[PATCH 4/5] Fix exit/signal code on Cygwin

[Pedro Alves <pedro@palves.net>]

I noticed that on native Cygwin, gdb.python/py-events.exp has this:

 [Thread 15952.0x534 (id 1) exited with code 12]
...
 Program terminated with signal SIGSYS, Bad system call.
 ...
 (gdb) FAIL: gdb.python/py-events.exp: Inferior 1 terminated.

The program exits with normal exit code 12, not a signal.  SIGSYS is
12.

Similarly, gdb.base/exitsignal.exp has this:

 continue
 Continuing.
 [Thread 15220.0x219c (id 1) exited with code 2816]
 [Thread 15220.0x3a50 (id 3) exited with code 2816]
 [Thread 15220.0x25a0 (id 4) exited with code 2816]
 [Inferior 1 (process 15220) exited with code 05400]
 (gdb) FAIL: gdb.base/exitsignal.exp: program terminated with SIGSEGV (the program exited)

Here, the program exits with SIGSEGV, not normal exit code 2816 (05400
in octal).

The problem is that gdb/windows-nat.c does not know about Cygwin's
exit codes as seen from the native Windows side.  Same for gdbserver's
win32-low.c.

This commit fixes it.  To avoid duplicating code, it adds a new
native_exit_code_to_target_status function in nat/windows-nat.c used
by both GDB and GDBserver, with the MinGW-specific logic added by
commit 559e7e5056 ("Improve process exit status macros on MinGW")
moved there too.

Change-Id: I5c4d9cd81209d46598575518ef2fd205d77f9b66
commit-id: 153617c2
---
 gdb/nat/windows-nat.c  | 42 ++++++++++++++++++++++++++++++++++++++++++
 gdb/nat/windows-nat.h  |  4 ++++
 gdb/windows-nat.c      | 14 ++------------
 gdbserver/win32-low.cc | 13 ++-----------
 4 files changed, 50 insertions(+), 23 deletions(-)

diff --git a/gdb/nat/windows-nat.c b/gdb/nat/windows-nat.c
index b093acda342..4c8c9ea32a8 100644
--- a/gdb/nat/windows-nat.c
+++ b/gdb/nat/windows-nat.c
@@ -18,6 +18,8 @@
 
 #include "nat/windows-nat.h"
 #include "gdbsupport/common-debug.h"
+#include "gdbsupport/gdb_signals.h"
+#include "gdbsupport/gdb_wait.h"
 #include "target/target.h"
 
 #undef GetModuleFileNameEx
@@ -694,6 +696,46 @@ windows_process_info::add_all_dlls ()
 
 /* See nat/windows-nat.h.  */
 
+target_waitstatus
+native_exit_code_to_target_status (DWORD exit_code)
+{
+  target_waitstatus tstatus;
+
+#ifdef __CYGWIN__
+  /* /usr/include/cygwin/wait.h explains that a wait status is 16
+     bits, and looks like:
+
+       "<1 byte info> <1 byte code>
+       <code> == 0, child has exited, info is the exit value
+       <code> == 1..7e, child has exited, code is the signal number.
+       <code> == 7f, child has stopped, info was the signal number.
+       <code> == 80, there was a core dump."
+
+     However, when passing the wait status to native ExitProcess as a
+     native exit code, cygwin1.dll swaps the <info>/<code> bytes.
+     Swap them back into a wait status here.  */
+  int wstatus = ((exit_code & 0xff) << 8) | ((exit_code >> 8) & 0xff);
+  if (!WIFSIGNALED (wstatus))
+    tstatus.set_exited (WEXITSTATUS (wstatus));
+  else
+    tstatus.set_signalled (gdb_signal_from_host (WTERMSIG (wstatus)));
+#else
+  /* If the exit status looks like a fatal exception, but we don't
+     recognize the exception's code, make the original exit status
+     value available, to avoid losing information.  */
+  int exit_signal
+    = WIFSIGNALED (exit_code) ? WTERMSIG (exit_code) : -1;
+  if (exit_signal == -1)
+    tstatus.set_exited (exit_code);
+  else
+    tstatus.set_signalled (gdb_signal_from_host (exit_signal));
+#endif
+
+  return tstatus;
+}
+
+/* See nat/windows-nat.h.  */
+
 std::string
 event_code_to_string (DWORD event_code)
 {
diff --git a/gdb/nat/windows-nat.h b/gdb/nat/windows-nat.h
index 52378765438..1cabe288cee 100644
--- a/gdb/nat/windows-nat.h
+++ b/gdb/nat/windows-nat.h
@@ -347,6 +347,10 @@ struct windows_process_info
   int get_exec_module_filename (char *exe_name_ret, size_t exe_name_max_len);
 };
 
