Fixed bug related to non-usage of local buffer variable

Cython/Compiler/Buffer.py

@@ -63,8 +63,8 @@ class IntroduceBufferAuxiliaryVars(CythonTransform):
             cname = scope.mangle(Naming.bufstruct_prefix, name)
             bufinfo = scope.declare_var(name="$%s" % cname, cname=cname,
                                         type=PyrexTypes.c_py_buffer_type, pos=node.pos)
-
-            bufinfo.used = True
+            if entry.is_arg:
+                bufinfo.used = True # otherwise, NameNode will mark whether it is used
 
             def var(prefix, idx, initval):
                 cname = scope.mangle(prefix, "%d_%s" % (idx, name))

Cython/Compiler/Nodes.py

@@ -935,6 +935,7 @@ class FuncDefNode(StatNode, BlockNode):
         # goto statement in error cleanup above
         code.put_label(code.return_label)
         for entry in lenv.buffer_entries:
+            if entry.used:
                 code.putln("%s;" % Buffer.get_release_buffer_code(entry))
         # ----- Return cleanup for both error and no-error return
         code.put_label(code.return_from_error_cleanup_label)

tests/run/bufaccess.pyx

@@ -34,6 +34,15 @@ def testcas(a):
 # Buffer acquire and release tests
 #
 
+@testcase
+def nousage():
+    """
+    >>> True
+    True
+    """
+    cdef object[int, 2] buf
+    # this used not to compile
+
 @testcase
 def acquire_release(o1, o2):
     """