python 如何从python ctypes取消引用内存位置？
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How to dereference a memory location from python ctypes?
提问by habnabit
I want to replicate the following c code in python ctypes:
我想在 python ctypes 中复制以下 c 代码：
main() {
long *ptr = (long *)0x7fff96000000;
printf("%lx",*ptr);
}
I can figure out how to call this memory location as a function pointer but not just do a normal dereference:
我可以弄清楚如何将此内存位置称为函数指针，但不仅仅是进行正常的取消引用：
from ctypes import *
"""
>>> fptr = CFUNCTYPE(None, None)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.6/ctypes/__init__.py", line 104, in CFUNCTYPE
class CFunctionType(_CFuncPtr):
TypeError: Error when calling the metaclass bases
item 1 in _argtypes_ has no from_param method
"""
fptr = CFUNCTYPE(None, c_void_p) #add c_void_p since you have to have an arg
fptr2 = fptr(0x7fff96000000)
fptr2(c_void_p(0))
#python: segfault at 7fff96000000 ip 00007fff96000000
Since there it is a segfault with the instruction pointer pointing to this memory location it is successfully calling it. However I can't get it to just read the memory location:
因为它是一个段错误，指令指针指向这个内存位置，所以它成功地调用了它。但是我不能让它只读取内存位置：
ptr = POINTER(c_long)
ptr2 = ptr(c_long(0x7fff96000000))
#>>> ptr2[0]
#140735709970432
#>>> hex(ptr2[0])
#'0x7fff96000000'
#>>> ptr2.contents
#c_long(140735709970432)
回答by habnabit
ctypes.cast.
ctypes.cast.
>>> import ctypes
>>> c_long_p = ctypes.POINTER(ctypes.c_long)
>>> some_long = ctypes.c_long(42)
>>> ctypes.addressof(some_long)
4300833936
>>> ctypes.cast(4300833936, c_long_p)
<__main__.LP_c_long object at 0x1005983b0>
>>> ctypes.cast(4300833936, c_long_p).contents
c_long(42)
