gdb: fix "list ." related crash

When a user attempts to use the "list ." command with an inferior that
doesn't have debug symbols, GDB would crash. This was reported as PR
gdb/31256.

The crash would happen when attempting to get the current symtab_and_line
for the stop location, because the symtab would return a null pointer
and we'd attempt to dereference it to print the line.

This commit fixes that by checking for an empty symtab and erroring out
of the function if it happens.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31256
Approved-By: Tom Tromey <tom@tromey.com>

diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
index c1c78344a7e7422765c516688ac58ccf1c8b9070..df11f956245c51efd35fffbb51c31133650ca001 100644 (file)
--- a/gdb/cli/cli-cmds.c
+++ b/gdb/cli/cli-cmds.c
@@ -1291,6 +1291,8 @@ list_command (const char *arg, int from_tty)
              set_default_source_symtab_and_line ();
              cursal = get_current_source_symtab_and_line ();
            }
+         if (cursal.symtab == nullptr)
+           error (_("No debug information available to print source lines."));
          list_around_line (arg, cursal);
          /* Set the repeat args so just pressing "enter" after using "list ."
             will print the following lines instead of the same lines again. */

diff --git a/gdb/testsuite/gdb.base/list-nodebug.c b/gdb/testsuite/gdb.base/list-nodebug.c
new file mode 100644 (file)
index 0000000..078517c
--- /dev/null
+++ b/gdb/testsuite/gdb.base/list-nodebug.c
@@ -0,0 +1,21 @@
+/* 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/>.  */
+
+int main ()
+{
+    return 0;
+}

diff --git a/gdb/testsuite/gdb.base/list-nodebug.exp b/gdb/testsuite/gdb.base/list-nodebug.exp
new file mode 100644 (file)
index 0000000..08de054
--- /dev/null
+++ b/gdb/testsuite/gdb.base/list-nodebug.exp
@@ -0,0 +1,37 @@
+# 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/>.
+
+# Test that using the command "list" in a file with no debug information
+# will not crash GDB and will give reasonable output.
+
+standard_testfile .c
+
+if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile} \
+    {nodebug}]} {
+    return -1
+}
+
+if {![runto_main]} {
+    untested "couldn't run to main"
+    return
+}
+
+# Check that GDB doesn't crash when we use list . on an inferior with
+# no debug information
+gdb_test "list ." "No debug.*" "first 'list .'"
+# This should be called twice because the first list invocation since
+# printing a frame may take a different codepath, which wouldn't
+# trigger the crash.
+gdb_test "list ." "No debug.*" "second 'list .'"