I thought about doing that, the problem is that I don't know how would that affect memory handling. I mean, If I'd had a function like this in C++:

string bleh(void);

[download]

I could easily have a C wrapper that would do:

const char* blehC(void) {
  return bleh(void).c_str();
}

[download]

But... this has a big problem: you are returning a pointer to a local variable (the returned string inside blehC is local to blehC).

So, what I would need is to tell XS/perl/whatever to give me a piece of memory that it considers a scalar where I can write to (wether it is a scalar being returned or a reference to a scalar which I receive). I guess that I don't have an alternative to write something in the CODE: section, but I really wouldn't know how to do that nor how the C/C++ function should look like. I mean, in C I don't have references, so I would be taking a char*, but... how do I know how much space do I have to write? When I write to a std::string I'm indirectly allocating memory and returning to something a user gave me. So, at C level, how does XS/perl/whatever knows how to free the memory I return? assuming that I do something like this:

char* respondC(const char* input, const char* username) {
  char* ret = NULL;
  if (respond(input, username, cpp_ret)) {
    string cpp_ret;
    ret = new char[cpp_ret.length()+1];
    strncpy(ret, cpp_ret.c_str(), cpp_ret.length());
  }
  return ret;
}

[download]
(ignoring possible fencepost errors)

So, that is what is haunting me... Maybe there's a way to not even write at CODE: but just write a C function that takes a scalar reference (SV* or something like that) where I can copy (as a string) the result of the C++ function. Anyway, that would be ideal, not sure if possible.

In reply to Re^2: C++ strings, references and XS (char*) by v01d
in thread C++ strings, references and XS by v01d

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