Add test for following fork on position-independent executables

Commit

  b2e586e ("Defer breakpoint reset when cloning progspace for fork
  child")

fixed following fork childs when the executable is position-independent.
This patch adds a little test for it.

gdb/testsuite/ChangeLog:

	* gdb.base/pie-fork.c: New file.
	* gdb.base/pie-fork.exp: New file.

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2018-04-11  Simon Marchi  <simon.marchi@ericsson.com>
+
+	* gdb.base/pie-fork.c: New file.
+	* gdb.base/pie-fork.exp: New file.
+
 2018-04-11  Tom Tromey  <tom@tromey.com>
 
 	* gdb.rust/simple.exp: Add test for ".." struct initializer.

gdb/testsuite/gdb.base/pie-fork.c

@@ -0,0 +1,34 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2018 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/>.  */
+
+#include <unistd.h>
+
+static void
+break_here (void)
+{
+   int i;
+   for (i = 0; i < 30; i++)
+     sleep (1);
+}
+
+int
+main ()
+{
+  fork ();
+  break_here ();
+  return 0;
+}

gdb/testsuite/gdb.base/pie-fork.exp

@@ -0,0 +1,65 @@
+# Copyright 2018 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 we can follow forks properly when the executable is
+# position-independent.
+
+standard_testfile
+
+set opts [list debug additional_flags=-fPIE ldflags=-pie]
+
+if [prepare_for_testing "failed to prepare" $testfile $srcfile $opts] {
+    return
+}
+
+proc setup_test {detach_on_fork {follow_fork_mode "parent"}} {
+    global binfile
+
+    clean_restart ${binfile}
+
+    if ![runto_main] {
+	fail "can't run to main"
+	return
+    }
+
+    gdb_test_no_output "set detach-on-fork ${detach_on_fork}"
+    gdb_test_no_output "set follow-fork-mode ${follow_fork_mode}"
+
+    gdb_breakpoint "break_here"
+}
+
+proc_with_prefix test_detach_on_fork_follow_parent {} {
+    setup_test "on" "parent"
+
+    gdb_test "continue" "\r\nBreakpoint 2, break_here.*"
+}
+
+proc_with_prefix test_detach_on_fork_follow_child {} {
+    setup_test "on" "child"
+
+    gdb_test "continue" "\r\nThread 2.1 .* hit Breakpoint 2, break_here.*"
+}
+
+proc_with_prefix test_no_detach_on_fork {} {
+    setup_test "off"
+
+    gdb_test "continue" "\r\nThread 1.1 .* hit Breakpoint 2, break_here.*"
+    gdb_test "thread 2.1"
+    gdb_test "continue" "\r\nThread 2.1 .* hit Breakpoint 2, break_here.*"
+}
+
+test_detach_on_fork_follow_parent
+test_detach_on_fork_follow_child
+test_no_detach_on_fork