[gdb/exp] Fix ns var lookup when stopped at inlined fn call

Consider test.c:
...
     1	namespace mod_a {
     2	  int xxx = 10;
     3	}
     4
     5	static inline int __attribute__((always_inline))
     6	inlined () {
     7	  return 0;
     8	}
     9
    10	int main () {
    11	  using namespace mod_a;
    12	  int res = inlined ();
    13	  return res + xxx;
    14	}
...
compiled with "g++ test.c -g".

Trying to print variable xxx at line 12 fails:
...
$ gdb -q -batch a.out -ex start -ex "p xxx"
  ...
Temporary breakpoint 1, main () at test.c:12
12	  int res = inlined ();
No symbol "xxx" in current context.
...

The problem is here in function using_direct::valid_line:
...
      CORE_ADDR curr_pc = get_frame_pc (get_selected_frame (nullptr));
      symtab_and_line curr_sal = find_sal_for_pc (curr_pc, 0);
      return (decl_line <= curr_sal.line)
	     || (decl_line >= boundary);
...
where we're trying to decide whether "using namespace mod_a" is applicable.

The decl_line is 11, as expected.

If curr_sal.line were 12, decl_line <= curr_sal.line would be true, and
using_direct::valid_line would return true.

But instead, curr_sal.line is 7.

This is sort of correct, the current PC maps to that line.  It's just that gdb
steps into inlined functions in two steps, each with identical PC:
- once stopping at the call site (line 12 in this case)
- once stopping at the PC line (line 7 in this case)

The function using_direct::valid_line doesn't apply this logic, and
consequently line 7 is used for both cases.

Fix this by using find_frame_sal instead.

Tested on x86_64-linux.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=34201

gdb/namespace.c

@@ -111,8 +111,8 @@ using_direct::valid_line (unsigned int boundary) const
 {
   try
     {
-      CORE_ADDR curr_pc = get_frame_pc (get_selected_frame ());
-      symtab_and_line curr_sal = find_sal_for_pc (curr_pc, 0);
+      frame_info_ptr frame = get_selected_frame ();
+      symtab_and_line curr_sal = find_frame_sal (frame);
 
       /* Apply GCC PR debug/108716 workaround.  */
       if (boundary != 0

gdb/testsuite/gdb.cp/ns-inlined.c

@@ -0,0 +1,41 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2026 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/>.  */
+
+namespace mod_a
+{
+  int xxx = 10;
+}
+
+static inline int __attribute__((always_inline))
+inlined ()
+{
+  return 0;
+}
+
+static void
+foo ()
+{
+}
+
+int
+main ()
+{
+  foo ();                   /* stop 1.  */
+  using namespace mod_a;
+  int res = inlined ();     /* stop 2.  */
+  return res + xxx;         /* stop 3.  */
+}

gdb/testsuite/gdb.cp/ns-inlined.exp

@@ -0,0 +1,69 @@
+# Copyright 2026 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/>.
+
+standard_testfile .c
+
+set stop2_line [gdb_get_line_number "stop 2"]
+set stop3_line [gdb_get_line_number "stop 3"]
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile \
+	 {debug c++}]} {
+    return
+}
+
+if {![runto_main]} {
+    return
+}
+
+# Xfail for incorrect decl_line on DW_TAG_imported_module,
+# GCC PR debug/108716.
+set have_gcc108716_xfail \
+    [expr {[test_compiler_info gcc-*] && [gcc_major_version] < 13}]
+
+set re_pass [string_to_regexp {No symbol "xxx" in current context.}]
+set re_xfail "$valnum_re = 10"
+
+with_test_prefix "stop 1" {
+    gdb_test_multiple "print xxx" "" {
+	-re -wrap $re_pass {
+	    pass $gdb_test_name
+	}
+	-re -wrap $re_xfail {
+	    if {$have_gcc108716_xfail} {
+		setup_xfail *-*-* gcc/108716
+	    }
+	    fail $gdb_test_name
+	}
+    }
+}
+
+gdb_test "next" \
+    "\r\n$stop2_line\t\[^\r\n\]+" \
+    "next to stop 2"
+
+with_test_prefix "stop 2" {
+    # Regression test for PR exp/34201.
+    gdb_test "print xxx" \
+	"$valnum_re = 10"
+}
+
+gdb_test "next" \
+    "\r\n$stop3_line\t\[^\r\n\]+" \
+    "next to stop 3"
+
+with_test_prefix "stop 3" {
+    gdb_test "print xxx" \
+	"$valnum_re = 10"
+}