String() class fails to construct properly with floats and doubles

[mwmckee]

Hitting an issue where using Arduino's String class constructor fails to create a string when given an initial value that is a float or a double.

Simple repro: Serial.print(String(1.1)) doesn't print anything.

A repro program is attached. This program works when targeting an Uno. This is with the following two packages installed:
◾Arduino SAMD Boards (32-bits ARM Cortex-M0+), version 1.6.2
◾Arduino SAMD Core - (build 1), version 1.6.2-build-2

string_bug_repro.txt

[mwmckee]

A workaround is to use the following line of code to force link printf's float support

asm(".global _printf_float");

[sandeepmistry]

@mwmckee I've submitted PR #111 to correct this, @arduino bot has created a build that you can try out here: #111 (comment).