Qi Date: Fri, 17 Jul 2015 12:14:59 +0100 Subject: [PATCH] Fix using uninitialised values We did a code refacotr here https://sourceware.org/ml/gdb-patches/2013-11/msg00063.html > (get_current_thread): New function, factored out from ... > (add_current_inferior_and_thread): ... this. Adjust. > >@@ -3332,18 +3371,8 @@ add_current_inferior_and_thread (char *wait_status) > > inferior_ptid = null_ptid; > >- /* Now, if we have thread information, update inferior_ptid. First >- if we have a stop reply handy, maybe it's a T stop reply with a >- "thread" register we can extract the current thread from. If >- not, ask the remote which is the current thread, with qC. The >- former method avoids a roundtrip. Note we don't use >- remote_parse_stop_reply as that makes use of the target >- architecture, which we haven't yet fully determined at this >- point. */ >- if (wait_status != NULL) >- ptid = stop_reply_extract_thread (wait_status); >- if (ptid_equal (ptid, null_ptid)) >- ptid = remote_current_thread (inferior_ptid); >+ /* Now, if we have thread information, update inferior_ptid. */ >+ ptid = get_current_thread (wait_status); but after the refactor, local variable ptid is used without initialisation. However, before this change, ptid is initialised to null_ptid. This error can be found by valgrind too... ==3298== at 0x6B99BA: ptid_equal (ptid.c:80) ==3298== by 0x4C67FF: get_current_thread (remote.c:3484) ==3298== by 0x4C6951: add_current_inferior_and_thread (remote.c:3511) ==3298== by 0x4C762C: extended_remote_create_inferior (remote.c:8506) ==3298== by 0x5A5312: run_command_1 (infcmd.c:606) ==3298== by 0x68B4FB: execute_command (top.c:463) ==3298== by 0x5C7214: command_handler (event-top.c:494) ==3298== by 0x5C78A3: command_line_handler (event-top.c:692) ==3298== by 0x6DEB57: rl_callback_read_char (callback.c:220) ==3298== by 0x5C7278: rl_callback_read_char_wrapper (event-top.c:171) ==3298== by 0x5C72C2: stdin_event_handler (event-top.c:432) ==3298== by 0x5C6194: gdb_wait_for_event (event-loop.c:834) This patch initialises local variable ptid to null in get_current_thread. We don't need to initialise ptid in add_current_inferior_and_thread, so this patch also removes the ptid initialisation. gdb: 2015-07-17 Yao Qi * remote.c (get_current_thread): Initialise ptid to null_ptid. (add_current_inferior_and_thread): Don't initialise ptid. --- gdb/ChangeLog | 5 +++++ gdb/remote.c | 4 ++-- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index f4857e3..646a827 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2015-07-17 Yao Qi + + * remote.c (get_current_thread): Initialise ptid to null_ptid. + (add_current_inferior_and_thread): Don't initialise ptid. + 2015-07-16 Pierre Langlois * aarch64-tdep.c (aarch64_pseudo_read_value): Mark S register as diff --git a/gdb/remote.c b/gdb/remote.c index 9d97f6b..94899bd 100644 --- a/gdb/remote.c +++ b/gdb/remote.c @@ -3474,7 +3474,7 @@ stop_reply_extract_thread (char *stop_reply) static ptid_t get_current_thread (char *wait_status) { - ptid_t ptid; + ptid_t ptid = null_ptid; /* Note we don't use remote_parse_stop_reply as that makes use of the target architecture, which we haven't yet fully determined at @@ -3503,7 +3503,7 @@ add_current_inferior_and_thread (char *wait_status) { struct remote_state *rs = get_remote_state (); int fake_pid_p = 0; - ptid_t ptid = null_ptid; + ptid_t ptid; inferior_ptid = null_ptid; -- 2.7.4