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5edbb6ed92
In commit ed8fd0a342 ("[gdb/exp] Fix cast handling for indirection"), I
introduced the behaviour that even though we have:
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(gdb) p *a_loc ()
'a_loc' has unknown return type; cast the call to its declared return type
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we get:
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(gdb) p (char)*a_loc ()
$1 = 97 'a'
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In other words, the unknown return type of a_loc is inferred from the cast,
effectually evaluating:
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(gdb) p (char)*(char *)a_loc ()
...
This is convient for the case that errno is defined as:
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#define errno (*__errno_location ())
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and the return type of __errno_location is unknown but the macro definition is
known, such that we can use:
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(gdb) p (int)errno
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instead of
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(gdb) p *(int *)__errno_location ()
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However, as Pedro has pointed out in post-commit review [1], this makes it
harder to reason about the semantics of an expression.
For instance, this:
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(gdb) p (long long)*a_loc ()"
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would be evaluated without debug info as:
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(gdb) p (long long)*(long long *)a_loc ()"
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but with debug info as:
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(gdb) p (long long)*(char *)a_loc ()"
...
Fix this by instead simply erroring out for this case:
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(gdb) p (char)*a_loc ()
'a_loc' has unknown return type; cast the call to its declared return type
...
Tested on x86_64-linux.
Approved-By: Pedro Alves <pedro@palves.net>
[1] https://sourceware.org/pipermail/gdb-patches/2024-May/208821.html
42 lines
1.3 KiB
Plaintext
42 lines
1.3 KiB
Plaintext
# Copyright (C) 2024 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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# Check that "p (char)*a_loc ()" is handled correctly.
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standard_testfile
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if { [prepare_for_testing "failed to prepare" $testfile $srcfile \
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{nodebug}] == -1} {
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return -1
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}
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if ![runto_main] {
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return -1
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}
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gdb_test "p a_loc ()" \
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"'a_loc' has unknown return type; cast the call to its declared return type"
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gdb_test "p *a_loc ()" \
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"'a_loc' has unknown return type; cast the call to its declared return type"
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gdb_test "p *(char *)a_loc ()" " = 97 'a'"
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gdb_test "p (char)*(char *)a_loc ()" " = 97 'a'"
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# Regression test for PR31693.
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gdb_test "p (char)*a_loc ()" \
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"'a_loc' has unknown return type; cast the call to its declared return type"
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