Thread: Problems passing string to function

Hi,

I'm doing a simple dll which has a function that receives a string, makes some calculations, and returns one. Its of the type:

Code:

extern "C" __declspec(dllexport) char *read_c(char* c)
{

    static char res[2048];

        //etc

    strcat(res, c);

    return res;
}

If I give it a string like "Hi world", I get in return "H" (the first character).
I thought the function was wrong in the return, so I changed the line:

strcat(res, c);

to

strcat(res, "Hi world");

and got "Hi world". So the problem is in the passing the string c.

Can someone help me out here?

Kind regards,

JKepler

Hi,

No...don't have a clue so far...

Kind regards

JKepler

Originally Posted by laserlight

If you believe that the problem is with passing the string, then test with this code:

Code:

extern "C" __declspec(dllexport) char *read_c(char* c)
{
    static char res[2048];

    res[0] = '\0';
    strcat(res, c);

    return res;
}

Any difference? Notice that I removed the comment because this is literally the entire implementation of read_c. Nothing else, no other code that you have not shown us. Do you still have the problem?

EDIT:
Oh, you should do more: #include <assert.h> and #include <string.h> and do a pre-condition check:

Code:

extern "C" __declspec(dllexport) char *read_c(char* c)
{
    static char res[2048];

    assert(c && strlen(c) < sizeof(res));

    res[0] = '\0';
    strcat(res, c);

    return res;
}

But given that you're testing with "Hi world" this probably doesn't matter right now.

Good morning,

It worked very well laserlight Thanks.

Have a nice weekend.

Kind regards,

JKepler