[binutils-gdb/gdb-7.11-branch] Fix cleanup in arm_linux_software_single_step

[Yao Qi <qiyao at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=523f1dab16b5c8706bbb81c6fdbac741b3fffb19

commit 523f1dab16b5c8706bbb81c6fdbac741b3fffb19
Author: Yao Qi <yao.qi@linaro.org>
Date:   Tue Feb 16 13:56:41 2016 +0000

    Fix cleanup in arm_linux_software_single_step
    
    I see the following error in testing aarch64 GDB debugging arm
    program.
    
    (gdb) PASS: gdb.reverse/readv-reverse.exp: set breakpoint at marker2
    continue
    Continuing.
    =================================================================
    ==32273==ERROR: AddressSanitizer: attempting free on address which was not malloc()-ed: 0x000000ce4c00 in thread T0
        #0 0x2ba5615645c7 in __interceptor_free (/usr/lib/x86_64-linux-gnu/libasan.so.1+0x545c7)^M
        #1 0x4be8b5 in VEC_CORE_ADDR_cleanup /home/yao/SourceCode/gnu/gdb/git/gdb/common/gdb_vecs.h:34^M
        #2 0x5e6d95 in do_my_cleanups /home/yao/SourceCode/gnu/gdb/git/gdb/common/cleanups.c:154^M
        #3 0x64c99a in fetch_inferior_event /home/yao/SourceCode/gnu/gdb/git/gdb/infrun.c:3975^M
        #4 0x678437 in inferior_event_handler /home/yao/SourceCode/gnu/gdb/git/gdb/inf-loop.c:44^M
        #5 0x5078f6 in remote_async_serial_handler /home/yao/SourceCode/gnu/gdb/git/gdb/remote.c:13223^M
        #6 0x4cecfd in run_async_handler_and_reschedule /home/yao/SourceCode/gnu/gdb/git/gdb/ser-base.c:137^M
        #7 0x676864 in gdb_wait_for_event /home/yao/SourceCode/gnu/gdb/git/gdb/event-loop.c:834^M
        #8 0x676a27 in gdb_do_one_event /home/yao/SourceCode/gnu/gdb/git/gdb/event-loop.c:323^M
        #9 0x676aed in start_event_loop /home/yao/SourceCode/gnu/gdb/git/gdb/event-loop.c:347^M
        #10 0x6706d2 in captured_command_loop /home/yao/SourceCode/gnu/gdb/git/gdb/main.c:318^M
        #11 0x66db8c in catch_errors /home/yao/SourceCode/gnu/gdb/git/gdb/exceptions.c:240^M
        #12 0x6716dd in captured_main /home/yao/SourceCode/gnu/gdb/git/gdb/main.c:1157^M
        #13 0x66db8c in catch_errors /home/yao/SourceCode/gnu/gdb/git/gdb/exceptions.c:240^M
        #14 0x671b7a in gdb_main /home/yao/SourceCode/gnu/gdb/git/gdb/main.c:1165^M
        #15 0x467684 in main /home/yao/SourceCode/gnu/gdb/git/gdb/gdb.c:32^M
        #16 0x2ba563ed7ec4 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21ec4)^M
        #17 0x4676b2 (/scratch/yao/gdb/build-git/aarch64-linux-gnu/gdb/gdb+0x4676b2)
    
    looks we should discard cleanup if function
    arm_linux_software_single_step returns early, or create cleanup when
    it is needed.
    
    gdb:
    
    2016-02-16  Yao Qi  <yao.qi@linaro.org>
    
    	* arm-linux-tdep.c (arm_linux_software_single_step): Assign
    	'old_chain' later.

Diff:
---
 gdb/ChangeLog        | 5 +++++
 gdb/arm-linux-tdep.c | 4 +++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 2f11ef5..0f57e38 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2016-02-16  Yao Qi  <yao.qi@linaro.org>
+
+	* arm-linux-tdep.c (arm_linux_software_single_step): Assign
+	'old_chain' later.
+
 2016-02-10  Joel Brobecker  <brobecker@adacore.com>
 
 	* version.in: Replace -cvs suffix by -git suffix.
diff --git a/gdb/arm-linux-tdep.c b/gdb/arm-linux-tdep.c
index 3421f3b..eba8604 100644
--- a/gdb/arm-linux-tdep.c
+++ b/gdb/arm-linux-tdep.c
@@ -933,13 +933,15 @@ arm_linux_software_single_step (struct frame_info *frame)
   CORE_ADDR pc;
   int i;
   VEC (CORE_ADDR) *next_pcs = NULL;
-  struct cleanup *old_chain = make_cleanup (VEC_cleanup (CORE_ADDR), &next_pcs);
+  struct cleanup *old_chain;
 
   /* If the target does have hardware single step, GDB doesn't have
      to bother software single step.  */
   if (target_can_do_single_step () == 1)
     return 0;
 
+  old_chain = make_cleanup (VEC_cleanup (CORE_ADDR), &next_pcs);
+
   arm_get_next_pcs_ctor (&next_pcs_ctx,
 			 &arm_linux_get_next_pcs_ops,
 			 gdbarch_byte_order (gdbarch),