为什么这样做：
In [17]: %%cython -f
...: from libc.string cimport memcpy
...:
...: DEF KLEN = 5
...: DEF TRP_KLEN = KLEN * 3
...:
...: cdef:
...: unsigned char k[KLEN]
...: unsigned char kk[TRP_KLEN]
...: kk = bytearray(b'12345abcde!@#$%')
...: memcpy(&k, &kk[5], KLEN)
...: print(k)
b'abcde'
与此同时：
In [16]: %%cython -f
...: from libc.string cimport memcpy
...:
...: DEF KLEN = 5
...: DEF TRP_KLEN = KLEN * 3
...: ctypedef unsigned char SingleKey[KLEN]
...: ctypedef unsigned char TripleKey[TRP_KLEN]
...:
...: cdef:
...: SingleKey k
...: TripleKey kk
...: kk = bytearray(b'12345abcde!@#$%')
...: memcpy(&k, &kk[5], KLEN)
...: print(k)
抛出一个晦涩的错误，它没有直接提及我的代码：
---------------------------------------------------------------------------
AssertionError Traceback (most recent call last)
<ipython-input-16-a4bb608248b0> in <module>()
----> 1 get_ipython().run_cell_magic('cython', '-f', "from libc.string cimport memcpy\n\nDEF KLEN = 5\nDEF TRP_KLEN = KLEN * 3\nctypedef unsigned char SingleKey[KLEN]\nctypedef unsigned char DoubleKey[TRP_KLEN]\n\ncdef:\n SingleKey k[KLEN]\n DoubleKey kk[TRP_KLEN]\nkk = bytearray(b'12345abcde!@#$%')\nmemcpy(&k, &kk[5], KLEN)\nprint(k)")
/usr/lib/python3.6/site-packages/IPython/core/interactiveshell.py in run_cell_magic(self, magic_name, line, cell)
2165 magic_arg_s = self.var_expand(line, stack_depth)
2166 with self.builtin_trap:
-> 2167 result = fn(magic_arg_s, cell)
2168 return result
2169
<decorator-gen-118> in cython(self, line, cell)
/usr/lib/python3.6/site-packages/IPython/core/magic.py in <lambda>(f, *a, **k)
185 # but it's overkill for just that one bit of state.
186 def magic_deco(arg):
--> 187 call = lambda f, *a, **k: f(*a, **k)
188
189 if callable(arg):
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Build/IpythonMagic.py in cython(self, line, cell)
318 extension = None
319 if need_cythonize:
--> 320 extensions = self._cythonize(module_name, code, lib_dir, args, quiet=args.quiet)
321 assert len(extensions) == 1
322 extension = extensions[0]
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Build/IpythonMagic.py in _cythonize(self, module_name, code, lib_dir, args, quiet)
426 elif sys.version_info[0] >= 3:
427 opts['language_level'] = 3
--> 428 return cythonize([extension], **opts)
429 except CompileError:
430 return None
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Build/Dependencies.py in cythonize(module_list, exclude, nthreads, aliases, quiet, force, language, exclude_failures, **options)
1024 if not nthreads:
1025 for args in to_compile:
-> 1026 cythonize_one(*args)
1027
1028 if exclude_failures:
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Build/Dependencies.py in cythonize_one(pyx_file, c_file, fingerprint, quiet, options, raise_on_failure, embedded_metadata, full_module_name, progress)
1127 any_failures = 0
1128 try:
-> 1129 result = compile_single(pyx_file, options, full_module_name=full_module_name)
1130 if result.num_errors > 0:
1131 any_failures = 1
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Main.py in compile_single(source, options, full_module_name)
647 recursion.
648 """
--> 649 return run_pipeline(source, options, full_module_name)
650
651
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Main.py in run_pipeline(source, options, full_module_name, context)
497
498 context.setup_errors(options, result)
--> 499 err, enddata = Pipeline.run_pipeline(pipeline, source)
500 context.teardown_errors(err, options, result)
501 return result
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Pipeline.py in run_pipeline(pipeline, source, printtree)
352 exec("def %s(phase, data): return phase(data)" % phase_name, exec_ns)
353 run = _pipeline_entry_points[phase_name] = exec_ns[phase_name]
--> 354 data = run(phase, data)
355 if DebugFlags.debug_verbose_pipeline:
356 print(" %.3f seconds" % (time() - t))
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Pipeline.py in run(phase, data)
332
333 def run(phase, data):
--> 334 return phase(data)
335
336 error = None
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Pipeline.py in generate_pyx_code_stage(module_node)
50 def generate_pyx_code_stage_factory(options, result):
51 def generate_pyx_code_stage(module_node):
---> 52 module_node.process_implementation(options, result)
53 result.compilation_source = module_node.compilation_source
54 return result
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/ModuleNode.py in process_implementation(self, options, result)
140 self.find_referenced_modules(env, self.referenced_modules, {})
141 self.sort_cdef_classes(env)
--> 142 self.generate_c_code(env, options, result)
143 self.generate_h_code(env, options, result)
144 self.generate_api_code(env, options, result)
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/ModuleNode.py in generate_c_code(self, env, options, result)
376 # generate normal variable and function definitions
377 self.generate_variable_definitions(env, code)
--> 378 self.body.generate_function_definitions(env, code)
379 code.mark_pos(None)
380 self.generate_typeobj_definitions(env, code)
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Nodes.py in generate_function_definitions(self, env, code)
436 #print "StatListNode.generate_function_definitions" ###
