Re: Cast void pointer to C struct pointer and access its members?

Good catch Jake!

It works.  So #1 and #2 are solved.

Is there a more elegant way to cast void* into C struct?  So that I don't
have to update the SWIG interface file for each new struct my header has.

Thanks in advance!

On Tue, Sep 28, 2021 at 8:37 PM Jake <[email protected]> wrote:

> You've passed `Foo*` as `T` when your return type is `T*`, try:
>
> %template(convert_foo) convert<Foo>;
>
> -Jake
>
> On Mon, Sep 27, 2021 at 11:31 PM H C <[email protected]> wrote:
>
>> Hi,
>>
>> I have TestCast.i:
>>
>> %module test_cast
>>
>> %{
>> #include "TestCast.hpp"
>> %}
>>
>> %include <stdint.i>
>>
>> %include "TestCast.hpp"
>> %template(convert_foo) convert<Foo*>;
>> %template(convert_bar) convert<Bar*>;
>>
>>
>>
>> and TestCast.hpp:
>>
>> #include <cstdint>
>> #include <iostream>
>>
>> #pragma pack(1)
>> struct Foo {
>> uint8_t a;
>> char b;
>> int32_t c;
>> };
>> #pragma pack()
>>
>> void* get_foo() {
>> static Foo foo{1, 'b', 65535};
>> return static_cast<void*>(&foo);
>> }
>>
>> template <typename T>
>> T* convert(void* data) noexcept {
>> return static_cast<T*>(data);
>> }
>>
>> I managed to cast the void pointer returned by get_foo() to Foo**:
>> >>> import test_cast
>> >>> foo_void_ptr = test_cast.get_foo()
>> >>> print(foo_void_ptr)
>> <Swig Object of type 'void *' at 0x7f9613abd990>
>> >>> foo_ptr = test_cast.convert_foo(foo_void_ptr)
>> >>> print(foo_ptr)
>> <Swig Object of type 'Foo **' at 0x7f9613af3f00>
>>
>> Questions:
>> 1.  How can I get Foo* instead of Foo**?
>> 2.  How can I access the member in Foo in python?
>> 3.  Is there a more elegant way to cast void* into C struct?
>>
>> Thanks!
>> _______________________________________________
>> Swig-user mailing list
>> [email protected]
>> https://lists.sourceforge.net/lists/listinfo/swig-user
>>
>

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