Fix error propagation from the Z0 packet in gdb-remote breakpoint setting.

The error was not getting propagated to the caller, so the higher layers thought the breakpoint
was successfully set & resolved.

I added a testcase, but it assumes 0x0 is not a valid place to set a breakpoint.  On most systems
that is true, but if it isn't true of your system, either find another good place and add it to the
test, or x-fail the test.

<rdar://problem/26345962>

llvm-svn: 270014

lldb/packages/Python/lldbsuite/test/functionalities/breakpoint/address_breakpoints/TestBadAddressBreakpoints.py

@@ -0,0 +1,77 @@
+"""
+Test that breakpoints set on a bad address say they are bad.
+"""
+
+from __future__ import print_function
+
+
+
+import os, time
+import re
+import lldb
+import lldbsuite.test.lldbutil as lldbutil
+from lldbsuite.test.lldbtest import *
+
+class BadAddressBreakpointTestCase(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    def test_bad_address_breakpoints (self):
+        """Test that breakpoints set on a bad address say they are bad."""
+        self.build()
+        self.address_breakpoints()
+
+    def setUp(self):
+        # Call super's setUp().
+        TestBase.setUp(self)
+
+    def address_breakpoints(self):
+        """Test that breakpoints set on a bad address say they are bad."""
+        exe = os.path.join(os.getcwd(), "a.out")
+
+        # Create a target by the debugger.
+        target = self.dbg.CreateTarget(exe)
+        self.assertTrue(target, VALID_TARGET)
+
+        # Now create a breakpoint on main.c by name 'c'.
+        breakpoint = target.BreakpointCreateBySourceRegex("Set a breakpoint here", lldb.SBFileSpec("main.c"))
+        self.assertTrue(breakpoint and
+                        breakpoint.GetNumLocations() == 1,
+                        VALID_BREAKPOINT)
+
+        # Get the breakpoint location from breakpoint after we verified that,
+        # indeed, it has one location.
+        location = breakpoint.GetLocationAtIndex(0)
+        self.assertTrue(location and
+                        location.IsEnabled(),
+                        VALID_BREAKPOINT_LOCATION)
+
+        launch_info = lldb.SBLaunchInfo(None)
+        
+        error = lldb.SBError()
+
+        process = target.Launch (launch_info, error)
+        self.assertTrue(process, PROCESS_IS_VALID)
+
+        # Did we hit our breakpoint?
+        from lldbsuite.test.lldbutil import get_threads_stopped_at_breakpoint 
+        threads = get_threads_stopped_at_breakpoint (process, breakpoint)
+        self.assertTrue(len(threads) == 1, "There should be a thread stopped at our breakpoint")
+
+        # The hit count for the breakpoint should be 1.
+        self.assertTrue(breakpoint.GetHitCount() == 1)
+
+        # Now see if we can read from 0.  If I can't do that, I don't have a good way to know
+        # what an illegal address is...
+        error.Clear()
+
+        ptr = process.ReadPointerFromMemory(0x0, error)
+
+        if not error.Success():
+            bkpt = target.BreakpointCreateByAddress(0x0)
+            for bp_loc in bkpt:
+                self.assertTrue(bp_loc.IsResolved() == False)
+        else:
+            self.fail("Could not find an illegal address at which to set a bad breakpoint.")
+            
+            

lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp

@@ -3307,7 +3307,8 @@ ProcessGDBRemote::EnableBreakpointSite (BreakpointSite *bp_site)
     if (m_gdb_comm.SupportsGDBStoppointPacket(eBreakpointSoftware) && (!bp_site->HardwareRequired()))
     {
         // Try to send off a software breakpoint packet ($Z0)
-        if (m_gdb_comm.SendGDBStoppointTypePacket(eBreakpointSoftware, true, addr, bp_op_size) == 0)
+        uint8_t error_no = m_gdb_comm.SendGDBStoppointTypePacket(eBreakpointSoftware, true, addr, bp_op_size);
+        if (error_no == 0)
         {
             // The breakpoint was placed successfully
             bp_site->SetEnabled(true);
@@ -3323,7 +3324,13 @@ ProcessGDBRemote::EnableBreakpointSite (BreakpointSite *bp_site)
         // with the error code.  If they are now unsupported, then we would like to fall through
         // and try another form of breakpoint.
         if (m_gdb_comm.SupportsGDBStoppointPacket(eBreakpointSoftware))
+        {
+            if (error_no != UINT8_MAX)
+                error.SetErrorStringWithFormat("error: %d sending the breakpoint request", errno);
+            else
+                error.SetErrorString("error sending the breakpoint request");
             return error;
+        }
 
         // We reach here when software breakpoints have been found to be unsupported. For future
         // calls to set a breakpoint, we will not attempt to set a breakpoint with a type that is
@@ -3340,7 +3347,8 @@ ProcessGDBRemote::EnableBreakpointSite (BreakpointSite *bp_site)
     if (m_gdb_comm.SupportsGDBStoppointPacket(eBreakpointHardware))
     {
         // Try to send off a hardware breakpoint packet ($Z1)
-        if (m_gdb_comm.SendGDBStoppointTypePacket(eBreakpointHardware, true, addr, bp_op_size) == 0)
+        uint8_t error_no = m_gdb_comm.SendGDBStoppointTypePacket(eBreakpointHardware, true, addr, bp_op_size);
+        if (error_no == 0)
         {
             // The breakpoint was placed successfully
             bp_site->SetEnabled(true);
@@ -3352,7 +3360,13 @@ ProcessGDBRemote::EnableBreakpointSite (BreakpointSite *bp_site)
         if (m_gdb_comm.SupportsGDBStoppointPacket(eBreakpointHardware))
         {
             // Unable to set this hardware breakpoint
-            error.SetErrorString("failed to set hardware breakpoint (hardware breakpoint resources might be exhausted or unavailable)");
+            if (error_no != UINT8_MAX)
+                error.SetErrorStringWithFormat("error: %d sending the hardware breakpoint request "
+                                               "(hardware breakpoint resources might be exhausted or unavailable)",
+                                               error_no);
+            else
+                error.SetErrorString("error sending the hardware breakpoint request (hardware breakpoint resources "
+                                     "might be exhausted or unavailable)");
             return error;
         }