我正在使用 ctypes 调用 native c 库，传入一个专门的结构并取回另一个结构。调用 gc 时出现段错误，无法在 gdb 跟踪中找到更多详细信息:
Thread 1 "python" received signal SIGSEGV, Segmentation fault.
0x00007ffff7a5ca44 in visit_decref (op=0xf5ee10, data=0x0) at Modules/gcmodule.c:374
374 Modules/gcmodule.c: No such file or directory.
gdb) where
#0 0x00007ffff7a5ca44 in visit_decref (op=0xf5ee10, data=0x0) at Modules/gcmodule.c:374
#1 0x00007ffff798bb0c in subtype_traverse (self=0x7fff7744fd90, visit=0x7ffff7a5ca40 <visit_decref>, arg=0x0) at Objects/typeobject.c:1011
#2 0x00007ffff7a5bd77 in subtract_refs (containers=<optimized out>) at Modules/gcmodule.c:399
#3 collect (generation=generation@entry=0, n_collected=n_collected@entry=0x7fffffffb708, n_uncollectable=n_uncollectable@entry=0x7fffffffb710, nofail=nofail@entry=0) at Modules/gcmodule.c:956
#4 0x00007ffff7a5c95d in collect_with_callback (generation=0) at Modules/gcmodule.c:1128
#5 0x00007ffff7a5d1eb in collect_generations () at Modules/gcmodule.c:1151
#6 _PyObject_GC_Alloc (basicsize=<optimized out>, use_calloc=0) at Modules/gcmodule.c:1726
#7 _PyObject_GC_Malloc (basicsize=<optimized out>) at Modules/gcmodule.c:1736
代码示例是这样的:
_C_DOUBLE_P = POINTER(c_double)
_C_INT_P = POINTER(c_int)
class _IN_DATA(Structure):
_fields_ = [('in_kps', _C_DOUBLE_P),
('in_desc', _C_DOUBLE_P)
]
def __init__(self):
t = c_int
self.test = ctypes.cast(t, POINTER(c_int))
class _OUT_DATA(Structure):
_fields_ = [
('num_out_kps', ctypes.c_int),
('out_kps', _C_DOUBLE_P),
('out_desc', _C_DOUBLE_P)
]
class _IN_DATA_LIST(ctypes.Structure):
_fields_ = [
('num_crops', c_int),
('crops', POINTER(_IN_DATA))
]
def __init__(self, crops_raw_kps: List[np.ndarray], crops_raw_descriptors: List[np.ndarray]):
num_crops = len(crops_raw_kps)
self.num_crops = num_crops
crops = (POINTER(_IN_DATA) * num_crops)()
self.crops = ctypes.cast(crops, POINTER(_IN_DATA))
for i in range(num_crops):
self.crops[i].in_kps = crops_raw_kps[i].ctypes.data_as(_C_DOUBLE_P)
self.crops[i].in_desc = crops_raw_descriptors[i].ctypes.data_as(_C_DOUBLE_P)
class _OUT_DATA_LIST(ctypes.Structure):
_fields_ = [
('crops_data', ctypes.POINTER(_OUT_DATA)),
('num_results', c_int)
]
class SPPostWrapper:
def __init__(self):
self._post_processor_lib = ctypes.cdll.LoadLibrary("multitracker/custom_features/build/ffme/libffme.so")
self._post_processor_lib.py_postprocess.restype = _OUT_DATA_LIST
self._post_processor_lib.py_postprocess.argtypes = [POINTER(_IN_DATA_LIST)]
def post_process_multi(self, crops_raw_kps: List[np.ndarray], crops_raw_descriptors: List[np.ndarray]):
num_crops = len(crops_raw_kps)
adjusted_kps = [np.asarray(np.squeeze(kp), np.double) for kp in crops_raw_kps]
adjusted_desc = [np.asarray(np.squeeze(desc), np.double) for desc in crops_raw_descriptors]
crops_struct = _IN_DATA_LIST(adjusted_kps, adjusted_desc)
out_result= self._post_processor_lib.py_postprocess(ctypes.byref(crops_struct))
我在 python 中分配了 IN_DATA，在 c 代码中分配了 OUT_DATA，我尝试在 c 中使用缓存(假设 python 不会清理内存)或为每次调用分配新内存(假设 python 确实释放了 out_data 内存) - 当调用 python 的 gc 时，这两种方法都失败。
更新: 为了更好地隔离问题，我删除了 out_data 的使用，将方法设置为 void，但问题仍然存在。我还尝试将 in 数据保留为成员，我认为这可以防止数据发生，直到进程关闭。所以这一定与我分配给输入/输入列表的内存有关。
更新 2: 我能够验证只有当我在 IN_DATA_LIST 中传递超过 1 个项目(超过 1 个裁剪)时才会发生问题。这确实很奇怪......
最佳答案
在验证即使 c 代码不执行任何操作且不返回任何内容且无法解决该问题后，我最终使用了更浅的输入(和输出)，这似乎运行正常，没有段错误:
class _IN_DATA(Structure):
_fields_ = [
('num_crops', c_int),
('in_kps', _C_DOUBLE_P),
('in_desc', _C_DOUBLE_P)
]
def __init__(self, kps_flat, desc_falt, num_crops):
self.num_crops = num_crops
self.in_kps = kps_flat.ctypes.data_as(_C_DOUBLE_P)
self.in_desc = desc_falt.ctypes.data_as(_C_DOUBLE_P)
class _OUT_DATA(Structure):
_fields_ = [
('num_results', ctypes.c_int),
('results_per_crop', _C_INT_P),
('out_kps', _C_DOUBLE_P), # x,y, score
('out_desc', _C_DOUBLE_P)
]
关于python - gc 上的段错误，使用 ctypes，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/57707726/