New testcase for PR tui/25126 (staled source cache)

I'm dealing with a Fedora GDB bug that is related to PR tui/25126, and
I thought I'd write a specific testcase for it because I couldn't find
one.

The idea is to get the simple reproducer from the bug and tweak the
testcase around it.  This one was a bit hard because, since we need to
modify the source file and recompile it, it involved a bit of TCL-foo
to do things.  Also for this reason, I'm only enabling the test for
native boards.

I tested this with an upstream GDB and made sure everything is
passing.  I also tested with a faulty GDB and made sure the test
failed.

gdb/testsuite/ChangeLog:
2020-02-11  Sergio Durigan Junior  <sergiodj@redhat.com>

	PR tui/25126
	https://bugzilla.redhat.com/show_bug.cgi?id=1784210
	* gdb.base/cached-source-file.c: New file.
	* gdb.base/cached-source-file.exp: New file.

Change-Id: Ib1b074342ebe8613c6d1dfde631691ebdf6d81c6

1 files changed, 43 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.base/cached-source-file.c b/gdb/testsuite/gdb.base/cached-source-file.c
new file mode 100644
index 0000000..6f62c29
--- /dev/null
+++ b/gdb/testsuite/gdb.base/cached-source-file.c
@@ -0,0 +1,43 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2020 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 for PR tui/25126.
+
+   The bug is about a regression that makes GDB not reload its source
+   code cache when the inferior's symbols are reloaded, which leads to
+   wrong backtraces/listings.
+
+   This bug is reproducible even without using the TUI.
+
+   The .exp testcase depends on the line numbers and contents from
+   this file  If you change this file, make sure to double-check the
+   testcase.  */
+
+#include <stdio.h>
+
+void
+foo (void)
+{
+  printf ("hello\n"); /* break-here */
+}
+
+int
+main ()
+{
+  foo ();
+  return 0;
+}