+/* Convert a native ExitProcess exit code to a target wait status.  */
+
+extern target_waitstatus native_exit_code_to_target_status (DWORD exit_code);
+
 /* Return a string version of EVENT_CODE.  */
 
 extern std::string event_code_to_string (DWORD event_code);
diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index a284438bd36..54755a4c996 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -62,7 +62,6 @@
 #include "complaints.h"
 #include "gdbsupport/gdb_tilde_expand.h"
 #include "gdbsupport/pathstuff.h"
-#include "gdbsupport/gdb_wait.h"
 #include "gdbsupport/symbol.h"
 #include "inf-loop.h"
 
@@ -1610,17 +1609,8 @@ windows_nat_target::get_windows_debug_event
 	}
       else if (windows_process->saw_create == 1)
 	{
-	  DWORD exit_status = current_event->u.ExitProcess.dwExitCode;
-	  /* If the exit status looks like a fatal exception, but we
-	     don't recognize the exception's code, make the original
-	     exit status value available, to avoid losing
-	     information.  */
-	  int exit_signal
-	    = WIFSIGNALED (exit_status) ? WTERMSIG (exit_status) : -1;
-	  if (exit_signal == -1)
-	    ourstatus->set_exited (exit_status);
-	  else
-	    ourstatus->set_signalled (gdb_signal_from_host (exit_signal));
+	  DWORD exit_code = current_event->u.ExitProcess.dwExitCode;
+	  *ourstatus = native_exit_code_to_target_status (exit_code);
 
 	  thread_id = current_event->dwThreadId;
 
diff --git a/gdbserver/win32-low.cc b/gdbserver/win32-low.cc
index 6f1cf5ed025..23812c0689f 100644
--- a/gdbserver/win32-low.cc
+++ b/gdbserver/win32-low.cc
@@ -33,7 +33,6 @@
 #include <process.h>
 #include "gdbsupport/gdb_tilde_expand.h"
 #include "gdbsupport/common-inferior.h"
-#include "gdbsupport/gdb_wait.h"
 
 using namespace windows_nat;
 
@@ -1062,16 +1061,8 @@ get_child_debug_event (DWORD *continue_status,
 
     case EXIT_PROCESS_DEBUG_EVENT:
       {
-	DWORD exit_status = current_event->u.ExitProcess.dwExitCode;
-	/* If the exit status looks like a fatal exception, but we
-	   don't recognize the exception's code, make the original
-	   exit status value available, to avoid losing information.  */
-	int exit_signal
-	  = WIFSIGNALED (exit_status) ? WTERMSIG (exit_status) : -1;
-	if (exit_signal == -1)
-	  ourstatus->set_exited (exit_status);
-	else
-	  ourstatus->set_signalled (gdb_signal_from_host (exit_signal));
+	DWORD exit_code = current_event->u.ExitProcess.dwExitCode;
+	*ourstatus = native_exit_code_to_target_status (exit_code);
       }
       continue_last_debug_event (DBG_CONTINUE, debug_threads);
       break;
-- 
2.53.0