fix ticket 154: C compilation error for unused local buffer variables

CHANGES.rst

@@ -12,6 +12,9 @@ Bugs fixed
 
 * Invalid C code for some builtin methods.  This fixes ticket 856.
 
+* Invalid C code for unused local buffer variables.
+  This fixes ticket 154.
+
 * Test failures on 32bit systems.  This fixes ticket 857.
 
 * Code that uses "from xyz import *" and global C struct/union/array

Cython/Compiler/Nodes.py

@@ -1955,6 +1955,7 @@ class FuncDefNode(StatNode, BlockNode):
                 code.putln("{ PyObject *__pyx_type, *__pyx_value, *__pyx_tb;")
                 code.putln("__Pyx_ErrFetch(&__pyx_type, &__pyx_value, &__pyx_tb);")
                 for entry in lenv.buffer_entries:
+                    if entry.used:
                         Buffer.put_release_buffer_code(code, entry)
                     #code.putln("%s = 0;" % entry.cname)
                 code.putln("__Pyx_ErrRestore(__pyx_type, __pyx_value, __pyx_tb);}")

tests/buffers/bufaccess.pyx

@@ -45,6 +45,7 @@ def nousage():
     cdef object[int, ndim=2] buf
 
 
+@testcase
 def disabled_usage(obj):
     """
     The challenge here is just compilation.
@@ -57,6 +58,19 @@ def disabled_usage(obj):
     return obj
 
 
+@testcase
+def nousage_cleanup(x):
+    """
+    >>> nousage_cleanup(False)
+    >>> nousage_cleanup(True)
+    Traceback (most recent call last):
+    RuntimeError
+    """
+    cdef object[int, ndim=2] buf
+    if x:
+        raise RuntimeError()
+
+
 @testcase
 def acquire_release(o1, o2):
     """