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)

[LEKPHET-KUNSUE]

in fact solve it with this code block

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

[LEKPHET-KUNSUE]

try it.