Re: [patch] fix tkill_failed gcc warning in gdbserver

[Doug Evans <dje@google.com>]

On Mon, Dec 21, 2009 at 12:36 PM, Doug Evans <dje@google.com> wrote:
> On Mon, Dec 21, 2009 at 12:19 PM, Daniel Jacobowitz <drow@false.org> wrote:
>> On Mon, Dec 21, 2009 at 12:10:33PM -0800, Doug Evans wrote:
>>> Hi.
>>>
>>> android doesn't have SYS_tkill but it does have __NR_tkill.
>>
>> Does it have the other SYS_ constants?  It's a weird omission.
>> Anyway, might as well use __NR_tkill unconditionally.
>
> The next question is, does gdbserver need to check for
> syscall.h/syscall() like gdb does?
> Or can I just replace #ifdef SYS_tkill with #ifdef __NR_tkill.
> gdbserver includes sys/syscall.h unconditionally, gdb/linux-nat.c  does not.
> gdb also checks for __NR_tkill in a way that works if it were an enum.
> Does one need to worry about that case?
>

How about this?

2009-12-21  Doug Evans  <dje@google.com>

        gdb/
        * linux-nat.c (kill_lwp): Minor cleanup, move definition of
        tkill_failed into ifdef HAVE_TKILL_SYSCALL.  Move setting of errno
        there too.  Delete unnecessary resetting of errno after syscall.
	Minor comment changes to match gdbserver/linux-low.c:kill_lwp.

        gdbserver/
        * linux-low.c (kill_lwp): Use __NR_tkill instead of SYS_tkill.
        Move definition of tkill_failed to ifdef __NR_tkill to avoid gcc
        warning ifndef __NR_tkill.  Move setting of errno there too.
        Delete unnecessary resetting of errno after syscall.
        Minor comment changes to match gdb/linux-nat.c:kill_lwp.

Index: linux-nat.c
===================================================================
RCS file: /cvs/src/src/gdb/linux-nat.c,v
retrieving revision 1.156
diff -u -p -r1.156 linux-nat.c
--- linux-nat.c 20 Nov 2009 19:48:45 -0000      1.156
+++ linux-nat.c 21 Dec 2009 20:39:15 -0000
@@ -2034,27 +2034,29 @@ linux_nat_resume (struct target_ops *ops
     target_async (inferior_event_handler, 0);
 }

-/* Issue kill to specified lwp.  */
-
-static int tkill_failed;
+/* Send a signal to an LWP.  */

 static int
 kill_lwp (int lwpid, int signo)
 {
-  errno = 0;
-
-/* Use tkill, if possible, in case we are using nptl threads.  If tkill
-   fails, then we are not using nptl threads and we should be using kill.  */
+  /* Use tkill, if possible, in case we are using nptl threads.  If tkill
+     fails, then we are not using nptl threads and we should be using kill.  */

 #ifdef HAVE_TKILL_SYSCALL
-  if (!tkill_failed)
-    {
-      int ret = syscall (__NR_tkill, lwpid, signo);
-      if (errno != ENOSYS)
-       return ret;
-      errno = 0;
-      tkill_failed = 1;
-    }
+  {
+    static int tkill_failed;
+
+    if (!tkill_failed)
+      {
+       int ret;
+
+       errno = 0;
+       ret = syscall (__NR_tkill, lwpid, signo);
+       if (errno != ENOSYS)
+         return ret;
+       tkill_failed = 1;
+      }
+  }
 #endif

   return kill (lwpid, signo);
Index: gdbserver/linux-low.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/linux-low.c,v
retrieving revision 1.117
diff -u -p -r1.117 linux-low.c
--- gdbserver/linux-low.c       21 Dec 2009 17:54:03 -0000      1.117
+++ gdbserver/linux-low.c       21 Dec 2009 20:39:15 -0000
@@ -1572,25 +1584,29 @@ linux_wait (ptid_t ptid,

   return event_ptid;
 }

-/* Send a signal to an LWP.  For LinuxThreads, kill is enough; however, if
-   thread groups are in use, we need to use tkill.  */
+/* Send a signal to an LWP.  */

 static int
 kill_lwp (unsigned long lwpid, int signo)
 {
-  static int tkill_failed;
+  /* Use tkill, if possible, in case we are using nptl threads.  If tkill
+     fails, then we are not using nptl threads and we should be using kill.  */

-  errno = 0;
+#ifdef __NR_tkill
+  {
+    static int tkill_failed;

-#ifdef SYS_tkill
-  if (!tkill_failed)
-    {
-      int ret = syscall (SYS_tkill, lwpid, signo);
-      if (errno != ENOSYS)
-       return ret;
-      errno = 0;
-      tkill_failed = 1;
-    }
+    if (!tkill_failed)
+      {
+       int ret;
+
+       errno = 0;
+       ret = syscall (__NR_tkill, lwpid, signo);
+       if (errno != ENOSYS)
+         return ret;
+       tkill_failed = 1;
+      }
+  }
 #endif

   return kill (lwpid, signo);