How do I pass an array as a parameter?

This is driving me crazy:

I have function

void gst_init(int *argc, char **argv[]);

in the gstreamer api and I want to call it with some parameters I define, like:

int argc = 2;
char* argv[2] = {"myvalue1", "myvalue2"};
gst_init(&argc, &argv);

This code doesn't compile (I get error C2664):

error C2664: 'gst_init' : cannot convert parameter 2 from 'char *(*)[2]' to 'char **[]'

The question: How do I define the argv value to pass it as a parameter? I've been using C++ for over 5 years, but I haven't used a raw array since ... high-school I 开发者_开发技巧think (more than five years ago).

Edit: I'm using VS2010 Express.

Normally you would follow the instructions in the manual, and pass pointers to the arguments provided by main, so that gstreamer can remove the arguments which it handles.

#include <stdio.h>
#include <gst/gst.h>

int main ( int argc, char *argv[] )
{
    gst_init (&argc, &argv);
    // handle the remaining argc values of argv

If you want to create your own arguments, then create the same sort of array which main would have:

void gst_init(int *argc, char **argv[])
{
    // strip one argument
    --*argc;
    ++*argv;
}

void foo ()
{
    int argc = 2;

    char* args[] = {"myvalue1", "myvalue2"};
    char** argv = args;

    for(int i= 0; i < argc; ++i)
        printf("%s\n", argv[i]);

    gst_init(&argc, &argv);

    for(int i= 0; i < argc; ++i)
        printf("%s\n", argv[i]);
}

If you're not using C99, it's easier to have a separate pointer to the local array of string literals. Using C99, you could just write char** argv = (char*[]){"myvalue1", "myvalue2"}; to start with a pointer to the first element in an anonymous array.

You need to pass a pointer to a variable pointing to the array rather than a pointer to the first element in the array; in the first case the degradation of an array parameter to a pointer achieves the same effect as the second case declaring a pointer local variable - you then can pass the address of this variable and the function can modify it. sizeof( args) is 8 on a 32bit machine as the compiler deduces the number of elements in the array; sizeof(argv) is 4, therefore ++args would move the pointer to the end of the array rather than to the next element as ++argv does. The compiler protects you from such an operation.

But normally you'd use it in the way the manual suggests.

Try

int argc = 2;
char* arg1[1] = {"myvalue1"};
char* arg2[1] = {"myvalue2"};
char** argv[2] = { arg1, arg2 };
gst_init(&argc, argv);

char **argv[] is an array of char**, which is analogous to an array of char* arrays.

OTOH what you tried to pass as parameter is shown as char *(*)[2]: a pointer to an array of char*.