Comparing Strings and pointers

Question

I'm still trying to wrap my head around pointers and strings in C for a class I'm taking. In the below example, g_reservations[][] is a global variable (not ideal, I know, but I cant change that).

error: Warning C4047 'function': 'const char *' differs in levels of indirection from 'char' EconoAirBeta ... 299

*passenger is a pointer, so do create a pointer to the global? That seems unnecessary...

how do i make this work? I feel I'm missing some incredibly easy concept my brain cant seem to grasp....

unsigned int FindSeatWithPassenger(const char *passengerName)
{
    unsigned int seat = 0;
    for (seat = 0; seat < NUM_SEATS; ++seat)
    {
        if ( strncmp(passengerName, g_reservations[seat][0], NAME_LENGTH) != 0) //error here with global variable
        {
            return seat;
            break;
        }
    }
    return '\0';
}

Global declaration:

#define NAME_LENGTH 10
#define NAME_BUFFER_LENGTH ( NAME_LENGTH + 1 )
char g_reservations[NUM_SEATS][NAME_BUFFER_LENGTH];

Coyld you please show how g_reservations[seat][0] matrix is declared ? Is it char** ? — Victor Gubin
– Victor Gubin, Commented Nov 9, 2019 at 16:30
Use g_reservations[seat] in strncmp. The second index denotes the characters of the string you want to compare. — Paul Ogilvie
– Paul Ogilvie, Commented Nov 9, 2019 at 16:39
Note: at the end you are formally returning a char, whereas the function should return an usigned int. At the end, use return 0; — Paul Ogilvie
– Paul Ogilvie, Commented Nov 9, 2019 at 16:43

chux · Accepted Answer · 2019-11-09 16:53:59Z

3

Wrong type

Just as the error says.

g_reservations[seat][0] is a char.

int strncmp(const char *s1, const char *s2, size_t n) expects a char * for s2.

Use &g_reservations[seat][0] or simply g_reservations[seat]

strncmp(passengerName, g_reservations[seat], NAME_LENGTH)

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