implements PyOS_CheckStack for Windows and MSVC. this fixes a

couple of potential stack overflows, including bug #110615.

closes patch #101238

Include/pythonrun.h

@@ -87,8 +87,20 @@ DL_IMPORT(void) PyOS_FiniInterrupts(void);
 DL_IMPORT(char *) PyOS_Readline(char *);
 extern DL_IMPORT(int) (*PyOS_InputHook)(void);
 extern DL_IMPORT(char) *(*PyOS_ReadlineFunctionPointer)(char *);
+
+/* Stack size, in "pointers" (so we get extra safety margins
+   on 64-bit platforms).  On a 32-bit platform, this translates
+   to a 8k margin. */
+#define PYOS_STACK_MARGIN 2048
+
+#if defined(WIN32) && defined(_MSC_VER)
+/* Enable stack checking under Microsoft C */
+#define USE_STACKCHECK
+#endif
+
 #ifdef USE_STACKCHECK
-int PyOS_CheckStack(void);		/* Check that we aren't overflowing our stack */
+/* Check that we aren't overflowing our stack */
+DL_IMPORT(int) PyOS_CheckStack(void);
 #endif
 
 #ifdef __cplusplus

Python/pythonrun.c

@@ -1165,3 +1165,32 @@ Py_FdIsInteractive(FILE *fp, char *filename)
 	       (strcmp(filename, "<stdin>") == 0) ||
 	       (strcmp(filename, "???") == 0);
 }
+
+
+#if defined(USE_STACKCHECK) 
+#if defined(WIN32) && defined(_MSC_VER)
+
+/* Stack checking for Microsoft C */
+
+#include <malloc.h>
+#include <excpt.h>
+
+int
+PyOS_CheckStack()
+{
+	__try {
+		/* _alloca throws a stack overflow exception if there's
+		   not enough space left on the stack */
+		_alloca(PYOS_STACK_MARGIN * sizeof(void*));
+		return 0;
+	} __except (EXCEPTION_EXECUTE_HANDLER) {
+		/* just ignore all errors */
+	}
+	return 1;
+}
+
+#endif /* WIN32 && _MSC_VER */
+
+/* Alternate implementations can be added here... */
+
+#endif /* USE_STACKCHECK */