Re: [PATCH 2/3] gdb: improve disassembler styling when Pygments raises an exception

[Tom de Vries <tdevries@suse.de>]

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On 10/10/22 13:16, Andrew Burgess wrote:
> Tom de Vries <tdevries@suse.de> writes:
> 
>> On 10/10/22 11:32, Andrew Burgess via Gdb-patches wrote:
>>> Simon Marchi <simark@simark.ca> writes:
>>>
>>>> On 2022-10-08 12:00, Andrew Burgess wrote:
>>>>> Simon Marchi <simark@simark.ca> writes:
>>>>>
>>>>>>> +# Check that, if the user is using Python Pygments for disassembler
>>>>>>> +# styling, then the styling correctly switches off when an error is
>>>>>>> +# detected in the Python code.
>>>>>>> +proc test_disassembler_error_handling { } {
>>>>>>> +
>>>>>>> +    # This test requires the Python Pygments module to be installed
>>>>>>> +    # and used by GDB.
>>>>>>> +    if { !$::python_disassembly_styling } {
>>>>>>> +	return
>>>>>>> +    }
>>>>>>> +
>>>>>>> +    save_vars { env(TERM) } {
>>>>>>> +	# We need an ANSI-capable terminal to get the output.
>>>>>>> +	setenv TERM ansi
>>>>>>> +
>>>>>>> +	# Restart GDB with the correct TERM variable setting, this
>>>>>>> +	# means that GDB will enable styling.
>>>>>>> +	clean_restart_and_disable "restart 4" $::binfile
>>>>>>> +
>>>>>>> +	# Disable use of libopcodes for styling.  As this function is
>>>>>>> +	# only called when Python Pygments module is available, we
>>>>>>> +	# should now be using that module to style the disassembler
>>>>>>> +	# output.
>>>>>>> +	gdb_test_no_output "maint set libopcodes-styling enabled off"
>>>>>>> +
>>>>>>> +	# Disassemble a single instruction and ensure that the output
>>>>>>> +	# has styling markers in it.
>>>>>>> +	set insn_before [get_single_disassembled_insn]
>>>>>>> +	gdb_assert { [regexp "\033" $insn_before] } \
>>>>>>> +	    "have style markers when Pygments is working fine"
>>>>>>> +
>>>>>>> +	# Now replace the standard function that colorizes the
>>>>>>> +	# disassembler output, with a new function that always returns
>>>>>>> +	# None, this should cause GDB to stop using the Pygments
>>>>>>> +	# module for disassembler styling.
>>>>>>> +	gdb_py_test_silent_cmd \
>>>>>>> +	    [multi_line_input \
>>>>>>> +		 "python" \
>>>>>>> +		 "def replacement_colorize_disasm(content,gdbarch):" \
>>>>>>> +		 "  return None" \
>>>>>>> +		 "gdb.styling.colorize_disasm = replacement_colorize_disasm" \
>>>>>>> +		 "\004"] \
>>>>>>
>>>>>> Any reason you are using \004 here, instead of end?  I don't quite
>>>>>> understand why, but it seems to cause some random failures.  Running the
>>>>>> test under `taskset -c 2` makes it fail most of the time.  Running it
>>>>>> with check-read1 makes it fail consistently:
>>>>>>
>>>>>>     FAIL: gdb.base/style.exp: capture_command_output for x/1i *main
>>>>>>
>>>>>> When changing \004 for end, it passes.  I don't have an explanation why
>>>>>> though.
>>>>>
>>>>> It'll be a copy&paste.  There's a couple of other places in the
>>>>> testsuite where this pattern is used.
>>>>>
>>>>> The patch below changes all three to use 'end'.  How's this?
>>>>>
>>>>> Thanks,
>>>>> Andrew
>>>>
>>>> This is fine with me, but again, I didn't dig into it so I don't really
>>>> know what sending a \004 was causing,
>>>
>>> Hi,
>>>
>>> Given you were seeing problems with the use of \004, and the tests
>>> definitely were not about whether \004 could be used or not, I've pushed
>>> the patch I proposed (exact version is below).
>>>
>>
>> I found this independently and filed a PR (
>> https://sourceware.org/bugzilla/show_bug.cgi?id=29664 ) and wrote the
>> same fix (in the same three test-cases), and was about to commit ...
>>
>> The FAIL is caused by using gdb_py_test_silent_cmd, which adds a "\n" at
>> the end of the command in combination with "\004", causing a stray "\n"
>> that generates an extra prompt, which makes the prompt matching
>> unpredictable.
> 
> Apologies for the duplicated effort.  Also, thanks for the explanation,
> which, if I'd spotted sooner would have saved me investigating the
> problem.
> 
> Again, thanks for picking up after me, and apologies for wasting your
> time.
> 