437 for stat in self.stats:
--> 438 stat.generate_function_definitions(env, code)
439
440 def generate_execution_code(self, code):
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Nodes.py in generate_function_definitions(self, env, code)
9242 entry.cname = cname
9243
-> 9244 self.node.generate_function_definitions(env, code)
9245
9246 def generate_execution_code(self, code):
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Nodes.py in generate_function_definitions(self, env, code)
1974 # ----- Function body -----
1975 # -------------------------
-> 1976 self.generate_function_body(env, code)
1977
1978 code.mark_pos(self.pos, trace=False)
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Nodes.py in generate_function_body(self, env, code)
1736
1737 def generate_function_body(self, env, code):
-> 1738 self.body.generate_execution_code(code)
1739
1740 def generate_function_definitions(self, env, code):
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Nodes.py in generate_execution_code(self, code)
442 for stat in self.stats:
443 code.mark_pos(stat.pos)
--> 444 stat.generate_execution_code(code)
445
446 def annotate(self, code):
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Nodes.py in generate_execution_code(self, code)
6185 for i, if_clause in enumerate(self.if_clauses):
6186 self._set_branch_hint(if_clause, if_clause.body)
-> 6187 if_clause.generate_execution_code(code, end_label, is_last=i == last)
6188 if self.else_clause:
6189 code.mark_pos(self.else_clause.pos)
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Nodes.py in generate_execution_code(self, code, end_label, is_last)
6247 self.condition.generate_disposal_code(code)
6248 self.condition.free_temps(code)
-> 6249 self.body.generate_execution_code(code)
6250 code.mark_pos(self.pos, trace=False)
6251 if not (is_last or self.body.is_terminator):
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Nodes.py in generate_execution_code(self, code)
442 for stat in self.stats:
443 code.mark_pos(stat.pos)
--> 444 stat.generate_execution_code(code)
445
446 def annotate(self, code):
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/UtilNodes.py in generate_execution_code(self, code)
324 def generate_execution_code(self, code):
325 self.setup_temp_expr(code)
--> 326 self.body.generate_execution_code(code)
327 self.teardown_temp_expr(code)
328
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Nodes.py in generate_execution_code(self, code)
6605 self.item.generate_evaluation_code(code)
6606 self.target.generate_assignment_code(self.item, code)
-> 6607 self.body.generate_execution_code(code)
6608 code.mark_pos(self.pos)
6609 code.put_label(code.continue_label)
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Nodes.py in generate_execution_code(self, code)
442 for stat in self.stats:
443 code.mark_pos(stat.pos)
--> 444 stat.generate_execution_code(code)
445
446 def annotate(self, code):
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Nodes.py in generate_execution_code(self, code)
5100 def generate_execution_code(self, code):
5101 code.mark_pos(self.pos)
-> 5102 self.generate_rhs_evaluation_code(code)
5103 self.generate_assignment_code(code)
5104
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/Nodes.py in generate_rhs_evaluation_code(self, code)
5387
5388 def generate_rhs_evaluation_code(self, code):
-> 5389 self.rhs.generate_evaluation_code(code)
5390
5391 def generate_assignment_code(self, code, overloaded_assignment=False):
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/ExprNodes.py in generate_evaluation_code(self, code)
718 self.allocate_temp_result(code)
719
--> 720 self.generate_result_code(code)
721 if self.is_temp and not (self.type.is_string or self.type.is_pyunicode_ptr):
722 # If we are temp we do not need to wait until this node is disposed
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/ExprNodes.py in generate_result_code(self, code)
13135
13136 code.putln(self.type.from_py_call_code(
> 13137 self.arg.py_result(), self.result(), self.pos, code, from_py_function=from_py_function))
13138 if self.type.is_pyobject:
13139 code.put_gotref(self.py_result())
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/PyrexTypes.py in from_py_call_code(self, source_code, result_code, error_pos, code, from_py_function, error_condition)
512 source_code, result_code, error_pos, code,
513 from_py_function or self.from_py_function,
--> 514 error_condition or self.error_condition(result_code)
515 )
516
~/code/lsup/virtualenv/lib/python3.6/site-packages/Cython/Compiler/PyrexTypes.py in from_py_call_code(self, source_code, result_code, error_pos, code, from_py_function, error_condition)
2481 def from_py_call_code(self, source_code, result_code, error_pos, code,
2482 from_py_function=None, error_condition=None):
-> 2483 assert not error_condition, '%s: %s' % (error_pos, error_condition)
2484 call_code = "%s(%s, %s, %s)" % (
2485 from_py_function or self.from_py_function,
AssertionError: (<StringSourceDescriptor:carray.from_py>, 87, 19): (!__pyx_t_11) && PyErr_Occurred()
这在我的1000多行程序中尤其成问题，在那里我不得不找出导致问题的原因。删除已分配的char数组的所有ctypedefs均会删除该错误，但我想知道是什么引起的。
谢谢。
更新
注意：这不是一个以NUL终止的字符串，而是一个字节序列，该字节序列可能在任何地方都有NUL。这就是为什么我使用memcpy而不是字符串函数或常规=分配的原因。