[pushed] Fix "maintenance selftest" printing stray instructions (Re: [PATCH 4/6] Disassembly unit test: disassemble one instruction)

Pedro Alves
2017-02-02T23:39:54Z

On 02/02/2017 10:12 PM, Yao Qi wrote:
> On Thu, Feb 2, 2017 at 4:46 PM, Pedro Alves <palves@redhat.com> wrote:
>>
>> I'm not sure whether this was the reason for the unittest.exp
>> random failure, but I suspect so. (I failed to save the log,
>> and also forgot to check whether all selftests had passed.)
>>
>> The patchlet below fixes the spurious insn printing. OK?
>>
>
> Yes.
>

Alright, pushed, like this:

Subject: [PATCH] Fix "maintenance selftest" printing stray instructions

The "maintenance selftest" command is printing odd bits of stray
instructions like:

~~~
brkwarning: A handler for the OS ABI "GNU/Linux" is not built into this configuration
of GDB. Attempting to continue with the default HS settings.

brkmov r0, #0mov r0, #0mov r0, #0mov r0, #0mov r0, #0mov r0, #0mov r0, #0mov r0, #0mov r0, #0mov r0, #0mov r0, #0mov r0, #0mov r0, #0mov r0, #0mov r0, #0breakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakM3.L = 0xffff;/* ( -1) M3=0x0xffff(65535) */break 8break 8warning: A handler for the OS ABI "GNU/Linux" is not built into this configuration
of GDB. Attempting to continue with the default cris:common_v10_v32 settings.
~~~

etc. Those appear because here:

class gdb_disassembler_test : public gdb_disassembler
{
public:

const bool verbose = false;

explicit gdb_disassembler_test (struct gdbarch *gdbarch,
const gdb_byte *insn,
size_t len)
: gdb_disassembler (gdbarch,
(verbose ? gdb_stdout : &null_stream),
gdb_disassembler_test::read_memory),

specifically in this line:

(verbose ? gdb_stdout : &null_stream),

"verbose" has not been initialized yet, because the order of
initialization is base classes first, then members. I.e. "verbose" is
only initialized after the base constructor is called. Since the
gdb_disassembler_test object is created on the stack, "verbose" has
garbage at that point. If the gargage is non-zero, then we end up
with the gdb_disassembler_test's stream incorrectly pointing to
gdb_stdout.

gdb/ChangeLog:
2017-02-02 Pedro Alves <palves@redhat.com>

* disasm-selftests.c (print_one_insn_test): Move the "verbose"
field out of gdb_disassembler_test and make it static.
---
gdb/disasm-selftests.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/gdb/disasm-selftests.c b/gdb/disasm-selftests.c
index 7d0b006..9eb80b4 100644
--- a/gdb/disasm-selftests.c
+++ b/gdb/disasm-selftests.c
@@ -102,13 +102,12 @@ print_one_insn_test (struct gdbarch *gdbarch)
/* Test gdb_disassembler for a given gdbarch by reading data from a
pre-allocated buffer. If you want to see the disassembled
instruction printed to gdb_stdout, set verbose to true. */
+ static const bool verbose = false;

class gdb_disassembler_test : public gdb_disassembler
{
public:

- const bool verbose = false;
-
explicit gdb_disassembler_test (struct gdbarch *gdbarch,
const gdb_byte *insn,
size_t len)
--
2.5.5