swig char **作为指向char的指针* [英] swig char ** as a pointer to a char *
问题描述
我在使用swig和char **作为指向变量char *的指针时遇到麻烦(不是作为char *的列表!!!).我找不到将指针包装到char *的方法.
I'm having trouble with swig and char ** as pointer to a variable char * (not as a list of char *!!!). I couldn't find out a way to wrap the pointer to a char *.
目标是将级联的结果写入指针所引用的char *中.
The aim is to write the result of the concatenation in the char * referenced by the pointer.
以下是我的代码:
文件pointers.cpp:
File pointers.cpp:
#include "pointers.h"
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
void conc(char *str1, char *str2, char **res){
char *aux = (char *)malloc(strlen(str1)+strlen(str2)+1);
strcpy(aux,str1);
strcat(aux,str2);
strcpy(*res,aux);
free(aux);
}
文件指针.h
void conc(char *str1, char *str2, char **res)
文件指针.i
%module pointers
%{
#define SWIG_FILE_WITH_INIT
#include "pointers.h"
%}
%include "typemaps.i"
%include "cpointer.i"
%include "cstring.i"
%pointer_functions(char *, charp);
extern void conc(char *str1, char *str2, char **res);
文件setup.py:
File setup.py:
from distutils.core import setup, Extension
pointers_module = Extension('_pointers',
sources=['pointers_wrap.cxx', 'pointers.cpp'],
)
setup (name = 'pointers',
version = '0.1',
author = "SWIG Docs",
description = """Simple swig example from docs""",
ext_modules = [pointers_module],
py_modules = ["pointers"],
)
最后是python main:
Finally, the python main:
import pointers
result = new_charp()
pointers.conc("Hello ","World!", result);
print(result)
delete_charp(result)
所有这些都是使用终端命令编译的:
And all of them are compiled with terminal commands:
swig -c++ -python pointers.i
python setup.py build_ext --inplace
但是编译器返回错误:
pointers_wrap.cxx: In function ‘char** copy_charp(char*)’:
pointers_wrap.cxx:3124:58: error: invalid static_cast from type ‘char*’ to
type ‘const char*&’ return (new char *(static_cast< const char *& >(value)));
^
error: command 'gcc' failed with exit status 1
有帮助吗?
[问题更新]
按照@MarkTolonen的建议,我尝试通过以下方式更改pointers.i文件:
As suggested by @MarkTolonen I tried to change the pointers.i file in the following way:
新文件指针.i:
%module pointers
%{
#include "pointers.h"
%}
// This input typemap declares that char** requires no input parameter.
// Instead, the address of a local char* is used to call the function.
%typemap(in,numinputs=0) char** (char* tmp) %{
$1 = &tmp;
%}
// After the function is called, the char** parameter contains a malloc'ed char* pointer.
// Construct a Python Unicode object (I'm using Python 3) and append it to
// any existing return value for the wrapper.
%typemap(argout) char** %{
PyObject *obj = PyUnicode_FromString(*$1);
$result = SWIG_Python_AppendOutput($result,obj);
%}
// The malloc'ed pointer is no longer needed, so make sure it is freed.
%typemap(freearg) char** %{
free(*$1);
%}
// Now that the typemap exists, let swig wrap the header.