Hi Andrew,

thanks for following up.

Luckily most of my time went to investigating the root cause (which had 
me puzzled for quite a bit), so that's not effort wasted.

Also, I forgot to check the mailing list to see if the FAIL was already 
noted there, so that's on me.

Anyway, I propose to error out in gdb_test_multiple on this specific 
pattern.  Dealing with ^C / ^D for now.

Not tested yet (I'll start testing in now in combination with the 
proposed patch to fix the build).

WDYT?

Thanks,
- Tom

[-- Attachment #2: 0001-gdb-testsuite-Detect-trailing-C-D-in-command.patch --]
[-- Type: text/x-patch, Size: 2213 bytes --]

[gdb/testsuite] Detect trailing ^C/^D in command

Detect a trailing ^C/^D in the command argument of gdb_test, and error out.

Tested on x86_64-linux.

---
 gdb/testsuite/gdb.testsuite/gdb-test.exp | 34 ++++++++++++++++++++++++++------
 gdb/testsuite/lib/gdb.exp                |  4 ++++
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/gdb/testsuite/gdb.testsuite/gdb-test.exp b/gdb/testsuite/gdb.testsuite/gdb-test.exp
index 2ce8eb31d73..e891f81e7b0 100644
--- a/gdb/testsuite/gdb.testsuite/gdb-test.exp
+++ b/gdb/testsuite/gdb.testsuite/gdb-test.exp
@@ -19,10 +19,32 @@ clean_restart
 
 # Check that a command with trailing newline triggers an error.
 
-set results [catch {
-    gdb_test "pwd\n" ".*" "cmd with trailing newline"
-} output]
+with_test_prefix "cmd with trailing newline" {
+    set results [catch {
+	gdb_test "pwd\n" ".*" "pwd"
+    } output]
 
-gdb_assert { $results == 1 }
-set expected_error_msg "Invalid trailing newline in \"pwd\n\" command"
-gdb_assert { [string equal $output $expected_error_msg] }
+    gdb_assert { $results == 1 }
+    set expected_error_msg "Invalid trailing newline in \"pwd\n\" command"
+    gdb_assert { [string equal $output $expected_error_msg] }
+}
+
+with_test_prefix "cmd with trailing control code" {
+    foreach_with_prefix control_code {^C ^D} {
+	switch $control_code {
+	    ^C {
+		set cmd "\003"
+	    }
+	    ^D {
+		set cmd "\004"
+	    }
+	}
+	set results [catch {
+	    gdb_test $cmd ".*" "control code"
+	} output]
+
+	gdb_assert { $results == 1 }
+	set expected_error_msg "Invalid trailing control code in \"$cmd\" command"
+	gdb_assert { [string equal $output $expected_error_msg] }
+    }
+}
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 5f0acfaa530..ac28ede1b08 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -1003,6 +1003,10 @@ proc gdb_test_multiple { command message args } {
 	error "Invalid trailing newline in \"$command\" command"
     }
 
+    if [string match "*\[\003\004\]" $command] {
+	error "Invalid trailing control code in \"$command\" command"
+    }
+
     if [string match "*\[\r\n\]*" $message] {
 	error "Invalid newline in \"$message\" test"
     }