strlen vs sizeof

[JMS]

Let me try to simplify this.

sizeof() is an operator used to determine the size of a variable. ( will never blow up ).
strlen() is a function which counts the number of bytes in a string before the terminator '\0' character. ( will very likely blow up if your string is not null terminated. )

thus

char szString[10] = "yada";            // 4 bytes + 1 terminator, in a 10 byte array
char szZapo []     = "badabing";     // 8 bytes + 1 terminator in 9 byte array ( 8+1)

printf( "sizeof( szString ) = %d\n", sizeof( szString ));  // 10 size of array
printf( "sizeof( *szString) = %d\n", sizeof( *szString )); // 1 cause first element 'y' is a byte

printf( "strlen(szString) = %d\n", strlen(szString)); // 4  number of chars before terminator

printf( "sizeof( szZapo ) = %d\n", sizeof( szZapo ));  // 9 size allocated for array including terminator
printf( "sizeof( *szZapo) = %d\n", sizeof( *szZapo )); // 1 cause first element 'b' is a byte

printf( "strlen(szZapo) = %d\n", strlen(szZapo)); // 8  number of chars before terminator

Also don't try to use sizeof(buff) > strlen(buff) to test to see if you are corrupting memory. Cause if you've corrupted memory you are hosed before this boolean test statement is true.