declaring and passing char array of different sizes correctly

Question

I like to define a method that receives a char array of variable size.

This is my current definition:

+(int) findStartIndex: (NSData*)buffer  searchPattern: (char*) searchPattern;

And this is where I call it:

  const char a[] = {'a','b','c'};
  startIndex = [self findStartIndex:buffer  searchPattern: a];

and like this

  const char b[] = {'1','2'};
  startIndex = [self findStartIndex:buffer  searchPattern: b];

But I keep getting the compiler warning:

Sending 'const char[3]' to parameter of type 'char *' discards qualifiers 

and

Sending 'const char[2]' to parameter of type 'char *' discards qualifiers 

respectively.

How to do this correctly?

Answer 1

Because the parameter you declared as char *, but const char [] is passed. It's a have a potential risk. you should the following changes. Do not have a warning when I tested.

+(int) findStartIndex: (NSData*)buffer  searchPattern: (const char*) searchPattern

Answer 2

Qualifiers in C apply to the keyword on the left first, then fallback to the right next. const char arr[] is not a constant reference to a char array, it's always of type char. But, when you pass it to a method that takes a pointer to char, then you lose the const'ness of the type, and you get a warning. (Hooray for obscure C stuff!)