How to convert a NSString to long double?

I am dealing with a long double value that can have huge values.

At one time I have this number represented as NSString and I need to convert it to long double. I see that the only API I have is

[myString doubleValue];

I don't see a longDoubleValue.

Trying to convert this number using doubleValue...

long double x = (long double)[@"3765765765E933" doubleValue];

gives me inf and the number in question is a legit long double value, as these numbers can go up to 1.18973149535723176502E+4932.

How do I do that?