PROGMEM on functions that take const char *value

Hello, trying to save RAM i converted most of my Strings using F().
However, I have a number of libs that take parameters as take const char *.

How can I convert something like:
const char URL PROGMEM = "http://www.whatever.org/data/";

into something that is digestible to:

void function(const char *value)

THANKS

Copy the PROGMEM string to a local string I
RAM just before calling the function?

Rewrite the function to accept __FlashHelperString pointers?

Thanks. The behaviour is actually weird.
If i do the following it works:

String tempStr = F("myValue");
myFunction(tempStr.c_str());

But not if i do:

myFunction(String(F("myValue")).c_str());

Any sugestions?
thanks!

To say that you're "trying to save RAM" and then use objects of the String class in the attempt do so is such an inconsistency that it boggles the mind. You should be using c-strings (null-terminated arrays of char) for this as suggested by @AWOL.