Fix for undefined reference to atexit() function.

[Chris--A]

Hi, I recently ran into an issue which is present in all branches of the IDE.

The linker fails due to a missing standard library function atexit().
This issue affects all IDE branches I have tested:

• 1.0.5-r2
• 1.5.6-r2
• 1.5.7 using C++11

The problem manifests itself when giving an object with a defined destructor, static local storage duration.

Here are two basic examples of the error:

void setup(){
  static String s;
}

void loop() {}

Its not the String libraries fault, any object that requires implicit destruction causes an error:

struct Foo{
  Foo(){}
  ~Foo(){}
};

void setup(){
  static Foo f;
}

void loop() {}

The fix I propose will allow these examples to compile, and I have tested it on the three versions of the IDE I mentioned above.

I created this patch on the master, can you automatically merge this with 1.5.x, or do I need to make a new pull request?

As a side note, if the function is moved else where, it must be declared extern "C". This is taken care of by Arduino.h

Fixes #1919

[matthijskooijman]

Code looks good to me. I do have some comments on the PR itself:

• These two commits should really be a single commit - neither of them makes sense without the other.
• You should put "Fixes atexit() called after setup() #1919" at the end of the commit message, to have github autoclose that issue.
• I'd like a little bit more explanation (in the comments in the code) as to why it's ok to have an empty exit function (i.e., because an Arduino program never actually exits, there is no need to call atexit handlers, but since the compiler inserts calls to atexit automatically, it does need to exist).

To update your pullrequest, you can apply the changes locally (if you don't know how, try running git rebase -i origin/master and be amazed about the power of rebase ;-p) and then do a forced push to your patch-3 branch to update the PR here.

I think having a PR for ide-1.5.x would also be good. The changes are fairly trivial, but when you submit a PR we can be sure the changes merged are exactly the ones you tested. However, @cmaglie has the final word on this, he's the one doing the merges.

[cmaglie]

I regularly merge master into ide-1.5.x so there is no need to create a separate patch for 1.5.

@Chris--A
If you can rewrite the commit as suggested by Matthijs it would be great!

[Chris--A]

I have tried downloading the repo on windows a couple of times without luck, I have made this request via the webpage which is why its two commits.

I'll try again to see if it will work. If it does, I'll update the PR. It mat take a few hours so I'll report back.

I will also update the pull request info too.

[Chris--A]

Every time I try and clone the repo it fails. Git-hub responds that the repo is in an unknown state and possibly corrupted. I think windows git-hub has some problems with long path names.

I can update the code comments, however it requires an additional commit when using the web page editor.

[matthijskooijman]

If you update using the editor, then either @cmaglie can manually merge and squahs the commits, or perhaps I can do it and create a new PR for it.

[cmaglie]

I've manually merged the patch, here the "squashed" commit:

1bbcb2f

Thank you!