Question

Possible Duplicate:
How do I use arrays in C++?

I have the following C code:

int main () {
    char *pathvc[MAX_PATHS];
    parsePath(pathvc);

    struct command_t command;

    command.name = lookup(command.argv, pathvc); //command.argv is: char *argv[MAX_ARGS];
}

char* lookupPath(char **argv, char **dir) {
    //Some implementation
}

This is the debug information that I am getting in the main function:

Name : pathvc Details:{0x804c208 “/usr/lib/lightdm/lightdm”,
0x804c221 “/usr/local/sbin”, 0x804c231 “/usr/local/bin”, 0x804c240
“/usr/sbin”, 0x804c24a “/usr/bin”, 0x804c253 “/sbin”, 0x804c259
“/bin”, 0x804c25e “/usr/games”, 0x0 }
Default:0xbffff0a8 Decimal:3221221544 Hex:0xbffff0a8
Binary:10111111111111111111000010101000 Octal:027777770250

Name : pathvc[0] Details:0x804c208 “/usr/lib/lightdm/lightdm”

Name : pathvc[1] Details:0x804c221 “/usr/local/sbin”

Name : pathvc[2] Details:0x804c231 “/usr/local/bin”

Name : pathvc[3] Details:0x804c240 “/usr/sbin”

Name : pathvc[4] Details:0x804c24a “/usr/bin”

Name : pathvc[5] Details:0x804c253 “/sbin”

Name : pathvc[6] Details:0x804c259 “/bin”

Name : pathvc[7] Details:0x804c25e “/usr/games”

However when I pass pathvc in the lookup function, I am getting this:

Name : dir Details:0xbffff0a8 Default:0xbffff0a8 Decimal:3221221544
Hex:0xbffff0a8 Binary:10111111111111111111000010101000
Octal:027777770250

Name : *dir Details:0x804c208 “/usr/lib/lightdm/lightdm”

Name : **dir Details:47 ‘/’

Why is it that I am passing an array of pointers to the lookup function which accepts it as a double pointer but it is only pointing to the first path instead of complete list of paths.

Pardon me if I am doing/asking a very silly question because I am not comfortable with pointers in C.

Answer 1

It’s just a matter of what the debugger knows. In the caller, the debugger can see that there are MAX_PATHS pointers. In the called function, it has no idea, so it doesn’t know how many entries to show you. If you manually asked it for the others, it would show them to you.

It’s just like this:

void someFunc(int *j)
{
   // does j point to a single integer? An array? Who knows?
}

void foo(void)
{
   int p = 3;
   int* j = &p;
   // here we know j points to one integer
   someFunc(j);
}

void foo2(void)
{
   int* j[4];
   // here we know j is an array of four pointers
   someFunc(j);
}