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From: Tom de Vries <vries@sourceware.org> To: gdb-cvs@sourceware.org Subject: [binutils-gdb] [gdb/exp] Fix cast handling for indirection Date: Fri, 3 May 2024 07:36:58 +0000 (GMT) [thread overview] Message-ID: <20240503073658.1A50F384AB47@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=ed8fd0a342f6e832fee1a3fabc3e494977780dcf commit ed8fd0a342f6e832fee1a3fabc3e494977780dcf Author: Tom de Vries <tdevries@suse.de> Date: Fri May 3 09:37:19 2024 +0200 [gdb/exp] Fix cast handling for indirection 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 Diff: --- gdb/expop.h | 8 +++--- gdb/testsuite/gdb.base/cast-indirection.c | 31 ++++++++++++++++++++++ gdb/testsuite/gdb.base/cast-indirection.exp | 40 +++++++++++++++++++++++++++++ 3 files changed, 76 insertions(+), 3 deletions(-) diff --git a/gdb/expop.h b/gdb/expop.h index b81e228c07e..1967d9779b7 100644 --- a/gdb/expop.h +++ b/gdb/expop.h @@ -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); } diff --git a/gdb/testsuite/gdb.base/cast-indirection.c b/gdb/testsuite/gdb.base/cast-indirection.c new file mode 100644 index 00000000000..d59c66ead35 --- /dev/null +++ b/gdb/testsuite/gdb.base/cast-indirection.c @@ -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; +} diff --git a/gdb/testsuite/gdb.base/cast-indirection.exp b/gdb/testsuite/gdb.base/cast-indirection.exp new file mode 100644 index 00000000000..d2c6d58e3ca --- /dev/null +++ b/gdb/testsuite/gdb.base/cast-indirection.exp @@ -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'"
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