[英]Can't pass a string to char * arg of function call in dll in python
I am trying to use a dll in Python source using the ctypes. 我正在尝试使用ctypes在Python源代码中使用dll。 I began reading it from Python documentation as I am new to this. 我开始从Python文档中读取它,因为我是新手。 After successfully loading the dll in Python, when I try to pass a string to a function which expects a char *
, it gives me 在Python中成功加载dll之后,当我尝试将字符串传递给期望char *
的函数时,它给了我
"ValueError: Procedure probably called with too many arguments (4 bytes in excess)". “ValueError:过程可能用太多的参数调用(超过4个字节)”。
I also tried looking at other posts but couldn't resolve the problem. 我也试过看其他帖子但无法解决问题。
I tried different approaches to pas this string such as using byref()
and pointer()
but it didn't change the outcome. 我尝试了不同的方法来使用这个字符串,例如使用byref()
和pointer()
但它没有改变结果。 I also tried with WINFUNCTYPE
but failed. 我也试过WINFUNCTYPE
但是失败了。 The dll that I'm using is windll. 我正在使用的dll是windll。
Here's a test program I wrote in python: 这是我在python中编写的测试程序:
from ctypes import *
lpDLL=WinDLL("C:\some_path\myDll.dll")
print lpDLL
IP_ADDR = create_string_buffer('192.168.100.228')
#IP_ADDR = "192.168.100.228"
#IP_ADDR = c_char_p("192.168.100.228")
print IP_ADDR, IP_ADDR.value
D_Init=lpDLL.D_Init
D_InitTester=lpDLL.D_InitTester
#D_InitTesterPrototype = WINFUNCTYPE(c_int, c_char_p)
#D_InitTesterParamFlags = ((1, "ipAddress", None),)
#D_InitTester = d_InitTesterPrototype(("D_InitTester", lpDLL), D_InitTesterParamFlags)
try:
D_Init()
D_InitTester("192.168.100.254")
except ValueError, msg:
print "Init_Tester Failed"
print msg
Here's how the D_InitTester is implemented in a cpp file which is available in dll exports, 以下是在dll导出中可用的cpp文件中实现D_InitTester的方法,
D_API int D_InitTester(char *ipAddress)
{
int err = ERR_OK;
if (LibsInitialized)
{
...
some code;
...
else
{
err = hndl->ConInit(ipAddress);
}
if ( 0 < err )
{
err = ERR_NO_CONNECTION;
}
else
{
nTesters = 1;
InstantiateAnalysisClasses();
InitializeTesterSettings();
if(NULL != hndl->hndlFm)
{
FmInitialized = true;
}
}
}
else
{
err = ERR_NOT_INITIALIZED;
}
return err;
}
Your help is greatly appreciated. 非常感谢您的帮助。
Most likely the cause of the error is a mismatch of calling conventions. 很可能导致错误的原因是调用约定不匹配。 I'm guessing your C++ DLL exports functions with cdecl
convention but your use of WinDLL
implies stdcall
. 我猜你的C ++ DLL导出函数与cdecl
约定,但你使用WinDLL
意味着stdcall
。
Create your library like this to use cdecl
: 像这样创建你的库来使用cdecl
:
lpDLL=CDLL("C:\some_path\myDll.dll")
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