bpo-31701: faulthandler: ignore MSC and COM Windows exception (#3929)

bpo-31701: On Windows, faulthandler.enable() now ignores MSC and COM
exceptions.

Lib/test/test_faulthandler.py

@@ -748,6 +748,22 @@ class FaultHandlerTests(unittest.TestCase):
                 3,
                 name)
 
+    @unittest.skipUnless(MS_WINDOWS, 'specific to Windows')
+    def test_ignore_exception(self):
+        for exc_code in (
+            0xE06D7363,   # MSC exception ("Emsc")
+            0xE0434352,   # COM Callable Runtime exception ("ECCR")
+        ):
+            code = f"""
+                    import faulthandler
+                    faulthandler.enable()
+                    faulthandler._raise_exception({exc_code})
+                    """
+            code = dedent(code)
+            output, exitcode = self.get_output(code)
+            self.assertEqual(output, [])
+            self.assertEqual(exitcode, exc_code)
+
     @unittest.skipUnless(MS_WINDOWS, 'specific to Windows')
     def test_raise_nonfatal_exception(self):
         # These exceptions are not strictly errors. Letting

Misc/NEWS.d/next/Library/2017-10-09-17-42-30.bpo-31701.NRrVel.rst

+On Windows, faulthandler.enable() now ignores MSC and COM exceptions.

Modules/faulthandler.c

@@ -360,6 +360,23 @@ faulthandler_fatal_error(int signum)
 }
 
 #ifdef MS_WINDOWS
+static int
+faulthandler_ignore_exception(DWORD code)
+{
+    /* bpo-30557: ignore exceptions which are not errors */
+    if (!(code & 0x80000000)) {
+        return 1;
+    }
+    /* bpo-31701: ignore MSC and COM exceptions
+       E0000000 + code */
+    if (code == 0xE06D7363 /* MSC exception ("Emsc") */
+        || code == 0xE0434352 /* COM Callable Runtime exception ("ECCR") */) {
+        return 1;
+    }
+    /* Interesting exception: log it with the Python traceback */
+    return 0;
+}
+
 static LONG WINAPI
 faulthandler_exc_handler(struct _EXCEPTION_POINTERS *exc_info)
 {
@@ -367,9 +384,8 @@ faulthandler_exc_handler(struct _EXCEPTION_POINTERS *exc_info)
     DWORD code = exc_info->ExceptionRecord->ExceptionCode;
     DWORD flags = exc_info->ExceptionRecord->ExceptionFlags;
 
-    /* bpo-30557: only log fatal exceptions */
-    if (!(code & 0x80000000)) {
-        /* call the next exception handler */
+    if (faulthandler_ignore_exception(code)) {
+        /* ignore the exception: call the next exception handler */
         return EXCEPTION_CONTINUE_SEARCH;
     }