将struct传递给dll

Question

I want to pass several data to a Dll function, so I am thinking of creating a struct and passing them to Dll dunction via a struct such as follow:

struct options
{
int op1,
int op2,
int op3,
char * op4,
...
char * op10
}

 void dllFunction(options myOptions)

As the dll should be implemented in a way that works on windows platform irrespective of what is the development tools is it, I am wondering :

Is it valid to send data in this way? note that the structure members all are basic c types (int, float, double, ...).

Why I am worried about it? as you know, different compilers implemented std classes differently, so you can not pass std classes over dll boundaries, but I am not sure if all of the compilers are placing struct members in the same way or they are not, as if they are not, then the code may not work with some compilers.

is a struct is a simple c type data type?

If I can not use a struct for this purpose, what is the best way to do this (passing a lot of data to a function inside a dll function?

Answer 1

The C ABI is well-defined and stable, so this works fine. To ensure that you are getting that C ABI if you are compiling as C++, you will need to annotate with extern "C" .

The only thing you'll have trouble with is pointers to memory. Since there is no guarantee that the application and the DLL are using compatible run-time libraries, the code that allocated the memory must always be the one that frees it. You cannot have, for example, the application malloc a buffer, pass a pointer to that buffer to the DLL, and then expect the DLL to free the buffer. Either the application needs to free the buffer (since it's the one that called malloc ), or the application will need to export a MyFree function that the DLL will call to free the memory.