Re: [PATCH][gdb/testsuite] Don't expect gdb_prompt in mi_skip_python_test

[Simon Marchi <simark@simark.ca>]

On 2019-07-27 1:52 p.m., Tom de Vries wrote:
> Hi,
> 
> During an openSUSE package build using 8.3 sources, I ran into this error
> with gdb.python/py-mi-events.exp:
> ...
> python print ('test')^M
> &"python print ('test')\n"^M
> ~"test\n"^M
> ^done^M
> (gdb) ^M
> python print (sys.version_info[0])^M
> &"python print (sys.version_info[0])\n"^M
> ~"3\n"^M
> ^done^M
> (gdb) FAIL: gdb.python/py-mi-events.exp: check if python 3
> ERROR: tcl error sourcing gdb-8.3/gdb/testsuite/gdb.python/py-mi-events.exp.
> ERROR: can't read "gdb_py_is_py3k": no such variable
>     while executing
> "if { $gdb_py_is_py3k == 0 } {
>         gdb_test_multiple "python print (sys.version_info\[1\])" \
> 	  "check if python 2.4" {
>             -re "\[45\].*$prompt_regex..."
>     (procedure "skip_python_tests_prompt" line 22)
>     invoked from within
> "skip_python_tests_prompt "$mi_gdb_prompt$""
>     (procedure "mi_skip_python_tests" line 3)
>     invoked from within
> ...
> 
> I managed to reproduce the error on 8.3 using a trigger patch:
> ...
> diff --git a/gdb/mi/mi-interp.c b/gdb/mi/mi-interp.c
> index 3e9f36897a..7be00ef9e8 100644
> --- a/gdb/mi/mi-interp.c
> +++ b/gdb/mi/mi-interp.c
> @@ -38,6 +38,7 @@
>  #include "cli-out.h"
>  #include "thread-fsm.h"
>  #include "cli/cli-interp.h"
> +#include "gdb_usleep.h"
> 
>  /* These are the interpreter setup, etc. functions for the MI
>     interpreter.  */
> @@ -96,7 +97,10 @@ display_mi_prompt (struct mi_interp *mi)
>  {
>    struct ui *ui = current_ui;
> 
> -  fputs_unfiltered ("(gdb) \n", mi->raw_stdout);
> +  fputs_unfiltered ("(gdb) ", mi->raw_stdout);
> +  gdb_flush (mi->raw_stdout);
> +  gdb_usleep (1000000);
> +  fputs_unfiltered ("\n", mi->raw_stdout);
>    gdb_flush (mi->raw_stdout);
>    ui->prompt_state = PROMPTED;
>  }
> ...
> 
> The error happens as follows.
> 
> On one hand, skip_python_tests_prompt uses the prompt_regexp parameter for the
> user_code argument of gdb_test_multiple:
> ...
> proc skip_python_tests_prompt { prompt_regexp } {
>     global gdb_py_is_py3k
> 
>     ...
> 
>     gdb_test_multiple "python print (sys.version_info\[0\])" "check if python 3" {
> 	-re "3.*$prompt_regexp" {
>             set gdb_py_is_py3k 1
>         }
> 	-re ".*$prompt_regexp" {
>             set gdb_py_is_py3k 0
>         }
>     }
> ...
> 
> On the otherhand, gdb_test_multiple itself uses $gdb_prompt:
> ...
>          -re "\r\n$gdb_prompt $" {
>             if ![string match "" $message] then {
>                 fail "$message"
>             }
>             set result 1
>         }
> ...
> 
> So when mi_skip_python_test calls skip_python_tests_prompt with prompt_regexp
> set to $mi_gdb_prompt:
> ...
> proc mi_skip_python_tests {} {
>     global mi_gdb_prompt
>     return [skip_python_tests_prompt "$mi_gdb_prompt$"]
> }
> ...
> and expect reads "(gdb) " (due to the trigger patch) and tries to match it,
> the user_code regexps using $prompt_regexp (set to $mi_gdb_prompt) don't match,
> but the $gdb_prompt regexp in gdb_test_multiple does match.
> 
> Fix this by adding a prompt_regexp parameter to gdb_test_multiple, and using the
> parameter in skip_python_tests_prompt.
> 
> Tested gdb.python/py-mi-events.exp in combination with trigger patch on
> x86_64-linux.
> 
> Tested on x86_64-linux.
> 
> OK for trunk?
> 
> [
> - There may be mi test-cases that use gdb_test_multiple that also need
>   fixing, but I'd rather get agreement on the fix first.
> - I initially tried to fix this by adding a gdb_test_multiple_prompt but I
>   didn't get that working.  I can post a follow-up patch doing the refactoring
>   for that if required, but I rather handle that in a separate patch, since
>   this seems to be non-trivial. ]

Hi Tom,

It seems like this failure is reproducible using "make check-read1".  If you haven't
seen that before, check it out in gdb/testsuite/README, I'm sure you'll find dozens
of other testsuite bugs with it :).

As for the issue itself, I guess the root problem is that we're using gdb_test_multiple, which
was meant for the CLI, in an MI setting.  I was afraid that the regexp made to match the various
errors, such as:

  -re "Undefined\[a-z\]* command:.*$gdb_prompt $"

wouldn't work in MI, but the way they are written, they should match this, for example:

  hello
  &"hello\n"
  &"Undefined command: \"hello\".  Try \"help\".\n"
  ^error,msg="Undefined command: \"hello\".  Try \"help\"."
  (gdb)

So the fix looks reasonable to me too (at least, I can't think of anything better at the moment).

Thanks,

Simon