Including FastLED library breaks prototype generation

[per1234]

Using Arduino IDE Beta build 25 with Windows 7 64 bit

• Install FastLED library (it's in the Library Manager index)
• Compile the following sketch (EDIT: for Arduino/Genuino Uno or other AVR board):

#include <FastLED.h>
void setup() {
  foo();
}
void loop() {}
void foo() {}

Error:

C:\Users\per\AppData\Local\Temp\arduino_modified_sketch_198423\sketch_nov21a.ino: In function 'void setup()':

sketch_nov21a:5: error: 'foo' was not declared in this scope

 void loop() {}

       ^

arduino-preprocessor -debug output:
https://gist.githubusercontent.com/per1234/e2e45e7b84de756ae1782178790c5830/raw/ecdd542f40c951ca8b93f9a585ee72366f6fcfaa/sketch_nov21a.ino.cpp

Examination of the generated .ino.cpp file shows that the foo() prototype was never generated, rather than being inserted in the wrong place.

The issue does not occur in Arduino IDE 1.8.5.

Originally reported at: http://forum.arduino.cc/index.php?topic=512898

[facchinm]

Hi @per1234 ,
thanks for spotting this; in fact, the libclang backend is failing to analyze a part of the library (it looks like it's the AVR specific macros, incidentally the ones making FastLed magic happen ) and thus it doesn't generate the prototypes.
I can think about a couple of solutions (maybe @cmaglie has some other):

• fallback on ctags when arduino-preprocessor fails (at least, in the meantime, just to avoid breaking people's sketches)
• only use user program to generate the prototypes (this should work for prototype generation if no gcc-specific macro is used, but won't provide autocomplete hints)

Anyway, comping on ARM works as expected, so we can use it as a reference. The error thrown (with --output-diagnostic) is

terminate called after throwing an instance of 'std::logic_error'
  what():  basic_string::_S_construct null not valid
Aborted (core dumped)