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

3 files changed, 148 insertions, 0 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index db85782..0682674 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+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.
+
 2020-02-11  Tom de Vries  <tdevries@suse.de>
 
 	PR testsuite/25488
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;
+}
diff --git a/gdb/testsuite/gdb.base/cached-source-file.exp b/gdb/testsuite/gdb.base/cached-source-file.exp
new file mode 100644
index 0000000..755416f
--- /dev/null
+++ b/gdb/testsuite/gdb.base/cached-source-file.exp
@@ -0,0 +1,98 @@
+# Copyright (C) 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.
+
+standard_testfile
+
+# Only run on native boards.
+if { [use_gdb_stub] || [target_info gdb_protocol] == "extended-remote" } {
+    return -1
+}
+
+# Because we need to modify the source file later, it's better if we
+# just copy it to our output directory (instead of messing with the
+# user's source directory).
+set newsrc [standard_output_file $testfile].c
+file copy -force -- $srcdir/$subdir/$srcfile $newsrc
+set srcfile $newsrc
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
+    return -1
+}
+
+# Get the line number for the line with the "break-here" marker.
+set bp_line [gdb_get_line_number "break-here" $srcfile]
+
+gdb_assert { [runto "$srcfile:$bp_line"] } \
+    "run to $srcfile:$bp_line"
+
+# Do a "list" and check that the printed line matches the line of the
+# original source file.
+gdb_test_no_output "set listsize 1"
+gdb_test "list" "$bp_line\[ \t\]+printf \\(\"hello\\\\n\"\\); /\\* break-here \\*/" \
+    "check the first version of the source file"
+
+# Modify the original source file, and add an extra line into it.
+# This only works locally because of the TCL commands.
+set bkpsrc [standard_output_file $testfile].c.bkp
+set bkpsrcfd [open $bkpsrc w]
+set srcfd [open $srcfile r]
+
+while { [gets $srcfd line] != -1 } {
+    if { [string first "break-here" $line] != -1 } {
+	# Put a "printf" line before the "break-here" line.
+	puts $bkpsrcfd "  printf (\"foo\\n\"); /* new-marker */"
+    }
+    puts $bkpsrcfd $line
+}
+
+close $bkpsrcfd
+close $srcfd
+file rename -force -- $bkpsrc $srcfile
+# We have to wait 1 second because of the way GDB checks whether the
+# binary has changed or not.  GDB uses stat(2) and currently checks
+# 'st_mtime', whose precision is measured in seconds.  Since the copy,
+# rename, and rebuild can take less than 1 second, GDB might mistakenly
+# assume that the binary is unchanged.
+sleep 1
+
+# Recompile the modified source.  We use "gdb_compile" here instead of
+# "prepare_for_testing" because we don't want to call "clean_restart".
+if { [gdb_compile "${srcfile}" "${binfile}" executable {debug}] != "" } {
+    return -1
+}
+
+# Rerun the program.  This should not only force GDB to reload the
+# source cache, but also to break at BP_LINE again, which now has
+# different contents.
+gdb_test_multiple "run" "rerun program" {
+    -re {The program being debugged has been started already\.\r\nStart it from the beginning\? \(y or n\) $} {
+	set binregex [string_to_regexp $binfile]
+	gdb_test "y" "\\`$binregex\\' has changed; re-reading symbols\.\r\nStarting program: ${binregex}.*" \
+	    "rerun program"
+    }
+}
+
+# Again, perform the listing and check that the line indeed has
+# changed for GDB.
+gdb_test "list" "${bp_line}\[ \t\]+printf \\(\"foo\\\\n\"\\); /\\\* new-marker \\\*/.*" \
+    "verify that the source code is properly reloaded"