[PING][PATCH][gdb/exp] Fix printing of type of optimized out vla

Tom de Vries
2018-07-13T06:16:54Z

On 07/03/2018 04:18 PM, Tom de Vries wrote:
> Hi,
>
> Consider this snippet from gcc/testsuite/gcc.dg/guality/vla-1.c:
> ...
> int __attribute__((noinline))
> f1 (int i)
> {
> char a[i + 1];
> a[0] = 5; /* { dg-final { gdb-test .+1 "i" "5" } } */
> return a[0]; /* { dg-final { gdb-test . "sizeof (a)" "6" } } */
> }
> ...
>
> When we compile the test-case with -O1 -g, and query the size of optimized
> out vla 'a', we get:
> ...
> $ ./gdb -batch -ex "b f1" -ex "r" -ex "p sizeof (a)" vla-1.exe
> Breakpoint 1 at 0x4004a8: file vla-1.c, line 17.
>
> Breakpoint 1, f1 (i=i@entry=5) at vla-1.c:17
> 17 return a[0];
> $1 = 0
> ...
> while we expect a size of '6'.
>
> The problem is that default_read_var_value does not resolve the dynamic type
> of a variable if the variable is optimized out.
>
> This patch fixes that, and consequently gdb prints '6', as expected.
>
> Tested on x86_64-linux.
>
> OK for trunk?
>
> Thanks,
> - Tom
>
> [gdb/exp] Fix printing of type of optimized out vla
>
> 2018-07-03 Tom de Vries <tdevries@suse.de>
>
> * findvar.c (default_read_var_value): Also resolve dynamic type for
> LOC_OPTIMIZED_OUT vars.
>
> * gdb.base/vla-optimized-out.c: New test.
> * gdb.base/vla-optimized-out.exp: New file.
>
> ---
> gdb/findvar.c | 2 ++
> gdb/testsuite/gdb.base/vla-optimized-out.c | 34 +++++++++++++++++++++++
> gdb/testsuite/gdb.base/vla-optimized-out.exp | 40 ++++++++++++++++++++++++++++
> 3 files changed, 76 insertions(+)
>
> diff --git a/gdb/findvar.c b/gdb/findvar.c
> index 8ad5e25cb2..ebaff923a1 100644
> --- a/gdb/findvar.c
> +++ b/gdb/findvar.c
> @@ -789,6 +789,8 @@ default_read_var_value (struct symbol *var, const struct block *var_block,
> break;
>
> case LOC_OPTIMIZED_OUT:
> + if (is_dynamic_type (type))
> + type = resolve_dynamic_type (type, NULL, /* Unused address. */ 0);
> return allocate_optimized_out_value (type);
>
> default:
> diff --git a/gdb/testsuite/gdb.base/vla-optimized-out.c b/gdb/testsuite/gdb.base/vla-optimized-out.c
> new file mode 100644
> index 0000000000..913e8ea867
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/vla-optimized-out.c
> @@ -0,0 +1,34 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> + Copyright 2018 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 __attribute__((noinline, noclone))
> +f1 (int i)
> +{
> + char a[i + 1];
> + a[0] = 5;
> + return a[0];
> +}
> +
> +int
> +main (void)
> +{
> + volatile int j;
> + int i = 5;
> + asm volatile ("" : "=r" (i) : "0" (i));
> + j = f1 (i);
> + return 0;
> +}
> diff --git a/gdb/testsuite/gdb.base/vla-optimized-out.exp b/gdb/testsuite/gdb.base/vla-optimized-out.exp
> new file mode 100644
> index 0000000000..39abb795c8
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/vla-optimized-out.exp
> @@ -0,0 +1,40 @@
> +# Copyright 2018 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/>.
> +
> +# Check whether we can determine the size of an optimized-out vla.
> +
> +standard_testfile
> +
> +if { [prepare_for_testing "failed to prepare" $testfile $srcfile \
> + {debug optimize=-O1}] } {
> + return -1
> +}
> +
> +proc vla_optimized_out { } {
> + if ![runto f1] {
> + fail "can't run to f1"
> + return
> + }
> +
> + gdb_test "p a" \
> + { = <optimized out>} \
> + "printed optimized out vla"
> +
> + gdb_test "p sizeof (a)" \
> + { = 6} \
> + "printed size of optimized out vla"
> +}
> +
> +vla_optimized_out
>