Prefix an internal C macro with "__Pyx_" to avoid accidental namespace collisions with user code.

Cython/Compiler/ExprNodes.py

@@ -11576,7 +11576,7 @@ class DivNode(NumBinopNode):
                         minus1_check = '(!(((%s)-1) > 0)) && unlikely(%s == (%s)-1)' % (
                             type_of_op2, self.operand2.result(), type_of_op2)
                     code.putln("else if (sizeof(%s) == sizeof(long) && %s "
-                               " && unlikely(UNARY_NEG_WOULD_OVERFLOW(%s))) {" % (
+                               " && unlikely(__Pyx_UNARY_NEG_WOULD_OVERFLOW(%s))) {" % (
                                self.type.empty_declaration_code(),
                                minus1_check,
                                self.operand1.result()))

Cython/Utility/Overflow.c

@@ -305,7 +305,6 @@ static CYTHON_INLINE {{TYPE}} __Pyx_lshift_{{NAME}}_checking_overflow({{TYPE}} a
 
 /////////////// UnaryNegOverflows.proto ///////////////
 
-//FIXME: shouldn't the macro name be prefixed by "__Pyx_" ?  Too late now, I guess...
 // from intobject.c
-#define UNARY_NEG_WOULD_OVERFLOW(x)    \
+#define __Pyx_UNARY_NEG_WOULD_OVERFLOW(x)    \
         (((x) < 0) & ((unsigned long)(x) == 0-(unsigned long)(x)))