137 lines
4.8 KiB
Diff
137 lines
4.8 KiB
Diff
From FEDORA_PATCHES Mon Sep 17 00:00:00 2001
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From: Tom Tromey <tromey@adacore.com>
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Date: Fri, 24 Feb 2023 10:40:16 -0700
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Subject: gdb-rhbz2183595-rustc-inside_main.patch
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;; Backport "Fix crash in inside_main_func"
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;; (Tom Tromey, RHBZ 2183595)
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gdb 13.1 crashes while running the rust compiler's debugger tests.
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The crash has a number of causes.
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First, the rust compiler still uses the C++-like _Z mangling, but with
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its own twist -- some hex digits added to the end of a symbol. So,
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while gdb finds the correct name of "main":
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(top-gdb) p name
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$13 = 0x292e0c0 "rustc_gdb_1031745::main"
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It isn't found in the minsyms, because C++ demangling yields:
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[99] t 0x90c0 _ZN17rustc_gdb_10317454main17h5b5be7fe16a97225E section .text rustc_gdb_1031745::main::h5b5be7fe16a97225 zko06yobckx336v
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This could perhaps be fixed. I also filed a new PR to suggest
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preferring the linkage name of the main program.
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Next, the rust compiler emits both a DW_TAG_subprogram and a
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DW_TAG_namespace for "main". This happens because the file is named
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"main.rs" -- i.e., the bug is specific to the source file name. The
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crash also seems to require the nested function inside of 'main', at
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least for me. The namespace always is generated, but perhaps this
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changes the ordering in the DWARF.
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When inside_main_func looks up the main symbol, it finds the namespace
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symbol rather than the function. (I filed a bug about fixing gdb's
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symbol tables -- long overdue.)
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Meanwhile, as I think it's important to fix this crash sooner rather
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than later, this patch changes inside_main_func to check that the
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symbol that is found is LOC_BLOCK. This perhaps should have been done
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in the first place, anyway.
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Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30158
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diff --git a/gdb/frame.c b/gdb/frame.c
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--- a/gdb/frame.c
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+++ b/gdb/frame.c
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@@ -2453,6 +2453,14 @@ inside_main_func (frame_info_ptr this_frame)
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if (bs.symbol == nullptr)
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return false;
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+ /* We might have found some unrelated symbol. For example, the
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+ Rust compiler can emit both a subprogram and a namespace with
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+ the same name in the same scope; and due to how gdb's symbol
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+ tables currently work, we can't request the one we'd
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+ prefer. */
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+ if (bs.symbol->aclass () != LOC_BLOCK)
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+ return false;
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+
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const struct block *block = bs.symbol->value_block ();
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gdb_assert (block != nullptr);
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sym_addr = block->start ();
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diff --git a/gdb/testsuite/gdb.rust/main-crash.exp b/gdb/testsuite/gdb.rust/main-crash.exp
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new file mode 100644
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--- /dev/null
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+++ b/gdb/testsuite/gdb.rust/main-crash.exp
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@@ -0,0 +1,35 @@
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+# Copyright (C) 2023 Free Software Foundation, Inc.
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+
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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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+
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+# Regression test for a crash in inside_main_func.
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+
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+load_lib rust-support.exp
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+require allow_rust_tests
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+
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+standard_testfile main.rs
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+if {[prepare_for_testing "failed to prepare" $testfile $srcfile \
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+ {debug rust}]} {
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+ return -1
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+}
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+
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+set line [gdb_get_line_number "BREAK"]
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+# The bug was that this would crash.
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+if {![runto ${srcfile}:$line]} {
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+ untested "could not run to breakpoint"
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+ return -1
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+}
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+
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+# Test that gdb is alive.
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+gdb_test "print 23" " = 23"
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diff --git a/gdb/testsuite/gdb.rust/main.rs b/gdb/testsuite/gdb.rust/main.rs
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new file mode 100644
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--- /dev/null
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+++ b/gdb/testsuite/gdb.rust/main.rs
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@@ -0,0 +1,30 @@
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+// Copyright (C) 2016-2023 Free Software Foundation, Inc.
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+
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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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+
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+#![allow(dead_code)]
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+#![allow(unused_variables)]
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+#![allow(unused_assignments)]
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+
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+fn global_fn(x: u8) {
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+ // BREAK
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+}
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+
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+fn main() {
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+ fn nested(y: u8) {
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+ global_fn(y)
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+ }
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+
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+ nested(23);
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+}
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