Index: lldb/trunk/test/expression_command/expr-in-syscall/Makefile
===================================================================
--- lldb/trunk/test/expression_command/expr-in-syscall/Makefile
+++ lldb/trunk/test/expression_command/expr-in-syscall/Makefile
@@ -0,0 +1,5 @@
+LEVEL = ../../make
+
+C_SOURCES := main.c
+
+include $(LEVEL)/Makefile.rules
Index: lldb/trunk/test/expression_command/expr-in-syscall/TestExpressionInSyscall.py
===================================================================
--- lldb/trunk/test/expression_command/expr-in-syscall/TestExpressionInSyscall.py
+++ lldb/trunk/test/expression_command/expr-in-syscall/TestExpressionInSyscall.py
@@ -0,0 +1,90 @@
+"""Test that we are able to evaluate expressions when the inferior is blocked in a syscall"""
+
+import os
+import unittest2
+import lldb
+from lldbtest import *
+import lldbutil
+
+
+class ExprSyscallTestCase(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    @skipUnlessDarwin
+    @dsym_test
+    def test_setpgid_with_dsym(self):
+        self.buildDsym()
+        self.expr_syscall()
+
+    @expectedFailureAll("llvm.org/pr23659", oslist=["linux"], archs=["i386", "x86_64"])
+    @dwarf_test
+    def test_setpgid_with_dwarf(self):
+        self.buildDwarf()
+        self.expr_syscall()
+
+    def expr_syscall(self):
+        exe = os.path.join(os.getcwd(), 'a.out')
+
+        # Create a target by the debugger.
+        target = self.dbg.CreateTarget(exe)
+        self.assertTrue(target, VALID_TARGET)
+
+        listener = lldb.SBListener("my listener")
+
+        # launch the inferior and don't wait for it to stop
+        self.dbg.SetAsync(True)
+        error = lldb.SBError()
+        process = target.Launch (listener,
+                None,      # argv
+                None,      # envp
+                None,      # stdin_path
+                None,      # stdout_path
+                None,      # stderr_path
+                None,      # working directory
+                0,         # launch flags
+                False,     # Stop at entry
+                error)     # error
+
+        self.assertTrue(process and process.IsValid(), PROCESS_IS_VALID)
+
+        event = lldb.SBEvent()
+
+        # Give the child enough time to reach the syscall,
+        # while clearing out all the pending events.
+        # The last WaitForEvent call will time out after 2 seconds.
+        while listener.WaitForEvent(2, event):
+            pass
+
+        # now the process should be running (blocked in the syscall)
+        self.assertEqual(process.GetState(), lldb.eStateRunning, "Process is running")
+
+        # send the process a signal
+        process.SendAsyncInterrupt()
+        while listener.WaitForEvent(1, event):
+            pass
+
+        # as a result the process should stop
+        # in all likelihood we have stopped in the middle of the sleep() syscall
+        self.assertEqual(process.GetState(), lldb.eStateStopped, PROCESS_STOPPED)
+        thread = process.GetSelectedThread()
+
+        # try evaluating a couple of expressions in this state
+        self.expect("expr release_flag = 1", substrs = [" = 1"])
+        self.expect("print (int)getpid()", substrs = [str(process.GetProcessID())])
+
+        # and run the process to completion
+        process.Continue()
+
+        # process all events
+        while listener.WaitForEvent(1, event):
+            pass
+
+        self.assertEqual(process.GetState(), lldb.eStateExited)
+        self.assertEqual(process.GetExitStatus(), 0)
+
+if __name__ == '__main__':
+    import atexit
+    lldb.SBDebugger.Initialize()
+    atexit.register(lambda: lldb.SBDebugger.Terminate())
+    unittest2.main()
Index: lldb/trunk/test/expression_command/expr-in-syscall/main.c
===================================================================
--- lldb/trunk/test/expression_command/expr-in-syscall/main.c
+++ lldb/trunk/test/expression_command/expr-in-syscall/main.c
@@ -0,0 +1,11 @@
+#include <unistd.h>
+
+volatile int release_flag = 0;
+
+int main(int argc, char const *argv[])
+{
+    while (! release_flag) // Wait for debugger to attach
+        sleep(3);
+
+    return 0;
+}