求助帖 关于python ctypes调用

kyq_linux

/ # ./_install/bin/python
Python 2.7.3 (default, Apr  7 2020, 12:06:28)
[GCC 4.9.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from ctypes import *
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/_install/lib/python2.7/ctypes/__init__.py", line 10, in <module>
    from _ctypes import Union, Structure, Array
ImportError: No module named _ctypes
好像是没有编译这个ctypes 模块 但是找了下资料都说这个模块是python 自带的不需要安装？  
请问下这是怎么回事？

w282529350

python 3.7.0测试没有问题
可能从python3开始自带了吧

dreambox

python 3.7没问题，python2的问题不要去纠结了，没啥意义，赶紧换py3

styleno1

有的，搜了下官方Wiki：https://docs.python.org/2.7/library/ctypes.html

kyq_linux

w282529350 发表于 2020-4-7 14:45
python 3.7.0测试没有问题
可能从python3开始自带了吧

可是我编译python 3.7 也是出现这个问题 编译不报错 但是ctypes 没有添加进入

kyq_linux

dreambox 发表于 2020-4-7 21:15
python 3.7没问题，python2的问题不要去纠结了，没啥意义，赶紧换py3

换了依然还是这个问题。。。

kyq_linux

Python build finished successfully!
The necessary bits to build these optional modules were not found:
_bz2                  _curses               _curses_panel      
_dbm                  _gdbm                 _hashlib           
_lzma                 _sqlite3              _ssl               
_tkinter              _uuid                 readline           
zlib                                                           
To find the necessary bits, look in setup.py in detect_modules() for the module's name.


The following modules found by detect_modules() in setup.py, have been
built by the Makefile instead, as configured by the Setup files:
_abc                  atexit                pwd               
time                                                           


Failed to build these modules:
_ctypes                                                        


Could not build the ssl module!
Python requires an OpenSSL 1.0.2 or 1.1 compatible libssl with X509_VERIFY_PARAM_set1_host().
LibreSSL 2.6.4 and earlier do not provide the necessary APIs, https://github.com/libressl-portable/portable/issues/381

running build_scripts
creating build/scripts-3.7
copying and adjusting /home/kyq/python/Python-3.7.5/Tools/scripts/pydoc3 -> build/scripts-3.7
copying and adjusting /home/kyq/python/Python-3.7.5/Tools/scripts/idle3 -> build/scripts-3.7
copying and adjusting /home/kyq/python/Python-3.7.5/Tools/scripts/2to3 -> build/scripts-3.7
copying and adjusting /home/kyq/python/Python-3.7.5/Tools/scripts/pyvenv -> build/scripts-3.7
changing mode of build/scripts-3.7/pydoc3 from 664 to 775
changing mode of build/scripts-3.7/idle3 from 664 to 775
changing mode of build/scripts-3.7/2to3 from 664 to 775
changing mode of build/scripts-3.7/pyvenv from 664 to 775
renaming build/scripts-3.7/pydoc3 to build/scripts-3.7/pydoc3.7
renaming build/scripts-3.7/idle3 to build/scripts-3.7/idle3.7
renaming build/scripts-3.7/2to3 to build/scripts-3.7/2to3-3.7
renaming build/scripts-3.7/pyvenv to build/scripts-3.7/pyvenv-3.7
/usr/bin/install -c -m 644 ./Tools/gdb/libpython.py python-gdb.py
arm-linux-gnueabihf-gcc -c -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall    -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -Werror=implicit-function-declaration   -I. -I./Include    -DPy_BUILD_CORE -o Programs/_testembed.o ./Programs/_testembed.c
arm-linux-gnueabihf-gcc     -Xlinker -export-dynamic -o Programs/_testembed Programs/_testembed.o libpython3.7m.a -lcrypt -lpthread -ldl  -lpthread -lutil   -lm  
sed -e "s,@EXENAME@,/home/kyq/python/Python-3.7.5/pyinstall/bin/python3.7m," < ./Misc/python-config.in >python-config.py
LC_ALL=C sed -e 's,\$(\([A-Za-z0-9_]*\)),\$\{\1\},g' < Misc/python-config.sh >python-config

kyq_linux

我编译了3.7.5  2.7.3 都出现了这样的问题 编译通过 但是ctypes 模块没有添加进入。。。 看了很多帖子 都是说要安装什么libffi-dev   安装过后 没有 任何反应。。不知道还要做些什么。。。

liansh2002

貌似libffi-dev装完后，要ldconfig重新加载，然后再重编译安装python
参考这个: https://stackoverflow.com/questi ... lue-from-module-mul

diandianer

python 3.7.0没有问题

styleno1

刚试了下，执行正常：

1. from ctypes import *
   
2. 
   
3. value = c_bool(1)
   
4. print(value)

复制代码

kyq_linux

root@ATK-IMX6U:~# python2.7
Python 2.7.11 (default, Aug 14 2019, 18:06:34)
[GCC 5.3.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from ctypes import *
>>> mylib = CDLL('/home/root/test/libbeep.so')
>>> mylib.beep_on()
Segmentation fault

kyq_linux

$CC ./test/beepApp.c  -fPIC -shared -o ./test/libbeep.so


beepApp.c
内容如下


int beep_on(void);
int beep_off(void);
int beep_on()
{
...
}
int beep_off()
{
...
}

kyq_linux

>>> mylib.beep_on()
Segmentation fault

调用so库中的beep_on 出现 Segmentation fault
是我用的有问题吗。。。。

kyq_linux

liansh2002 发表于 2020-4-8 10:53
貌似libffi-dev装完后，要ldconfig重新加载，然后再重编译安装python
参考这个: https://stackoverflow.com ...

好的蟹蟹 ! 已经能正常用了