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[gdb/exp] Fix cast handling for indirection

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Consider a test-case compiled without debug info, containing:
...
char a = 'a';

char *
a_loc (void)
{
  return &a;
}
...

We get:
...
(gdb) p (char)*a_loc ()
Cannot access memory at address 0x10
...

There's a bug in unop_ind_base_operation::evaluate that evaluates
"(char)*a_loc ()" the same as:
...
(gdb) p (char)*(char)a_loc ()
Cannot access memory at address 0x10
...

Fix this by instead evaluating it the same as:
...
(gdb) p (char)*(char *)a_loc ()
$1 = 97 'a'
...

Tested on x86_64-linux.

PR exp/31693
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31693
This commit is contained in:
Tom de Vries
2024-05-03 09:37:19 +02:00
parent e6d60e7624
commit ed8fd0a342
3 changed files with 76 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
gdb/expop.h
View File

@@ -1513,9 +1513,11 @@ public:
struct expression *exp,
enum noside noside) override
{
if (expect_type != nullptr && expect_type->code () == TYPE_CODE_PTR)
expect_type = check_typedef (expect_type)->target_type ();
value *val = std::get<0> (m_storage)->evaluate (expect_type, exp, noside);
struct type *pointer_to_expect_type = (expect_type != nullptr
? lookup_pointer_type (expect_type)
: nullptr);
value *val
= std::get<0> (m_storage)->evaluate (pointer_to_expect_type, exp, noside);
return eval_op_ind (expect_type, exp, noside, val);
}

31
gdb/testsuite/gdb.base/cast-indirection.c Normal file
View File

@@ -0,0 +1,31 @@
/* This testcase is part of GDB, the GNU debugger.
Copyright 2024 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/>. */
char a = 'a';
char *
a_loc (void)
{
return &a;
}
int
main (void)
{
int res = *a_loc () == 'a';
return !res;
}

40
gdb/testsuite/gdb.base/cast-indirection.exp Normal file
View File

@@ -0,0 +1,40 @@
# Copyright (C) 2024 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 that "p (char)*a_loc ()" is handled as "p (char)*(char *)a_loc ()".
standard_testfile
if { [prepare_for_testing "failed to prepare" $testfile $srcfile \
{nodebug}] == -1} {
return -1
}
if ![runto_main] {
return -1
}
gdb_test "p a_loc ()" \
"'a_loc' has unknown return type; cast the call to its declared return type"
gdb_test "p *a_loc ()" \
"'a_loc' has unknown return type; cast the call to its declared return type"
gdb_test "p *(char *)a_loc ()" " = 97 'a'"
gdb_test "p (char)*(char *)a_loc ()" " = 97 'a'"
# Regression test for PR31693.
gdb_test "p (char)*a_loc ()" " = 97 'a'"