Re: [PATCH v2] Don't compare types of enum fields

[Simon Marchi via Gdb-patches <gdb-patches@sourceware.org>]

On 2020-12-17 2:29 p.m., Hannes Domani via Gdb-patches wrote:
> Comparing types of enum fields results in a crash, because they don't
> have a type.
> 
> It can be reproduced by comparing the types of 2 instances of the same
> enum type in different objects:
> 
> enum.h:
> enum e
> {
>   zero,
>   one,
> };
> 
> enum-1.c:
> int func();
> enum e e1;
> int main()
> {
>   return e1 + func();
> }
> 
> enum-2.c:
> enum e e2;
> int func()
> {
>   return e2;
> }
> 
> $ gcc -g -oenum enum-1.c enum-2.c
> $ gdb -q enum.exe
> Reading symbols from enum.exe...
> (gdb) py print(gdb.parse_and_eval("e1").type==gdb.parse_and_eval("e2").type)
> 
> Thread 1 received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 6184.0x1cc4]
> check_typedef (type=0x0) at C:/src/repos/binutils-gdb.git/gdb/gdbtypes.c:2745
> 2745      while (type->code () == TYPE_CODE_TYPEDEF)
> 
> gdb/ChangeLog:
> 
> 2020-12-17  Hannes Domani  <ssbssa@yahoo.de>
> 
> 	PR exp/27070
> 	* gdbtypes.c (check_types_equal): Don't compare types of enum fields.
> 
> gdb/testsuite/ChangeLog:
> 
> 2020-12-17  Hannes Domani  <ssbssa@yahoo.de>
> 
> 	PR exp/27070
> 	* gdb.base/pr27070-a.c: New test.
> 	* gdb.base/pr27070-b.c: New test.
> 	* gdb.base/pr27070.exp: New file.
> 	* gdb.base/pr27070.h: New test.
> ---
> v2:
> - Add detailed problem description in commit message and test case.

Same comment as Tom, please find a descriptive name for this test.

When you write the test, it's nice to name it after the PR number because
you don't have to think of a good name.  But that's about it, after that
it doesn't give a clue what the test is about.

> ---
>  gdb/gdbtypes.c                     |  4 +++-
>  gdb/testsuite/gdb.base/pr27070-a.c | 27 +++++++++++++++++++++++++++
>  gdb/testsuite/gdb.base/pr27070-b.c | 25 +++++++++++++++++++++++++
>  gdb/testsuite/gdb.base/pr27070.exp | 29 +++++++++++++++++++++++++++++
>  gdb/testsuite/gdb.base/pr27070.h   | 22 ++++++++++++++++++++++
>  5 files changed, 106 insertions(+), 1 deletion(-)
>  create mode 100644 gdb/testsuite/gdb.base/pr27070-a.c
>  create mode 100644 gdb/testsuite/gdb.base/pr27070-b.c
>  create mode 100644 gdb/testsuite/gdb.base/pr27070.exp
>  create mode 100644 gdb/testsuite/gdb.base/pr27070.h
> 
> diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c
> index a40ae5f30e..2207613eef 100644
> --- a/gdb/gdbtypes.c
> +++ b/gdb/gdbtypes.c
> @@ -4036,7 +4036,9 @@ check_types_equal (struct type *type1, struct type *type2,
>  	    case FIELD_LOC_KIND_ENUMVAL:
>  	      if (FIELD_ENUMVAL (*field1) != FIELD_ENUMVAL (*field2))
>  		return false;
> -	      break;
> +	      /* Don't compare types of enum fields, because they don't
> +		 have a type.  */
> +	      continue;
>  	    case FIELD_LOC_KIND_PHYSADDR:
>  	      if (FIELD_STATIC_PHYSADDR (*field1)
>  		  != FIELD_STATIC_PHYSADDR (*field2))
> diff --git a/gdb/testsuite/gdb.base/pr27070-a.c b/gdb/testsuite/gdb.base/pr27070-a.c
> new file mode 100644
> index 0000000000..f3850803ea
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/pr27070-a.c
> @@ -0,0 +1,27 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2020 Free Software Foundation, Inc.
> +
> +   This program is free software; you can redistribute it and/or modify
> +   it under the terms of the GNU General Public License as published by
> +   the Free Software Foundation; either version 3 of the License, or
> +   (at your option) any later version.
> +
> +   This program is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +   GNU General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +#include "pr27070.h"
> +
> +int func();
> +
> +enum e e1;
> +
> +int main()

int
main (void)

> +{
> +  return e1 + func();
> +}

Space before parens everywhere.

> diff --git a/gdb/testsuite/gdb.base/pr27070-b.c b/gdb/testsuite/gdb.base/pr27070-b.c
> new file mode 100644
> index 0000000000..39962c671a
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/pr27070-b.c
> @@ -0,0 +1,25 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2020 Free Software Foundation, Inc.
> +
> +   This program is free software; you can redistribute it and/or modify
> +   it under the terms of the GNU General Public License as published by
> +   the Free Software Foundation; either version 3 of the License, or
> +   (at your option) any later version.
> +
> +   This program is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +   GNU General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +#include "pr27070.h"
> +
> +enum e e2;
> +
> +int func()

int
func (void)

> +{
> +  return e2;
> +}

> diff --git a/gdb/testsuite/gdb.base/pr27070.exp b/gdb/testsuite/gdb.base/pr27070.exp
> new file mode 100644
> index 0000000000..3f565da661
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/pr27070.exp
> @@ -0,0 +1,29 @@
> +# Copyright 2020 Free Software Foundation, Inc.
> +
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +

Please add a short comment explaining what the test tests.  It's useful to refer
to the PR number in that comment, so readers can get more context if they want,
but don't just use "Test for PR 27070.", the comment needs to be informative even
if bugzilla disappears.

> +set testname pr27070
> +set sources "pr27070-a.c pr27070-b.c"

You can probably use:

standard_testfile -a.c -b.c

> +
> +if {[build_executable ${testname}.exp $testname $sources {debug}] == -1} {
> +    return -1
> +}
> +
> +# Start with a fresh gdb.
> +
> +clean_restart ${testname}

You can probably use "prepare_for_testing" which does the build_executable + clean_restart.

> +
> +if { [skip_python_tests] } { continue }

I suppose this can go earlier, to avoid compiling the program and starting GDB if
the test is going to be skipped anyway.

> +
> +gdb_test "py print(gdb.parse_and_eval('e1').type == gdb.parse_and_eval('e2').type)" "True"

I think it would make sense to move this test to the gdb.python directory.

Simon