Improvement: Replace func handler by std::function

[Belphemur]

Hello,

With the current definition of the func handler:

typedef bool (*handler_t)(T opaque); /* task handler func signature */

It's impossible to use std::bind when you want the timer to run a callback that is a member of the class.

by changing the definition to use std::function like

typedef std::function<bool(T opaque)> handler_t;

It should let the user use any type of supported callback and shouldn't break the current working of the library.

[kpfleming]

This is certainly true, and it would also allow the use of lambdas for callbacks, which can have benefits.

One the downside it will increase the size of the handler_t from 4 bytes to (probably) 32 bytes.

[contrem]

The other downside is that these are c++11 features, and we lose c++98 compatibility. It's worth discussing as the next planned release will likely be a major version release.

[Belphemur]

I admit I'm quite new into Arduino development, but I would argue that https://github.com/esp8266/Arduino seems to have made the move to C++11 sometimes ago.

I don't know if keeping compatibility with c++98 is still something that would make sense in 2022.

Technically, telling people that need c++98 to use a previous major version shouldn't be much of an issue, I imagine.

[kpfleming]

There are dozens of Arduino platforms that do not support C++11 and likely won't ever support it. That makes such a change for a library owner complicated, because they need to decide which platforms to support (or support both).

If you are really interested in using a 'modern C++' timer library, feel free to check out my library which was inspired by this one, but leverages C++11/14/17 features.

[skrobinson]

I'd like to see C++11 (or later) language use, but not an STL requirement.

Things that could be done with just a language update:

• auto and decltype
• constexpr
• lambda expressions
• nullptr
• range-for
• much more...

I have a fork branch that uses some of the above list.

[philj404]

FYI The Github Action at https://github.com/contrem/arduino-timer/blob/master/.github/workflows/githubci.yml
runs a build check for examples on some (not all) platforms.

We inherit much of this list from the scripts at adafruit/ci-arduino -- and so we don't have to maintain the script. As of January 2022 we get automated builds on:

SWITCHING TO arduino:avr:uno ...
SWITCHING TO arduino:avr:leonardo ...
SWITCHING TO arduino:samd:arduino_zero_native ...
SWITCHING TO adafruit:samd:adafruit_qtpy_m0 ...
SWITCHING TO esp8266:esp8266:huzzah:eesz=4M3M,xtal=80 ...
SWITCHING TO esp32:esp32:featheresp32:FlashFreq=80 ...
SWITCHING TO adafruit:samd:adafruit_metro_m4:speed=120 ...
SWITCHING TO adafruit:samd:adafruit_trinket_m0 ...
SWITCHING TO esp32:esp32:featheresp32:FlashFreq=80 ...
SWITCHING TO esp8266:esp8266:huzzah:eesz=4M3M,xtal=80 ...

• While each build is successful, there are differences in the compilers. Some platforms show more warnings than others. Warnings are ignored.
• The builds only compile the examples. If no example exercises a feature it won't be checked. (If you added a new macro, will a build verify the macro works on all platforms? You probably want an example anyway.)
• arduino-timer does work for other platforms; we just don't test them. It's a nice general-purpose library with minimal dependencies.

So really my point is just that we have quite a few variants and that we want it ALL to continue to work.

If we really need a new C++XX feature which really improves readability (or efficiency?), and is incompatible with some legacy platform, we should make a formal break. Let's make it clear which platforms need to use an earlier release of this library.

[skrobinson]

"GCC 4.8.1 was the first feature-complete implementation of the 2011 C++ standard..." -- https://gcc.gnu.org/projects/cxx-status.html#cxx11

Release dates:

• GCC 4.8.1 May 2013
• Arduino 1.6.0 (with avr-gcc-4.8.1) February 2015
• arduino-timer 0.0.1 October 2018.

How many arduino-timer-using projects have a C++98- or C++03-only language requirement? Does arduino-timer target other, older compilers? Answering these questions will help decide if a language feature is reasonable for this project.

If we really need a new C++XX feature which really improves readability

As a concrete example of a change that could be made:

- timer_foreach_const_task(task) {
+ for (const auto &task : tasks) {

I would say the readability is roughly the same, except that the first line is not what the compiler sees. One must interpret the timer_foreach_const_task macro to determine the actual code to be compiled.