Fix windows-nat.c for -Wnarrowing

Sergio pointed out that the Windows builder was failing due to the
-Wnarrowing patch, with:

../../binutils-gdb/gdb/windows-nat.c:301:27: error: narrowing conversion of '3221225477' from 'DWORD {aka long unsigned int}' to 'int' inside { } [-Wnarrowing]
   {-1, GDB_SIGNAL_UNKNOWN}};
                           ^
../../binutils-gdb/gdb/windows-nat.c:301:27: error: narrowing conversion of '3221225725' from 'DWORD {aka long unsigned int}' to 'int' inside { } [-Wnarrowing]
../../binutils-gdb/gdb/windows-nat.c:301:27: error: narrowing conversion of '2147483651' from 'DWORD {aka long unsigned int}' to 'int' inside { } [-Wnarrowing]
../../binutils-gdb/gdb/windows-nat.c:301:27: error: narrowing conversion of '2147483652' from 'DWORD {aka long unsigned int}' to 'int' inside { } [-Wnarrowing]
../../binutils-gdb/gdb/windows-nat.c:301:27: error: narrowing conversion of '3221225614' from 'DWORD {aka long unsigned int}' to 'int' inside { } [-Wnarrowing]

Looking into this, I found two things.

First, in struct xlate_exception, it is better to have "them" be of
type DWORD, as that's the type actually in use.

Second, struct xlate_exception and xlate are not used in this file,
because the code in windows_nat_target::resume is #if'd out.

This patch changes the type of "them", but also similarly #if's out
this object.

In order to avoid a narrowing warning from the -1 entry, at Pedro's
suggestion I have removed this and changed windows_nat_target::resume
to use ranged for.

Tested by rebuilding using the mingw toolchain on x86-64 Fedora 28.  I
also tested it by temporarily removing the "#if 0"s and rebuilding.

gdb/ChangeLog
2018-08-29  Tom Tromey  <tom@tromey.com>

	* windows-nat.c (struct xlate_exception) <them>: Change type to
	DWORD.
	(xlate): Fix formatting.  Remove last entry.
	(struct xlate_exception, xlate): Comment out.
	(windows_nat_target::resume): Use ranged for.

1 files changed, 11 insertions, 9 deletions

diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index aea502638e0..da663496e5a 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -280,26 +280,29 @@ static const int *mappings;
    a segment register or not.  */
 static segment_register_p_ftype *segment_register_p;
 
+/* See windows_nat_target::resume to understand why this is commented
+   out.  */
+#if 0
 /* This vector maps the target's idea of an exception (extracted
    from the DEBUG_EVENT structure) to GDB's idea.  */
 
 struct xlate_exception
   {
-    int them;
+    DWORD them;
     enum gdb_signal us;
   };
 
-static const struct xlate_exception
-  xlate[] =
+static const struct xlate_exception xlate[] =
 {
   {EXCEPTION_ACCESS_VIOLATION, GDB_SIGNAL_SEGV},
   {STATUS_STACK_OVERFLOW, GDB_SIGNAL_SEGV},
   {EXCEPTION_BREAKPOINT, GDB_SIGNAL_TRAP},
   {DBG_CONTROL_C, GDB_SIGNAL_INT},
   {EXCEPTION_SINGLE_STEP, GDB_SIGNAL_TRAP},
-  {STATUS_FLOAT_DIVIDE_BY_ZERO, GDB_SIGNAL_FPE},
-  {-1, GDB_SIGNAL_UNKNOWN}};
+  {STATUS_FLOAT_DIVIDE_BY_ZERO, GDB_SIGNAL_FPE}
+};
 
+#endif /* 0 */
 
 struct windows_nat_target final : public x86_nat_target<inf_child_target>
 {
@@ -1408,12 +1411,11 @@ windows_nat_target::resume (ptid_t ptid, int step, enum gdb_signal sig)
   structure when passing the exception to the inferior.
   Note that this seems possible in the exception handler itself.  */
 	{
-	  int i;
-	  for (i = 0; xlate[i].them != -1; i++)
-	    if (xlate[i].us == sig)
+	  for (const xlate_exception &x : xlate)
+	    if (x.us == sig)
 	      {
 		current_event.u.Exception.ExceptionRecord.ExceptionCode
-		  = xlate[i].them;
+		  = x.them;
 		continue_status = DBG_EXCEPTION_NOT_HANDLED;
 		break;
 	      }