#3996: On Windows, PyOS_CheckStack is supposed to protect the interpreter from

stack overflow. But doing this, it always crashes when the stack is nearly full.

Reviewed by Martin von Loewis. Will backport to 2.6.

Misc/NEWS

@@ -12,6 +12,10 @@ What's New in Python 2.7 alpha 1
 Core and Builtins
 -----------------
 
+- Issue #3996: On Windows, the PyOS_CheckStack function would cause the
+  interpreter to abort ("Fatal Python error: Could not reset the stack!")
+  instead of throwing a MemoryError.
+
 - Issue #4367: Python would segfault during compiling when the unicodedata
   module couldn't be imported and \N escapes were present.
 

Python/pythonrun.c

@@ -1755,7 +1755,7 @@ PyOS_CheckStack(void)
 		        EXCEPTION_EXECUTE_HANDLER : 
 		        EXCEPTION_CONTINUE_SEARCH) {
 		int errcode = _resetstkoflw();
-		if (errcode)
+		if (errcode == 0)
 		{
 			Py_FatalError("Could not reset the stack!");
 		}