Re: [PATCH][gdb] Ensure listing of unused static var in info locals

[Andrew Burgess <andrew dot burgess at embecosm dot com>]

* Tom de Vries <tdevries@suse.de> [2020-02-24 12:58:18 +0100]:

> Hi,
> 
> Consider a test-case compiled with -g:
> ...
> int main (void) {
>   static int b = 2;
>   return 0;
> }
> ...
> 
> When running info locals in main, we get:
> ...
> (gdb) info locals
> No locals.
> ...
> 
> The info locals documentation states:
> ...
> Print the local variables of the selected frame, each on a separate line.
> These are all variables (declared either static or automatic) accessible at
> the point of execution of the selected frame.
> ...
> So, "info locals" should have printed static variable b.
> 
> The variable is present in dwarf info:
> ...
>  <2><14a>: Abbrev Number: 6 (DW_TAG_variable)
>     <14b>   DW_AT_name        : b
>     <153>   DW_AT_const_value : 2
> ...
> but instead of a location attribute, it has a const_value attribute, which
> causes the corresponding symbol to have LOC_CONST, which causes info locals to
> skip it.
> 
> Fix this by handling LOC_CONST in iterate_over_block_locals.
> 
> Build and reg-tested on x86_64-linux.
> 
> OK for trunk?
> 
> Thanks,
> - Tom
> 
> [gdb] Ensure listing of unused static var in info locals
> 
> gdb/ChangeLog:
> 
> 2020-02-24  Tom de Vries  <tdevries@suse.de>
> 
> 	PR gdb/25592
> 	* stack.c (iterate_over_block_locals): Handle LOC_CONST.
> 
> gdb/testsuite/ChangeLog:
> 
> 2020-02-24  Tom de Vries  <tdevries@suse.de>
> 
> 	PR gdb/25592
> 	* gdb.base/info-locals-unused-static-var.c: New test.
> 	* gdb.base/info-locals-unused-static-var.exp: New file.

LGTM.

Thanks,
Andrew



> 
> ---
>  gdb/stack.c                                        |  1 +
>  .../gdb.base/info-locals-unused-static-var.c       | 24 +++++++++++++
>  .../gdb.base/info-locals-unused-static-var.exp     | 40 ++++++++++++++++++++++
>  3 files changed, 65 insertions(+)
> 
> diff --git a/gdb/stack.c b/gdb/stack.c
> index af30405f29..266d771e35 100644
> --- a/gdb/stack.c
> +++ b/gdb/stack.c
> @@ -2237,6 +2237,7 @@ iterate_over_block_locals (const struct block *b,
>      {
>        switch (SYMBOL_CLASS (sym))
>  	{
> +	case LOC_CONST:
>  	case LOC_LOCAL:
>  	case LOC_REGISTER:
>  	case LOC_STATIC:
> diff --git a/gdb/testsuite/gdb.base/info-locals-unused-static-var.c b/gdb/testsuite/gdb.base/info-locals-unused-static-var.c
> new file mode 100644
> index 0000000000..86d34b3579
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/info-locals-unused-static-var.c
> @@ -0,0 +1,24 @@
> +/* 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/>.  */
> +
> +int
> +main (void)
> +{
> +  static int b = 2;
> +
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.base/info-locals-unused-static-var.exp b/gdb/testsuite/gdb.base/info-locals-unused-static-var.exp
> new file mode 100644
> index 0000000000..79f02c25e6
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/info-locals-unused-static-var.exp
> @@ -0,0 +1,40 @@
> +# 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/>.  */
> +
> +# Test if an unused static local var is listed with info locals.
> +#
> +# Note: with gcc 4.8.5, we have:
> +# ...
> +# (gdb) info addr b
> +# Symbol "b" is static storage at address $hex
> +# ...
> +# but with gcc 7.5.0, we have instead:
> +# ...
> +# (gdb) info addr b
> +# Symbol "b" is constant.
> +# ...
> +
> +standard_testfile
> +
> +if {[prepare_for_testing "failed to prepare" $testfile $srcfile debug]} {
> +    return -1
> +}
> +
> +if ![runto_main] then {
> +    fail "can't run to main"
> +    return 0
> +}
> +
> +gdb_test "info locals" "\r\nb = .*"