I am sorry if I am sounding arrogant but I really do not understand why you guys are trying so hard to say a problem does not exist when it does.
@jremington
For your solution 1, I do not know how the "extensions enabled" work and I could not find much information on sprintf in arduino except the fact that it does not support formatting. Will be more than happy to see a link or an elaboration of your idea.
For solution number 2, you gotta be kidding. Do you actually understand how much time it takes to check the float range for every conversion? Also, if you have ever rolled your eyes on dtostrf implementation, it knows exactly what is going to happen. it knows the exponent and can easily compute and estimate the length required right after its first step which is extracting the exponent. I have done this and considering the current attitude in the community so far, I guess I end up doing it myself and making a safe version of dtostrf (which could stop when buffer length is used up and return a false), or a conditional checking using the mathematical properties of exponent (less efficient because it will happen again in side dtostrf)
@Delta_G
I think you are focusing on the meaning of the number. Where I do not even consider that as an on topic . I understand your point, but if you have a heavy calculation in your program and some variables may happen to have an unusual values then having 35 digit number is possible. Yes, the data is in accurate and all that but it has happened and probably you do not know that it has happened in your program because you did not expected the unusual value when writing the code (yes, you can be careful and check stuff but there still might be cases where the number can get screwed up) and when the dtostrf is called it starts writing on the rest of the memory where it is not supposed to. That is not something you can forgive in most cases.