Improve process exit status macros on MinGW

When a Windows program is terminated by a fatal exception, its exit
code is the value of that exception, as defined by the various
EXCEPTION_* symbols in the Windows API headers.  This commit emulates
WTERMSIG etc. by translating the fatal exception codes to more-or-less
equivalent Posix signals.

gdb/ChangeLog:
2020-01-06  Eli Zaretskii  <eliz@gnu.org>
	    Pedro Alves  <palves@redhat.com>

	* Makefile.in (COMMON_SFILES): Add gdbsupport/gdb_wait.c.
	* windows-tdep.c: New enumeration of WINDOWS_SIG* signals.
	(windows_gdb_signal_to_target): New function, uses the above
	enumeration to convert GDB internal signal codes to equivalent
	Windows codes.
	(windows_init_abi): Call set_gdbarch_gdb_signal_to_target.
	* windows-nat.c: Include "gdb_wait.h".
	(get_windows_debug_event): Extract the fatal exception from the
	exit status and convert to the equivalent Posix signal number.
	* cli/cli-cmds.c (exit_status_set_internal_vars): Account for the
	possibility that WTERMSIG returns GDB_SIGNAL_UNKNOWN.
	* gdbsupport/gdb_wait.c: New file, implements
	windows_status_to_termsig.
	* gdbsupport/gdb_wait.h (WIFEXITED, WIFSIGNALED, WEXITSTATUS)
	(WTERMSIG) [__MINGW32__]: Separate definitions for MinGW.

gdb/gdbserver/ChangeLog:
2020-01-06  Eli Zaretskii  <eliz@gnu.org>
	    Pedro Alves  <palves@redhat.com>

	* win32-low.c (get_child_debug_event): Extract the fatal exception
	from the exit status and convert to the equivalent Posix signal
	number.
	(win32_wait): Allow TARGET_WAITKIND_SIGNALLED status as well.
	* Makefile.in (OBS, SFILES): Add gdb_wait.[co].

3 files changed, 31 insertions, 2 deletions

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 4d16083..63778e2 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,12 @@
+2020-01-06  Eli Zaretskii  <eliz@gnu.org>
+	    Pedro Alves  <palves@redhat.com>
+
+	* win32-low.c (get_child_debug_event): Extract the fatal exception
+	from the exit status and convert to the equivalent Posix signal
+	number.
+	(win32_wait): Allow TARGET_WAITKIND_SIGNALLED status as well.
+	* Makefile.in (OBS, SFILES): Add gdb_wait.[co].
+
 2020-01-01  Hannes Domani  <ssbssa@yahoo.de>
 
 	* Makefile.in: Use INSTALL_PROGRAM_ENV.
diff --git a/gdb/gdbserver/Makefile.in b/gdb/gdbserver/Makefile.in
index d39c065..1125426 100644
--- a/gdb/gdbserver/Makefile.in
+++ b/gdb/gdbserver/Makefile.in
@@ -217,6 +217,7 @@ SFILES = \
 	$(srcdir)/gdbsupport/gdb-dlfcn.c \
 	$(srcdir)/gdbsupport/gdb_tilde_expand.c \
 	$(srcdir)/gdbsupport/gdb_vecs.c \
+	$(srcdir)/gdbsupport/gdb_wait.c \
 	$(srcdir)/gdbsupport/netstuff.c \
 	$(srcdir)/gdbsupport/new-op.c \
 	$(srcdir)/gdbsupport/pathstuff.c \
@@ -264,6 +265,7 @@ OBS = \
 	gdbsupport/gdb-dlfcn.o \
 	gdbsupport/gdb_tilde_expand.o \
 	gdbsupport/gdb_vecs.o \
+	gdbsupport/gdb_wait.o \
 	gdbsupport/netstuff.o \
 	gdbsupport/new-op.o \
 	gdbsupport/pathstuff.o \
diff --git a/gdb/gdbserver/win32-low.c b/gdb/gdbserver/win32-low.c
index b4ee0f4..340f65b 100644
--- a/gdb/gdbserver/win32-low.c
+++ b/gdb/gdbserver/win32-low.c
@@ -34,6 +34,7 @@
 #include <process.h>
 #include "gdbsupport/gdb_tilde_expand.h"
 #include "gdbsupport/common-inferior.h"
+#include "gdbsupport/gdb_wait.h"
 
 #ifndef USE_WIN32API
 #include <sys/cygwin.h>
@@ -1511,8 +1512,24 @@ get_child_debug_event (struct target_waitstatus *ourstatus)
 		"for pid=%u tid=%x\n",
 		(unsigned) current_event.dwProcessId,
 		(unsigned) current_event.dwThreadId));
-      ourstatus->kind = TARGET_WAITKIND_EXITED;
-      ourstatus->value.integer = current_event.u.ExitProcess.dwExitCode;
+      {
+	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->kind = TARGET_WAITKIND_EXITED;
+	    ourstatus->value.integer = exit_status;
+	  }
+	else
+	  {
+	    ourstatus->kind = TARGET_WAITKIND_SIGNALLED;
+	    ourstatus->value.sig = gdb_signal_from_host (exit_signal);
+	  }
+      }
       child_continue (DBG_CONTINUE, -1);
       CloseHandle (current_process_handle);
       current_process_handle = NULL;
@@ -1607,6 +1624,7 @@ win32_wait (ptid_t ptid, struct target_waitstatus *ourstatus, int options)
 	  win32_clear_inferiors ();
 	  return ptid_t (current_event.dwProcessId);
 	case TARGET_WAITKIND_STOPPED:
+	case TARGET_WAITKIND_SIGNALLED:
 	case TARGET_WAITKIND_LOADED:
 	  OUTMSG2 (("Child Stopped with signal = %d \n",
 		    ourstatus->value.sig));