%include "pointers.h"
编译方式:
swig -c++ -python pointers.i
g++ --std=c++11 -fPIC -c pointers.cpp
g++ --std=c++11 -fPIC -c pointers_wrap.cxx -I/usr/local/include/python3.6m
然后我得到了错误:
In function ‘PyObject* _wrap_conc(PyObject*, PyObject*):`
pointers_wrap.cxx:3618:1: error: jump to label ‘fail’ [-fpermissive]
fail:
pointers_wrap.cxx:1222:49: note: from here
#define SWIG_fail goto fail
pointers_wrap.cxx:2999:68: note: in expansion of macro ‘SWIG_fail’
#define SWIG_exception_fail(code, msg) do { SWIG_Error(code, msg); SWIG_fail; } while(0)
pointers_wrap.cxx:3603:5: note: in expansion of macro ‘SWIG_exception_fail’
SWIG_exception_fail(SWIG_ArgError(res2), "in method '" "conc" "', argument " "2"" of type '" "char *""'");
pointers_wrap.cxx:3609:8: note: crosses initialization of ‘_object* obj’
auto obj = PyUnicode_FromString(*arg3);
pointers_wrap.cxx:3618:1: error: jump to label ‘fail’ [-fpermissive]
fail:
pointers_wrap.cxx:1222:49: note: from here
#define SWIG_fail goto fail
pointers_wrap.cxx:2999:68: note: in expansion of macro ‘SWIG_fail’
#define SWIG_exception_fail(code, msg) do { SWIG_Error(code, msg); SWIG_fail; } while(0)
pointers_wrap.cxx:3598:5: note: in expansion of macro ‘SWIG_exception_fail’
SWIG_exception_fail(SWIG_ArgError(res1), "in method '" "conc" "', argument " "1"" of type '" "char *""'");
pointers_wrap.cxx:3609:8: note: crosses initialization of ‘_object* obj’
auto obj = PyUnicode_FromString(*arg3);
pointers_wrap.cxx:3618:1: error: jump to label ‘fail’ [-fpermissive]
fail:
pointers_wrap.cxx:1222:49: note: from here
#define SWIG_fail goto fail
pointers_wrap.cxx:3595:62: note: in expansion of macro ‘SWIG_fail’
if (!PyArg_ParseTuple(args,(char *)"OO:conc",&obj0,&obj1)) SWIG_fail;
pointers_wrap.cxx:3609:8: note: crosses initialization of ‘_object* obj’
auto obj = PyUnicode_FromString(*arg3);
它在此Windows操作系统上有效,但在我的ubuntu上无效.谁能告诉我如何处理它.我真的不知道如何解决指针问题.
It works on this windows OS but not on my ubuntu. Can anyone tell how to deal with it. I really don't know how resolve my pointers problem.
推荐答案
从SWIG 3.0文档中,在§9.2.1 cpointer.i
末尾附近:
From the SWIG 3.0 documentation, near the end of §9.2.1 cpointer.i
:
注意:这些宏都不能用于安全地使用字符串(char *或char **).
Note: None of these macros can be used to safely work with strings (char * or char **).
因此,您将不得不求助于typemap.下面是一个示例:
So you will have to resort to typemaps. Below is an example:
pointers.cpp
我不得不稍微改变一下您的出处. char**
参数应该返回分配的指针,而不是释放它:
I had to change your source slightly. A char**
argument should return the allocated pointer, and not free it:
#include <string.h>
#include <stdlib.h>
#include "pointers.h"
void conc(char *str1, char *str2, char **res){
*res = (char *)malloc(strlen(str1)+strlen(str2)+1);
strcpy(*res,str1);
strcat(*res,str2);
}
pointers.h
void conc(char *str1, char *str2, char **res);
pointers.i
此版本的swig文件声明了用于处理char**
输出参数的类型映射.
This version of the swig file declares the typemaps to handle the char**
output argument.
%module pointers
%{
#include "pointers.h"
%}
// This input typemap declares that char** requires no input parameter.
// Instead, the address of a local char* is used to call the function.
%typemap(in,numinputs=0) char** (char* tmp) %{
$1 = &tmp;
%}
// After the function is called, the char** parameter contains a malloc'ed char* pointer.
// Construct a Python Unicode object (I'm using Python 3) and append it to
// any existing return value for the wrapper.
%typemap(argout) char** (PyObject* obj) %{
obj = PyUnicode_FromString(*$1);
$result = SWIG_Python_AppendOutput($result,obj);
%}
// The malloc'ed pointer is no longer needed, so make sure it is freed.
%typemap(freearg) char** %{
free(*$1);
%}
// Now that the typemap exists, let swig wrap the header.
%include "pointers.h"
test.py
import pointers
result = pointers.conc('Hello ','World!');
print(result)
输出
Hello World!
Hello World!
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